This document summarizes a study that evaluated whether Doppler echocardiography (DE) variables could predict congestive heart failure (CHF) in dogs with degenerative mitral valve disease (MVD) or dilated cardiomyopathy (DCM). Sixty-three dogs underwent physical exams, thoracic radiography, blood tests for natriuretic peptides, and transthoracic echocardiography. Dogs were grouped based on presence or absence of CHF. Various DE variables were analyzed to determine their ability to predict CHF, with isovolumic relaxation time (IVRT), respiration rate, and diastolic functional class found to best predict CHF in MVD dogs, and diastolic functional class

1. Detection of Congestive Heart Failure in Dogs by
Doppler Echocardiography
K.E. Schober, T.M. Hart, J.A. Stern, X. Li, V.F. Samii, L.J. Zekas, B.A. Scansen, and J.D. Bonagura
Background: Echocardiographic prediction of congestive heart failure (CHF) in dogs has not been prospectively evaluated.
Hypothesis: CHF can be predicted by Doppler echocardiographic (DE) variables of left ventricular (LV) filling in dogs with
degenerative mitral valve disease (MVD) and dilated cardiomyopathy (DCM).
Animals: Sixty-three client-owned dogs.
Methods: Prospective clinical cohort study. Physical examination, thoracic radiography, analysis of natriuretic peptides,
and transthoracic echocardiography were performed. Diagnosis of CHF was based upon clinical and radiographic findings.
Presence or absence of CHF was predicted using receiver-operating characteristic (ROC) curve, multivariate logistic and step-
wise regression, and best subsets analyses.
Results: Presence of CHF secondary to MVD or DCM could best be predicted by E : isovolumic relaxation time (IVRT)
(area under the ROC curve [AUC]50.97, P o .001), respiration rate (AUC50.94, P o .001), Diastolic Functional Class
(AUC50.93, P o .001), and a combination of Diastolic Functional Class, IVRT, and respiration rate (R2
50.80, P o .001)
or Diastolic Functional Class (AUC51.00, P o .001), respiration rate (AUC51.00, P o .001), and E : IVRT (AUC50.99,
P o .001), and a combination of Diastolic Functional Class and E : IVRT (R2
50.94, P o .001), respectively, whereas other
variables including N-terminal pro-brain natriuretic peptide, E : Ea, and E : Vp were less useful.
Conclusion and Clinical Importance: Various DE variables can be used to predict CHF in dogs with MVD and DCM.
Determination of the clinical benefit of such variables in initiating, modulating, and assessing success of treatments for CHF
needs further study.
Key words: Canine; Degenerative mitral valve disease; Dilated cardiomyopathy; NT-proBNP; Respiration rate.
Congestive heart failure (CHF) is a common and of-
ten fatal clinical syndrome in dogs characterized by
cardiac dysfunction, neurohormonal activation, sodium
and water retention, and increase in left ventricular (LV)
filling pressures (LVFP).1,2
It occurs most often second-
ary to degenerative mitral valve disease (MVD)3–5
and
dilated cardiomyopathy (DCM).4
Early recognition of
CHF is of clinical importance.5
CHF can be suspected by
clinical signs although reliability of such findings may be
limited. Thoracic radiography is the most commonly ap-
plied method for the diagnosis of CHF and is considered
the clinical ‘‘gold standard.’’6
However, radiography is
of unspecified sensitivity and specificity, especially in the
setting of combined heart and lung disease, and can
suffer from considerable observer variation.6,7
Plasma
concentration of N-terminal pro-brain natriuretic
peptide (NT-proBNP) is increased in patients with
From the Department of Veterinary Clinical Sciences, College of
Veterinary Medicine (Schober, Hart, Stern, Samii, Zekas, Scansen,
Bonagura) and the Center for Biostatistics (Li), The Ohio State
University, Columbus, OH. Presented in part at the Annual Forum of
the American College of Veterinary Internal Medicine, Montreal,
Canada, June 3–6, 2009. Dr Hart is presently affiliated with Univer-
sity of Minnesota Veterinary Medical Center, 1365 Gortner Avenue,
St Paul, MN 55108. Dr Stern is presently affiliated with Department
of Veterinary Clinical Sciences, Washington State University, 100
Grimes Way, Pullman, WA 99164. This work was completed at The
Ohio State University, Columbus, OH.
Corresponding author: Karsten E. Schober, DVM, PhD, Department
of Veterinary Clinical Sciences, College of Veterinary Medicine, The
Ohio State University, 601 Vernon L. Tharp Street, Columbus, OH
43210; e-mail: schober.4@osu.edu.
Submitted December 21, 2009; Revised June 30, 2010;
Accepted July 20, 2010.
Copyright r 2010 by the American College of Veterinary Internal
Medicine
10.1111/j.1939-1676.2010.0592.x
Abbreviations:
Aduration duration of the late diastolic transmitral flow wave
Ao aortic annular dimension
ARduration duration of the late diastolic pulmonary vein atrial re-
versal flow wave
AUC area under the ROC curve
CHF congestive heart failure
CV coefficient of variation
DCM dilated cardiomyopathy
DE Doppler echocardiography
DTE deceleration time of the early diastolic transmitral flow
FAC fractional area change
IVRT isovolumic relaxation time
LA left atrial
LAAmax maximum left atrial area
LAAmin minimum left atrial area
LADmax maximum left atrial dimension
LADmin minimum left atrial dimension
Lat lateral
LV left ventricular
LVDd left ventricular internal dimension in diastole
LVDs left ventricular internal dimension in systole
LVFP left ventricular filling pressure
MVD degenerative mitral valve disease
NT-proANP N-terminal pro-atrial natriuretic peptide
NT-proBNP N-terminal pro-brain natriuretic peptide
Peak A peak velocity of late diastolic transmitral flow
Peak E peak velocity of early diastolic transmitral flow
Peak Ea peak velocity of early diastolic mitral annular motion
of the mitral annulus
Peak TR peak velocity of tricuspid regurgitation
Peak Vp peak velocity of propagation of early transmitral flow
ROC receiver-operating characteristic
Sept septal
SF shortening fraction
J Vet Intern Med 2010;24:1358–1368

2. advanced MVD and DCM and may be useful in the
diagnosis of CHF.4,5,8–11
However, a wide overlap of cir-
culating NT-proBNP concentrations in dogs with and
without CHF has been reported and generally accepted
discrimination limits have not been determined.5,8,12
In
addition, effects of renal function, day-to-day variability,
and considerable turn-around time make this variable
poorly suited for situations where bedside decisions are
immediately required.
The development of cardiogenic pulmonary edema is
predicted largely by the magnitude of volume overload
and resulting increase in LVFP.2,13,14
A simple but quant-
ifiable noninvasive method for estimation of volume
status and filling pressures could not only refine the di-
agnosis, but also promote the early recognition of CHF,
advance optimal medical management, and facilitate
therapeutic monitoring. The recent introduction of novel
Doppler echocardiographic (DE) techniques has sparked
considerable interest in the noninvasive prediction of
CHF by DE.15–19
One variable, the ratio between peak
velocity of early diastolic transmitral flow (Peak E) to
peak early tissue Doppler mitral annulus velocity
(Peak Ea; E : Ea), has gained the most attention in the
prediction of LVFP in dogs15–17,20,21
and people.18,22
Previous validation studies15,16
in experimental dogs
reported on the use of isovolumic relaxation time (IVRT)
and the ratio between Peak E to IVRT (E : IVRT) in the
diagnosis of increased LVFP. These variables, however,
have not been validated in dogs with naturally acquired
heart disease.
Therefore, we undertook a study to test the hypothesis
that DE indices of LV filling would predict CHF in dogs
with spontaneous heart failure with clinically acceptable
accuracy. More specifically, we hypothesized that E : Ea,
E : IVRT, and IVRT would be most predictive of high
CHF scores in dogs with MVD and DCM.
Materials and Methods
The study protocol was reviewed and approved by the
Institutional Animal Care and Use Committee (protocol
#2004A0196) and the Review Board of the Department of
Veterinary Clinical Sciences, College of Veterinary Medicine, The
Ohio State University, Columbus, OH.
Dogs, Clinical Examinations, and Group Assignment
Sixty-three client-owned dogs were prospectively studied. Dogs
were consecutively selected over a time period of 2 years (2007 and
2008) based upon the echocardiographic diagnosis of MVD3,23
and
DCM.24
All dogs underwent a thorough physical examination, a
noninvasive measurement of systolic blood pressure,a
thoracic radi-
ography,b,c,d,e
blood biochemical analyses, and a 2-dimensional
(2D), M-mode, and DE study.f
Heart rate and respiration rate were
taken during initial physical examination without consideration
of ambient temperature and determined as the number of beats or
respirations per minute, respectively. If respiration rate could not
be obtained due to panting, dogs were reassessed within 1 hour of
arrival in order to obtain a definitive rate. Dogs with atrial flutter
and fibrillation, arrhythmogenic right ventricular cardiomyopathy,
systemic hypertension (systolic blood pressure 4170 mmHg),
and evidence of concomitant diseases or conditions such as
hypothyroidism, renal failure, primary tracheal or pulmonary dis-
ease, anemia, or cancer were excluded. Using clinical, radiographic,
and echocardiographic data, dogs were divided into 4 groups for
statistical analyses: MVD or DCM with or without evidence of
CHF (Groups 1–4), respectively. In preclinical (asymptomatic) dogs
with MVD (Group-1), no treatments other than an ACE inhibitor
were permitted. In dogs with asymptomatic DCM (Group-3), no
treatments other than an ACE inhibitor, spironolactone, carvedilol,
and pimobendan were permitted. In dogs with CHF (MVD, Group-
2; DCM, Group-4), no treatments other than an ACE inhibitor,
spironolactone, carvedilol, pimobendan, and furosemide (given
within 12 hours of thoracic radiographs and echocardiography)
were permitted. Dogs with signs of CHF were sedated upon arrival
at the hospital with acepromazineg
(0.025–0.050 mg/kg, IM; n 5 2),
butorphanolh
(0.15–0.25 mg/kg, IM; n 5 21), or a combination of
both drugs (n 5 7).
Thoracic Radiography
Thoracic radiographs were taken in 3 different imaging planes
(right lateral, left lateral, and ventral dorsal projections) before
echocardiography. Radiographs were assessed by the attending cli-
nician only after the echocardiographic exam was performed. If
noncardiac disease or cardiac disease other than MVD and DCM
were observed, dogs were disqualified from the study. For final
radiographic diagnosis and definitive group assignment (CHF
absent or CHF present), radiographic images were reassessed by 2
independent board-certified radiologists (V.F.S. and L.J.Z.) en bloc
at the end of the case recruitment period. All 63 studies were ordered
randomly and coded by the principal investigator. The radiologists
were aware of the 2 principal diagnoses (MVD and DCM); how-
ever, they were blinded to the animal’s identification, the date of the
examination, the initial interpretation of the images, the results of
natriuretic peptide analysis, echocardiographic findings, the clinical
diagnosis, and each other’s assessment. A radiographic composite
CHF score including criteria for left atrial (LA) enlargement,
pulmonary venous congestion, pulmonary infiltrates compatible
with cardiogenic edema, and pleural effusion was used (Appen-
dix 1).i,25
The final radiographic assessment revealed a numerical
radiographic CHF score and a qualitative, binary variable (CHF
absent or CHF present). For group assignment, only the latter vari-
able was used. To assure proper application of suggested diagnostic
criteria and thus consistency of data, investigators met for a 1-hour
training session before final analysis by mock radiographic images.
After interpretation of films, results of the 2 readers were compared.
If there was disagreement with regard to the principal diagnosis
(CHF absent or CHF present), the investigators collectively reas-
sessed the images in question to come up with a final definitive
diagnosis that satisfied both raters. Intraobserver reproducibility
of the radiographic diagnosis of CHF was determined by 15 studies
(7 from dogs with compensated disease and 8 from dogs with CHF)
interpreted 3 times by 1 blinded observer (V.F.S.) using a random
order list.
Collection of Blood and Analysis of
Natriuretic Peptides
In each dog, 5 mL of blood were collected from a jugular vein
directly into serum tubes. After 20 minutes of storage at room tem-
perature (22–241C) to allow for stable clot formation, samples were
centrifuged at 3,000 g for 10 minutes at 51C and further processed
within 15 minutes. The supernatant (serum) was harvested, divided
into four 0.5 mL aliquots, transferred into plastic cryotubes, and
stored at 801C for a maximum of 4 weeks until analysis. Two
aliquots of each sample were shipped on dry ice to the reference
laboratoryj
where batched analysis was done once a month. Assays
1359
Congestive Heart Failure in Dogs

3. were run in duplicate, and the average of the 2 values was used for
final data analysis.
Serum N-terminal pro-atrial natriuretic peptide (NT-proANP)
and serum NT-proBNP were analyzed with commercial test kits
(sandwich enzyme immunoassays) with antibodies raised against
human NT-proANP31-67k,26
and canine NT-proBNP25-41 (cap-
ture antibody) and canine NT-proBNP1-22 (detection antibody).l
The detection limits were 50 pmol/L for the NT-proANP assay and
42 pmol/L for the NT-proBNP assay. The intra-assay coefficients
of variation (CV) were below 10% for the NT-proANP assay
and below 15% for the NT-proBNP assay as reported by the
manufacturer.
Echocardiography
Transthoracic 2D, M-mode, and DE examinations were per-
formed by a single operator (K.E.S.; n 5 53) or under direct
supervision of the principal investigator (n 5 10) with the dogs in
right and left lateral recumbency with a digital ultrasound systemf
with a transducer array of 3.5 MHz nominal frequency as recently
described.15
Right parasternal standard views optimized for the LA,
the LV outflow tract (long axis), or the LV (short axis) and left api-
cal parasternal standard views optimized for the LV inflow tract,
longitudinal motion of the lateral and septal mitral annulus, or the
LV outflow tract were used for data acquisition. 2D cine loops and
Doppler tracings were recorded and stored on the internal hard
drive of the echocardiograph or on magneto-optical disc and ana-
lyzed off-line. A simultaneous 1-lead ECG was recorded. Heart rate
was determined from the preceding R-R interval on the ECG and
represents the mean of 5–12 calculations. Measurements were
obtained from digital still images as an average of 5–12 consecutive
cardiac cycles, irrespective of respiratory phase. Only high-quality
images were used for data analysis. All measurements were
done off-line by 1 trained investigator (T.M.H.) blinded to the dogs’
identification, clinical signs, thoracic radiographs, and hemodynamic
status and verified by the principal investigator (K.E.S.).
Echocardiographic Data Analysis
Fourteen variables were measured and 10 variables were calcu-
lated as recently described in dogs.15,16,27
In brief, from right
parasternal long-axis recordings, the maximum (LADmax) and min-
imum (LADmin) septal-to-posterior dimension of the LA,27
the
maximum (LAAmax) and minimum (LAAmin) area of the LA, and
the end-diastolic dimension of the aortic valve (Ao) were measured
using imaging views optimized for the LA or the LV outflow tract
and inner edge projections. From a LV short-axis M-mode record-
ing at the level of the chordae tendineae, LV dimensions in systole
(LVDs) and diastole (LVDd) were measured. From the left apical 3-
chamber view, IVRT was measured as the time period from the
Doppler signal of aortic valve closure to the beginning of the trans-
mitral early diastolic flow wave (E wave) with a pulsed wave sample
volume of 6–10 mm placed in an intermediate position between the
LV inflow and outflow tracts. Transmitral flow was recorded from
the left apical 2-chamber view with a pulsed wave sample volume
(2 mm in width) placed between the tips of the opened mitral valve
leaflets. Peak E and the peak velocity of the late diastolic transmitral
flow wave (Peak A) were measured. Deceleration time of the early
diastolic transmitral flow (DTE) was measured as the time from
Peak E velocity to the end of E at the baseline. Summated E and A
waves were not measured. Duration of the A wave (Aduration) was
measured from the beginning to the end of the A wave. Pulmonary
venous flow was recorded from the same left apical 2-chamber view,
with minimized baseline filter, optimized velocity scale, and with a
pulsed wave sample volume of 4–6 mm placed 5–10 mm within the
pulmonary vein of the left caudal lung lobe.28
Only the duration of
the late diastolic reversal wave (ARduration) was measured. Pulsed-
wave Doppler-derived velocities of myocardial motion were
recorded from an apical 2-chamber view, with a sample volume of
5–6 mm placed in the septal or lateral aspects of the mitral annulus.
Frame rate during tissue Doppler studies was optimized (4160
frames per second) by narrowing the imaging sector. Peak velocity
of early diastolic septal (Peak Ea Sept) and lateral (Peak Ea Lat)
mitral annulus motion was measured. Color M-mode recordings of
early diastolic LV inflow were used to determine LV flow propaga-
tion velocity (Peak Vp). Color Doppler transmitral flow recordings
were obtained, the Nyquist limit was reduced to approximately 50%
of Peak E, and the slope of the 1st aliasing velocity line from the tip
of the mitral valve to 3 cm distally into the LV cavity was used for
determination of Peak Vp.29
From a right parasternal tilted short-
axis view or a left apical cranial view optimized for the right ven-
tricular inflow tract, peak tricuspid regurgitation (Peak TR) velocity
was recorded. A Peak TR velocity of 3.0 m/s was considered an
echocardiographic finding suggestive of mild to severe pulmonary
hypertension.30,31
Variables calculated included LA shortening frac-
tion (SF; LA-SF 5 [LADmax LADmin]/LADmax 100%), LA
fractional area change (LA-FAC 5 [LAAmax LAAmin]/LAAmax
100%), the LA-to-Ao ratio (LADmax : Ao), LV shortening frac-
tion (LV-SF 5 [LVDd LVDs]/LVDd 100%), the ratio between
Peak E (cm/s) to IVRT (ms; E : IVRT); the ratio between Peak E to
Peak A (E : A); the ratio between the duration of A to the duration
of AR (Aduration : ARduration), the ratios between Peak E to Peak
Ea Sept (E : Ea Sept), Peak E to Peak Ea Lat (E : Ea Lat), and Peak
E to Peak Vp (E : Vp), and [(E : Ea Lat) 1 (E : Ea Sept)]/2. LV dia-
stolic function was classified22
based on E : A and qualified based on
E : Ea Lat Class-1: Normal pattern (1.0 E : A 2.0), Class-2:
Relaxation delay pattern (E : A o 1.0), Class-3: Pseudonormal
pattern (1.0 E : A 2.0), and Class-4: Restrictive pattern (E :
A 4 2.0). Class-1 and Class-3 were discriminated using cut-offs of
E : Ea Lat of 11.0 for dogs with MVD and 9.0 for dogs with DCM.
These discrimination values were obtained from a previous pilot
study of 25 dogs with DCM and 52 dogs with MVD.m,32
In dogs
older than 10 years, any observed E : A between 1.0 and 2.0 was
considered pseudonormal transmitral flow because of the fact that a
physiologic age-related relaxation delay pattern would be expected
in such dogs.33
Measurement reliability was determined for selected echocardio-
graphic variables. Four echocardiograms each from dogs with
MVD and DCM were randomly selected from the pool of studies
to undergo 5 repeated analyses by 1 observer (T.M.H.) to determine
intraobserver measurement variability. The same 8 echocardio-
grams underwent repeated analyses by a 2nd independent observer
(K.E.S.) to determine interobserver measurement variability. Both
investigators were blinded to the results of prior studies.
Statistical Analyses
Statistical analyses were done with commercially available soft-
ware.n,o,p
All continuous outcome variables were visually inspected
and tested for normality by the Kolmogorov-Smirnov test. Descrip-
tive statistics were determined: frequencies for categorical variables
and median and 5 and 95 percentiles for continuous variables. Se-
lected data were graphically depicted as median and scatter plot of
individual data points. Groups of dogs with MVD (Group-1 versus
Group-2) and DCM (Group-3 versus Group-4) were compared us-
ing an unpaired t-test if standard assumptions were fulfilled or the
Mann-Whitney rank-sum test if not. Proportions were compared by
Fisher’s exact test. Receiver-operating characteristic (ROC) curve
analysis was used to determine the diagnostic ability of heart rate
(taken at physical examination), respiratory rate, NT-proANP, NT-
proBNP, and various DE variables in the diagnosis of CHF and to
define optimal discrimination limits (diagnostic cut-off values) for
such prediction. The area under the ROC curve (AUC) was used as a
summary measure for diagnostic accuracy and to quantify the ability
1360 Schober et al

4. of variables to predict CHF and is reported with 95% confidence in-
tervals. Cut-off values were chosen based on the highest Youden
index (Y 5 (Se 1 Sp) 1) of various combinations of Se and Sp.34
Multivariate logistic regression was used to predict the qualitative
dichotomous variable ‘‘CHF absent or CHF present’’ (based on ra-
diographic diagnosis) from observations of 1 or more independent
variables by fitting a logistic function to the data. In addition to all
tabulated variables, variables such as prior treatment with furose-
mide and presence of azotemia were also considered in the
regression. Once variables with significant (P o .05) associations
were identified, forward selection and best subsets regression ana-
lyses were performed to identify the combination of variables that
predicted presence of CHF best and to determine the contribution of
individual variables to the final model. For model fitting, a 1 : 7 ap-
proach was used (ie, addition of no more than 1 independent
variable to the model for every 7 observations).
Conformity among observers with regard to radiographic inter-
pretation of recordings after 1st assessment were determined by the
nonparametric McNemar’s test,35
Bowker’s test of symmetry,36
and
by calculating Cohen’s Kappa coefficients (k).37
Intraobserver repro-
ducibility of the radiographic diagnosis of CHF was determined by 1-
way random effects models for calculation of the intraclass
correlation coefficient (ICC).38
Observer variability of echocardio-
graphic measurements was calculated by coefficients of variation (CV
5 [standard deviation / average of measurements] 100) and ex-
pressed as CV in percent and also as absolute value of the respective
variable.39
For all analyses, P-values .05 were considered significant.
Results
Demographic data, historical findings, and results of
physical examination and blood pressure measurement
are summarized in Table 1. At presentation, 11 (52%)
dogs of Group-1 and 10 (42%) dogs of Group-2 were on
long-term treatment with enalapril or benazepril. In
Group-2, 12 (50%) had received furosemide within the
last 12 hours before the study; however, they were still
diagnosed with CHF at the time of thoracic radiography
and echocardiography. At presentation, 1 (9%) dog of
Group-3 and 2 (28%) dogs of Group-4 were on long-
term treatment with enalapril or benazepril. In Group-4,
2 (28%) dogs had received furosemide within the last 12
hours before the study; however, they were still diag-
nosed with CHF at the time of thoracic radiography and
echocardiography. Azotemia was detected in 1/10 dogs
of Group-1, 5/24 dogs of Group-2, and no dogs in
Group-3 or Group-4. In all dogs, BUN was o50 mg/dL
(reference range, 5–20 mg/dL) and creatinine was
o2.7 mg/dL (reference range, 0.6–1.6 mg/dL).
Results on radiographic composite score, NT-
proANP, and selected echocardiographic variables are
presented in Table 2. One dog of Group-1 and 2 dogs of
Group-2 had a radiographic composite score of 4.0. All
other dogs were either below 4.0 (Group-1) or above 4.0
(Group-2). Two dogs of Group-3 had a radiographic
composite score of 4.0. All other dogs were either below
4.0 (Group-3) or above 4.0 (Group-4). The minority of
dogs with compensated heart disease (15% in Group-1
and 27% in Group-3) and the majority of dogs with CHF
(71% in Group-2 and 86% in Group-4) had echocardio-
graphic evidence of mild to severe pulmonary
hypertension using a diagnostic cut-off of 3.0 m/s Peak
TR velocity for estimation.30,31
Summated E and A
waves seen in 2 dogs with MVD were discarded from
further data analysis.
Figures 1 and 2 illustrate median and scatter plots of
respiration rate, NT-proBNP, E : A, Diastolic Func-
tional Class, IVRT, E : IVRT, E : Ea Lat, and
Aduration : ARduration in dogs with MVD (Fig 1) and
DCM (Fig 2) and differences between dogs with com-
pensated disease (Group-1 and Group-3) and dogs with
CHF (Group-2 and Group-4).
Table 1. Demographic data and results of history, physical examination, and blood pressure measurement in 63 study
dogs.
Group-1 Group-2 Group-3 Group-4
n 21 24 11 7
Number of different breeds 10 14 5 5
Most common breed (n) CKCS (9) CKCS (4) Doberman (5) Doberman (4)
Age (years) 10 (6–12) 10 (7–13) 6 (1–13) 7 (5–12)
Body weight (kg) 11 (5–37) 10 (4–36) 32 (11–58) 37 (30–54)
Sex (female : male) 1.10 0.85 1.20 0.75
Exercise intolerance (%) 10 100z
18 100
Cough (%) 43 84z
0 86
Tachypnea and dyspnea (%) 0 75z
9 71
Syncope and near-syncope (%) 0 29z
9 14
Respiration rate (per minute) 28 (19–57) 54 (38–85)z
26 (20–32) 56 (36–60)
Heart rate (per minute) 132 (91–169) 140 (100–206) 114 (70–198) 160 (120–210)
Systolic heart murmur (%) 100 100 91 100
Murmur grade (0/6–6/6) 3 (2–6) 4 (3–6)z
2 (0–3) 2 (1–3)
Systolic blood pressure (mmHg) 130 (97–160) 125 (90–156) 131 (112–170) 113 (90–128)
Group-1, degenerative mitral valve disease (MVD) without congestive heart failure (CHF); Group-2, MVD with CHF; Group-3, dilated
cardiomyopathy (DCM) without CHF; Group-4, DCM with CHF. Median (5 and 95 percentiles) for continuous data and number (n) or
percent (%) for frequency data.
Within a row, values between Group-3 and Group-4 differ significantly (P .05).
z
Within a row, values between Group-1 and Group-2 differ significantly (P .05).
1361
Congestive Heart Failure in Dogs

5. In dogs with MVD, DTE (P 5 .59), heart rate taken at
physical exam (P 5 .39), Aduration : ARduration (P 5
.79), Peak Vp (P 5 .98), and SF (P 5 .69) did not predict
presence of CHF (Tables 3 and 4). In dogs with DCM,
NT-proANP (P 5 .89) and Peak Vp (P 5 .87) did not
predict presence of CHF.
Regression analyses revealed that presence of CHF in
dogs with MVD can be predicted from a combination of
Diastolic Functional Class (step 1, R2
5 0.58, P o .001),
IVRT (step 2, cumulative R2
5 0.72, P o .001), and res-
piration rate (step 3, cumulative R2
5 0.80, P o .001)
leading to the general prediction model: CHF 5 X 1
(0.190 Diastolic Functional Class) (0.0104 IVRT [ms])
1 (0.00935 Respiration Rate [per minute]). With the
same methods in dogs with DCM, presence of CHF
could be predicted from a combination of Diastolic
Functional Class (step 1, R2
5 0.91, P o .001) and
E : IVRT (step 2, cumulative R2
5 0.94, P 5 .021) leading
to the general prediction model: CHF 5 X 1 (14.273 Di-
astolic Functional Class) 1 (0.843 E : IVRT).
Kappa (k) for assessment of conformity between the
2 radiographic observers was 0.78 (95% CI, 0.70–0.86)
for LA enlargement; 0.44 (95% CI, 0.32–0.55) for
pulmonary infiltrates compatible with cardiogenic ede-
ma; 0.26 (95% CI, 0.05 to 0.56) for pleural effusion;
0.37 (95% CI, 0.21–0.52) for pulmonary venous conges-
tion; and 0.65 (95% CI, 0.52–0.78) for the final diagnosis
of CHF. Consistency of 1 radiographic observer (V.F.S.)
in the diagnosis of CHF based on ICC was 0.92.
Results of studies on measurement variability of echo-
cardiographic indices are summarized in Table 5.
Coefficients of variation for intra- and interobserver mea-
surement variability were o10 % for all but 3 variables.
Discussion
Increase in filling pressure is a unifying feature of CHF
regardless of underlying cause.2,13
Because filling pres-
sure cannot be directly measured in clinical situations; an
easily applicable, reliable, noninvasive method is needed.
Results of this study support the contention that CHF
secondary to MVD and DCM can be predicted by DE.
The major finding is that E : IVRT, Diastolic Functional
Class, and IVRT allow for a rapid and feasible estima-
tion of whether or not CHF is present. In addition,
respiration rate taken at physical exam was equally use-
ful in the prediction of CHF. Moreover, disease-specific
differences between dogs with MVD or DCM regarding
the diagnostic accuracy of individual DE variables and
clinical decision thresholds were identified and thus need
to be considered clinically.
Diagnosis of CHF by Single DE Variables
Our results are in agreement with previous findings
from studies in anesthetized, volume loaded dogs16
and
dogs with rapid pacing-induced CHF.15
In the former16
in which mean LA pressure was measured directly,
E : IVRT outperformed 8 commonly used DE variables
of filling pressure and predicted increased LA pressure
(15 mmHg) with high accuracy. In the latter,15
a de-
crease of LV end-diastolic pressure after furosemide was
best predicted by a decrease of E : IVRT. In both stud-
ies,15,16
neither E : Ea nor E : Vp was diagnostically
useful in the prediction of increased LVFP. The ratio-
nale behind the use of combined indices such as
E : IVRT, but also E : Ea and E : Vp, is to ‘‘correct’’ for
Table 2. Radiographic score, serum concentrations of NT-proANP, and selected echocardiographic variables in 63
study dogs.
Group-1 Group-2 Group-3 Group-4
n 21 24 11 7
Radiographic composite score 1 (0–4) 7 (4–9)z
1 (1–4) 7 (5–8)
NT-proANP (pmol/L) 362 (151–980) 941 (325–3,035)z
565 (120–1,644) 542 (234–990)
LADmax : Ao 2.23 (1.80–3.12) 3.19 (2.31–4.23)z
2.18 (1.53–2.66) 2.81 (2.51–3.60)
LA-FAC (%) 37 (17–49) 24 (10–43)z
26 (18–43) 11 (5–34)
LA-SF (%) 20 (7–28) 11 (5–23)z
15 (8–27) 6 (3–19)
LV-SF (%) 39 (24–55) 43 (24–59) 21 (10–25) 16 (10–23)
TR (%) 86 92 91 86
Peak TR (m/s) 2.81 (2.19–3.15) 3.43 (2.08–4.61) 2.77 (2.18–3.46) 3.18 (2.28–3.83)
TR 4 3 m/s (%) 15 71z 27 86
Peak E (m/s) 0.92 (0.60–1.45) 1.41 (1.04–1.74)z
0.80 (0.54–1.02) 1.39 (0.70–1.74)
DTE (ms) 88 (65–112) 86 (62–120) 100 (64–128) 62 (57–104)
Peak Vp (cm/s) 51 (30–95) 52 (38–87) 33 (23–48) 33 (28–43)
E : Vp 1.66 (0.88–3.94) 2.63 (1.36–3.77)z
2.17 (1.41–3.56) 3.63 (2.47–4.56)
Peak Ea Lat (cm/s) 10.1 (6.3–16.1) 8.7 (6.2–17.4) 10.3 (6.7–17.7) 8.54 (6.7–17.1)
Peak Ea Sept (cm/s) 8.82 (5.16–14.16) 9.80 (5.49–15.10) 7.37 (5.57–16.54) 7.08 (5.55–12.52)
E : Ea Sept 10.6 (6.7–16.6) 14.7 (7.6–22.8)z
9.4 (5.9–13.2) 14.9 (8.7–24.6)
[(E : Ea Sept) 1 (E : Ea Lat)]:2 10.0 (6.5–15.1) 14.4 (6.1–22.3)z
8.4 (4.2–11.0) 15.2 (8.9–22.5)
NT-proANP, N-terminal pro-atrial natriuretic peptide; LADmax, maximum left atrial dimension; Ao, aortic annular dimension; FAC,
fractional area change; SF, shortening fraction; Peak TR, peak velocity of tricuspid regurgitation; Peak E, peak velocity of early transmitral
flow; Peak Vp, peak velocity of propagation of early transmitral flow; Peak Ea, peak velocity of early diastolic mitral annular motion; Lat,
measured at the lateral mitral annulus; septal, measured at the septal mitral annulus.
See Table 1 for key.
Median (5 and 95 percentiles) for continuous data and number (n) or percent (%) for frequency data.
1362 Schober et al

6. the effect of relaxation on a variable that is largely de-
pendent on filling pressure, but also influenced by
relaxation. By combining Peak E, a variable that is de-
termined mainly by filling pressure and relaxationn,18,40,41
with a variable that is most dependent on relaxation
(eg, IVRT, Peak Ea, and Peak Vp),18,40
the effect of
Group-1 Group-2
0
10
20
30
40
50
60
70
80
90
100
Respiration
Rate
(min
–1
)
Group-1 Group-2
0
1
2
3
4
E:A
Group-1 Group-2
0
1000
2000
3000
4000
5000
6000
7000
NT-proBNP
(pmol/L)
Group-1 Group-2
0
1
2
3
4
Class
of
LV
Diastolic
Function
Group-1 Group-2 Group-1 Group-2
0
10
20
30
40
50
60
70
80
IVRT
(ms)
0
1
2
3
4
5
6
7
8
9
10
E:IVRT
Group-1 Group-2
0
5
10
15
20
25
E:Ea
lat
Group-1 Group-2
0.00
0.25
0.50
0.75
1.00
1.25
1.50
1.75
2.00
A
duration:AR
duration
Fig 1. Medians and scatter plots of respiration rate, NT-proBNP,
and Doppler echocardiographic variables of left ventricular (LV)
filling in 21 dogs with compensated degenerative mitral valve disease
(MVD; Group-1) and 24 dogs with MVD and congestive heart fail-
ure (Group-2). Respiration rate (median, 28 versus 54 bpm, P o
.001); NT-proBNP (median, 848 versus 2,750 pmol/L, P o .001);
E : A ratio (median, 1.34 versus 2.21, P o .001); Class of LV Dia-
stolic Function (median, 1 versus 4, P o .001); isovolumic
relaxation time (IVRT) (median, 57 versus 36 ms, P o .001);
E : IVRT ratio (median, 1.74 versus 3.71, P o .001); E : Ea (median,
8.9 versus 15.2, P o .001); and Aduration : ARduration ratio (me-
dian, 1.30 versus 1.26, P 5 .79).
Group-3 Group-4
10
20
30
40
50
60
70
80
90
100
Respiration
Rate
(min
–1
)
Group-3 Group-4
0
1000
2000
3000
4000
5000
6000
7000
NT-proBNP
(pmol
/
L)
Group-3 Group-4
0
1
2
3
4
E:A Group-3 Group-4
0
1
2
3
4
Class
of
LV
Diastolic
Function
Group-3 Group-4
0
10
20
30
40
50
60
70
80
90
IVRT
(ms)
Group-3 Group-4
0
1
2
3
4
5
6
7
8
9
10
E:IVRT
Group-3 Group-4
0
5
10
15
20
25
E:Ea
lat
Group-3 Group-4
0.00
0.25
0.50
0.75
1.00
1.25
1.50
1.75
2.00
A
duration:AR
duration
Fig 2. Medians and scatter plots of respiration rate, NT-proBNP,
and Doppler echocardiographic variables of left ventricular (LV) fill-
ing in 11 dogs with compensated dilated cardiomyopathy (DCM;
Group-3) and 7 dogs with DCM and congestive heart failure (Group-
4). Respiration rate (median, 26 versus 56bpm, P o .001); NT-pro-
BNP (median, 1,314 versus 3,830 pmol/L, P o .001); E :A ratio
(median, 1.10 versus 2.73, P o .001); Class of LV Diastolic Function
(median, 1 versus 4, P o .001); isovolumic relaxation time (IVRT)
(median, 66 versus 32ms, P o .001); E:IVRT ratio (median, 1.11
versus 4.41, P o .001); E :Ea (median, 7.9 versus 13.3, P 5 .003); and
Aduration :ARduration ratio (median, 1.47 versus 0.73, P o .001).
1363
Congestive Heart Failure in Dogs

7. relaxation on Peak E can be minimized. Because increased
filling pressure, a main hemodynamic characteristic of
CHF,2,13
is associated with both increased Peak E and de-
creased IVRT,13,14,19,21,41
the ratio of E : IVRT should be
high in dogs with CHF and low in dogs with compensated
heart disease.14
The latter was confirmed in this study for
both dogs with MVD or DCM.
The IVRT is an index of relaxation and is linearly re-
lated to tau, the time constant of LV isovolumic
relaxation. However, it is also influenced by a multitude
of other factors including preload, afterload, heart rate,
and age.13,14
Therefore, IVRT represents the net effect of
many determinants, only one of which is relaxation.42
Whereas a mild increase in LVFP as seen in the early
stages of heart failure shortens tau (ie, improves relax-
ation) but is not associated with shortening of IVRT,
moderate and severe increase in filling pressure as seen in
CHF prolongs tau (ie, makes relaxation worse) but
shortens IVRT in a linear manner.13,14,41,42
Shortened
IVRT is by definition an integral part of restrictive LV
filling, a transmitral flow pattern considered specific for
advanced diastolic dysfunction, high filling pressure, and
CHF.13,41,43
That is, high filling pressure can minimize
the effect of relaxation on IVRT, turning it into a more
specific indicator of LVFP and thus CHF.42
This was
confirmed in our study, in particular in dogs with DCM.
Both IVRT and Peak E (and thus E : IVRT) are relatively
easy to measure DE variables and might provide, in
concert with historical and clinical findings, immediate
information on heart failure status in dogs with DCM or
MVD.
The E :Ea ratio and the E: Vp ratio have been reported
to be useful DE indices of LVFP and CHF in clinical
trials in people19,40
with E: Ea preferred by most.18,19
Although studies on the use of such variables in experi-
mental dogs are numerous,15,16,20,21,29
data on dogs with
Table 3. Areas under the receiver-operating characteristic curve (AUC) and optimal diagnostic cut-offs of clinical
and echocardiographic variables in the prediction of congestive heart failure in 45 dogs with degenerative mitral valve
disease.
AUC 95% CI Cut-off Se Sp P
E : IVRT 0.97 0.92–1.02 2.50 0.92 0.96 o .001
Respiration rate (per minute) 0.94 0.84–1.04 41 0.92 0.94 o .001
Diastolic Functional Class 0.93 0.85–1.01 2 0.92 1.00 o .001
LA : Ao 0.90 0.81–0.99 2.52 0.92 0.81 o .001
E : A 0.89 0.78–0.99 1.58 0.87 0.86 o .001
Peak E (m/s) 0.87 0.77–0.98 1.08 0.96 0.71 o .001
IVRT (ms) 0.86 0.75–0.98 46 0.88 0.76 o .001
E : Ea Lat 0.83 0.70–0.95 11.5 0.75 0.91 o .001
NT-proBNP (pmol/L) 0.83 0.75–0.98 1,951 0.75 0.86 o .001
NT-proANP (pmol/L) 0.83 0.71–0.95 584 0.78 0.71 o .001
[(E : Ea Lat) 1 (E : Ea Sept)]/2 0.79 0.64–0.93 12.4 0.74 0.86 .001
E : Vp 0.75 0.61–0.90 1.87 0.79 0.62 .004
E : Ea Sept 0.74 0.59–0.90 14.7 0.55 0.95 .006
CI, confidence interval; Se, sensitivity; Sp, specificity.
See Table 2 for key.
Table 4. Areas under the receiver-operating characteristic curve (AUC) and optimal diagnostic cut-offs of clinical and
echocardiographic variables in the prediction of congestive heart failure in 18 dogs with dilated cardiomyopathy.
AUC 95% CI Cut-off Se Sp P
Diastolic Functional Class 1.00 1.00–1.00 2 1.00 1.00 o .001
Respiration rate (per minute) 1.00 1.00–1.00 34 1.00 1.00 o .001
E : IVRT 0.99 0.95–1.03 1.88 1.00 0.91 o .001
IVRT (ms) 0.98 0.93–1.03 43 1.00 0.91 o .001
Aduration : ARduration 0.98 0.93–1.04 1.25 1.00 0.90 o .001
E : A 0.97 0.89–1.05 2.0 1.00 0.90 .002
E : Vp 0.95 0.85–1.05 3.56 0.86 0.90 .002
E : Ea Lat 0.94 0.82–1.05 9.0 1.00 0.73 .002
NT-proBNP (pmol/L) 0.94 0.83–1.05 2,492 1.00 0.82 .002
[(E : Ea Lat) 1 (E : Ea Sept)]/2 0.94 0.82–1.06 11.0 0.86 1.00 .002
DTE (ms) 0.91 0.76–1.06 72 0.86 0.90 .005
Peak E (m/s) 0.89 0.69–1.09 1.05 0.83 1.00 .008
E : Ea Sept 0.87 0.68–1.07 13.9 0.71 1.00 .013
LA : Ao 0.86 0.69–1.03 2.46 1.00 0.73 o .001
HR (per minute) 0.83 0.60–1.06 135 0.71 1.00 .021
SF (%) 0.79 0.57–1.00 19 0.71 0.82 .046
See Tables 2 and 4 for key.
1364 Schober et al

8. naturally acquired heart disease are sparse and its diag-
nostic value largely unproven.m,44
Both Ea and Vp have
been shown to be relatively preload-independent indices
of LV relaxation, making them suitable for correcting
Peak E for the effects of relaxation.18,40
In healthy dogs,
Vp and even more Ea are dependent on ‘‘lengthening
load’’ (load that the myocardium experiences during
relaxation).15,16,20,21,45
Absence of diastolic abnormali-
ties primarily concerning myocardial relaxation and
chamber compliance, typically seen in dogs with MVD,1
are potential reasons why Ea is sensitive to changes in
preload under such circumstances,16,21
thereby limiting
the global use of E : Ea as an index of LVFP and CHF.
In contrast, a close linear relationship between mean left
atrial pressure and E : Ea (r 5 0.83, P o .05) was
reported from studies17
using a dog model of acute LV
volume overload secondary to severe iatrogenic mitral
regurgitation. In another study44
involving 39 dogs with
naturally acquired MVD, a correlation between E : Ea
and class of heart failure was documented. Using a
cut-off of 13.0, E : Ea identified CHF with a sensitivity
of 0.80 and a specificity of 0.83, which is similarly
low compared with our findings. Conflicting results
on the use of E : Ea as a reliable index of congestion
and increased filling pressures have been reported in
people with primary mitral valve regurgitation, with
most studies rejecting the use of E : Ea under such
circumstances.43,46
In contrast to DCM, the preload de-
pendency of Ea in hearts with preserved systolic function
and normal to only mildly affected diastolic function in
concert with disproportionate volume overload may
limit the use of E : Ea in the prediction of CHF in dogs
with MVD.20,43,45,46
Diagnosis of CHF by Doppler Transmitral Flow
Patterns and Class of Diastolic Function
The mitral inflow velocity profile is determined in a
complex manner by multiple factors, which include left
atrial pressure, relaxation, LV systolic pressure, ventric-
ular suction, preload, heart rate, and atrial function.47
The pattern of LV filling determined by Doppler trans-
mitral flow is used to noninvasively evaluate LV diastolic
performance and has been described in detail in peo-
ple22,41
and validated in experimental dogs.13,14,47
Early
stages of LV dysfunction most often seen in asymptom-
atic dogs with heart disease (or healthy dogs older than
10 years)33
commonly lead to a delayed relaxation trans-
mitral flow pattern.14,22,48
At this stage, LV relaxation is
prolonged but filling pressure still normal or only mini-
mally increased.48
With advancement of disease, LVFP
rises and overrides the relaxation abnormality dominant
influence on LV filling, leading to a renormalized (yet
‘‘pseudonormal’’) flow pattern.14,49
The final stage in the
natural history of LV diastolic dysfunction is restrictive
filling, a flow pattern indicating markedly increased
LVFP, most commonly associated with CHF.49
From a
clinical perspective it is of utmost importance to distin-
guish normal from pseudonormal flow for which
variables such as Aduration : ARduration or E : Ea may
be instrumental.22,41
The results of the present study
proved the clinical usefulness of assessing LV diastolic
function in the DE diagnosis of CHF in dogs with MVD
or DCM. Diastolic Functional Class, in particular re-
strictive filling, was highly predictive of CHF status.
However, it also became obvious that because of differ-
ences in disease characteristics, LV filling patterns in
dogs with DCM and MVD need different clinical deci-
sion-making cut-offs and require differential
interpretation. Whereas all dogs with preclinical DCM
had DE evidence of normal LV diastolic function or de-
layed LV relaxation and all dogs with symptomatic
DCM had restrictive LV filling, the situation was less de-
finitive in dogs with MVD. Owing to the fundamental
structural and functional differences between MVD and
DCM it is unlikely that a universal approach to both
conditions can be advanced with regard to interpretation
of DE variables. In DCM, there is primarily a systolic
dysfunction-dominant influence on LV filling and LV
stiffness is increased.1
Early work done in experimental
dogs and people revealed that the diagnostic ability to
assess LV diastolic function using transmitral flow pat-
terns is best when ejection fraction is reduced.13,22
This
was confirmed in our study in which 9 DE variables had
an AUC of 0.90 indicating excellent diagnostic perfor-
mance in the diagnosis of CHF in dogs with DCM. In
contrast, the volume-overload dominant influence on LV
filling combined with often normal global LV systolic
function, chamber compliance, and relaxation limits the
value of transmitral flow patterns in the diagnosis of
CHF in the setting of MVD.21,22,42
Pseudonormal and
even restrictive LV filling can both be the sole conse-
quence of volume overload.21
True restrictive filling is
characterized by markedly increased E : A, a very short
DTE, and a reduced Peak Ea.21,49
However, if E : A is
Table 5. Intra- and interobserver measurement vari-
ability of 18 echocardiographic variables assessed in 8
randomly selected dogs.
Intraobserver Interobserver
CV (%) Absolute CV (%) Absolute
LADs (cm) 1.41 0.07 1.41 0.06
Ao (cm) 2.50 0.04 4.32 0.08
LADs : Ao 3.53 0.10 4.00 0.11
IVRT (ms) 4.28 2.33 7.20 4.00
Peak E (m/s) 0.48 0.01 3.44 0.03
DTE (ms) 5.21 5.19 11.04 10.75
Peak A (m/s) 1.36 0.01 1.84 0.01
E : A 1.93 0.04 3.92 0.07
E : IVRT 4.64 0.10 10.45 0.22
Aduration (ms) 3.41 3.16 5.61 5.25
ARduration (ms) 3.47 3.05 6.24 5.50
Aduration : ARduration 5.13 0.05 9.10 0.10
Vp (cm/s) 5.60 2.15 3.78 1.41
E : Vp 5.06 0.13 5.06 0.14
Ea Sept (cm/s) 2.25 0.22 4.58 0.45
E : Ea Sept 3.36 0.40 3.18 0.38
Ea Lat (cm/s) 1.21 0.12 2.32 0.23
E : Ea Lat 1.59 0.18 2.26 0.26
CV, coefficient of variation.
See Table 2 for key.
1365
Congestive Heart Failure in Dogs

9. increased but DTE is only mildly reduced and Peak Ea is
normal or even increased, the effect of volume (ventric-
ular ‘‘overfilling’’), and not pressure, is considered the
main mechanism in the generation of the filling pattern
termed ‘‘pseudorestrictive.’’21
Therefore, the diagnosis of
CHF for an individual dog with MVD requires a step-
wise approach incorporating all available data, and
caution is advised in the isolated use of transmitral flow
patterns for such purpose.21,42,43,46,49
Diagnosis of CHF Using Natriuretic Peptides
Circulating natriuretic peptides are increased in dogs
with CHF because of MVD4,5,7,10,12
and DCM4,9–12
; and
dogs with CHF have higher blood concentrations than
dogs with preclinical disease.4,5,8–11
Results of the present
study indicate that (a) NT-proANP concentrations in
dogs with decompensated MVD were significantly (P o
.05) higher than in dogs with decompensated DCM de-
spite similar concentrations in dogs with preclinical
MVD or DCM; (b) NT-proBNP concentrations in dogs
with preclinical and decompensated DCM were signifi-
cantly (P o .05) higher than in dogs with preclinical and
decompensated MVD; (c) both NT-proANP and NT-
proBNP can be used in the prediction of CHF in dogs
with MVD although a clinically important overlap be-
tween dogs with preclinical and decompensated disease
was found; (d) only NT-proBNP but not NT-proANP
can be used in the prediction of CHF in dogs with DCM;
and (e) both natriuretic peptides have less accuracy in the
prediction of CHF as compared with many DE variables
and respiration rate. Our findings with regard to differ-
ences in natriuretic peptide concentrations between
compensated and decompensated dogs are similar to
findings from a recent studies in 156 dogs with MVD5,8
and 15 dogs with DCM11
but dissimilar, at least in part,
from findings in 20 Doberman Pinschers with DCM9
and
137 dogs with MVD or DCM.4
The identification of rea-
sons for such discrepancies was beyond the scope of the
present study but may indicate that more research is
needed to fully appreciate the clinical usefulness and po-
tential incremental value of natriuretic peptide analysis
in the diagnosis and management of patients with MVD
and DCM.
Diagnosis of CHF Using Respiration Rate
Respiration rate and the pattern of ventilation have a
long-standing clinical basis for identification of CHF.
However, effects of CHF on respiration rate have not yet
been prospectively studied in dogs to our knowledge.
Respiration rate is controlled by involuntary and volun-
tary mechanisms and, among others, correlates closely to
the amount of lung water.r,2
In the present study, respi-
ration rate taken at the hospital outperformed most DE
and laboratory variables in the diagnosis of CHF. A di-
agnostic cut-off of 41 and 34 per minute in dogs with
MVD and DCM, respectively, was useful in the predic-
tion of presence or absence of CHF with high accuracy
(sensitivity and specificity between 92 and 100%). These
results are very encouraging as respiration rate is very
simple to obtain, does not add additional costs, and can
be done repeatedly by instructed owners in the home
environment. The clinical relevance of this finding is
several-fold: determination of respiration rate might be
beneficial in the early diagnosis of CHF in dogs with
MVD and DCM; it might allow for earlier therapeutic
intervention; it could be a very cost-effective tool in the
assessment of success of treatment of CHF; and it might
allow both clinicians and owners to more accurately tai-
lor home treatment to a target RR and to avoid excessive
or insufficient diuresis. Although unproven, respiration
rate might also be useful in the discrimination on respi-
ratory distress because of either CHF or primary
respiratory disease. This study suggests that veterinari-
ans should use respiration rate in the diagnosis of CHF
and instruct owners to monitor RR in dogs with MVD
and DCM at risk for developing CHF.
Limitations
Certain weaknesses of this study need emphasis. One
limitation is the use of thoracic radiography in the diag-
nosis of CHF because of its limited diagnostic accuracy,
owing to a multitude of factors.6,7,25
Pulmonary capillary
wedge pressure, a surrogate measure of left atrial pres-
sure and thus filling pressure,50
was not measured in our
dogs. Therefore, the presence or absence of increased
LVFP could only be assumed on clinical and radio-
graphic ground and a quantitative relationship between
LVFP and echocardiographic and biochemical variables
could not be determined. Furthermore, because of the
mode of selection of dogs, pretest probability of CHF in
symptomatic dogs was high, limiting the more global ap-
plicability of the results of this study to all dogs with
clinical signs of CHF. Dogs with CHF were sedated,
which may have influenced central hemodynamics and
thus DE variables. The number of dogs studied was
small, in particular dogs with DCM, rendering the study
underpowered to detect differences among groups.
Moreover, echocardiography and blood sampling were
done only once in each dog, neglecting day-to-day and
circadian rhythms of filling pressure and circulating nat-
riuretic peptide concentrations.51,52
In addition,
variables and cut-offs used for classification of LV dia-
stolic function were chosen based on recommended flow
patterns for use in people41
and data obtained from a
prior pilot studym
in dogs with MVD and DCM. Age,
body weight, and heart rate were not specifically consid-
ered for diastolic classification and determination of
discrimination limits, although such variables may influ-
ence LV diastolic function.33
Sample handlingq
including
short-term (
o4 weeks) storage at 801C might have
affected analysis for natriuretic peptides. Finally, prior
treatment, in particular administration of furosemide,
could have confounded interpretation of DE and radio-
graphic findings.
Conclusions
Despite these limitations, the clinical implications of
our findings are that in dogs with CHF because of de-
generative MVD and DCM, E : IVRT, Diastolic
Functional Class, and IVRT are the Doppler indices best
1366 Schober et al

10. predicting presence of left-sided CHF but requiring
disease-specific discrimination limits for clinical use.
Respiration rate has a comparably high predictive
power, is simple to obtain, but needs further study to
fully appreciate its diagnostic value. Whether goal-
directed transthoracic DE focusing on evaluation of fill-
ing variables and CHF can be used to guide in the
management of patients with MVD and DCM remains
to be determined. If useful under such circumstances,
E : IVRT, Diastolic Functional Class, IVRT, and respi-
ration rate may become simple to perform invaluable
diagnostic studies for assessing CHF status and optimiz-
ing preload in dogs with left-sided CHF.
Footnotes
a
Ultrasonic Doppler flow detector, Model 811-B, Parks Medical
Electronics Inc, Aloha, OR
b
Sedecal, Sedecal USA, Arlington Heights, IL
c
Prestige II, GE Medical Systems, Milwaukee, WI
d
Digital radiography system EDR-6, Sound-Eklin, Carlsbad, CA
e
Viewing software E-film, Merge Healthcare, Milwaukee, WI
f
Vivid 7 Vantage with EchoPac software package version BT05,
GE Medical Systems
g
Acepromazine maleate injection, Boehringer Ingelheim Vetmed-
ica Inc, St Joseph, MO
h
Butorphenol injection, IVX Animal Health Inc, St Joseph, MO
i
Diana A, Sanacore A, Guglielmini C, et al. Radiographic features
of pulmonary edema associated with mitral regurgitation in dogs.
Vet Radiol Ultrasound 2008;49:213 (abstract)
j
IDEXX Laboratories, Westbrook, MA
k
VetSign Canine CardioSCREEN proANP, IDEXX Laboratories
l
VetSign Canine CardioSCREEN NT-proBNP, IDEXX Laboratories
m
Schober KE, Bonagura JD. Doppler echocardiographic assess-
ment of the E : Ea ratio as an indicator of left ventricular filling
pressure in normal dogs and dogs with heart disease. J Vet Intern
Med 2005;931 (abstract)
n
Sigma Stat, Version 3.5, SPSS Inc, Chicago, IL
o
Prism 4, Graph Pad Software Inc, San Diego, CA
p
SPSS Statistics version 9.2, SPSS Inc
q
Farace G, Beardow A, Carpenter C, et al. Effect of shipping tem-
perature on canine N-terminal pro-hormone atrial natriuretic
peptide and N-terminal pro-hormone brain natriuretic peptide.
J Vet Intern Med 2008;22:756 (abstract)
r
DaCunha DNQ, Pedraza A, Kuenzler R, et al. Trends in respira-
tion rate as an indicator of worsening heart failure. J Card Fail
2007;13 (Suppl 2): S173 (abstract)
Acknowledgments
The authors gratefully acknowledge Kathryn Meurs,
John Mattoon, Nicole Ponzio, Laura Spayd, Agnieszka
Kent, Patty Mueller, Becky Conners, and Richard Cober
for their contributions.
This study was supported by a grant from the Morris
Animal Foundation.
References
1. Lord PF. Left ventricular diastolic stiffness in dogs with
congestive cardiomyopathy and volume overload. Am J Vet Res
1976;37:953–957.
2. Guyton AC, Lindsey AW. Effect of elevated left atrial
pressure and decreased plasma protein concentration on the devel-
opment of pulmonary edema in dogs. Circ Res 1959;1:649–657.
3. Serres F, Chetboul V, Tissier R, et al. Chordae tendineae
rupture in dogs with degenerative mitral valve disease: Prevalence,
survival, and prognostic factors (114 cases, 2001–2006). J Vet Intern
Med 2007;21:258–264.
4. Oyama MA, Fox PR, Rush JE, et al. Clinical utility of
serum N-terminal pro-B-type natriuretic peptide concentration
for identifying cardiac disease in dogs and assessing disease sever-
ity. J Am Vet Med Assoc 2008;232:1496–1503.
5. MacDonald KA, Kittleson MD, Munro C, et al. Brain
natriuretic peptide concentration in dogs with heart disease and
congestive heart failure. J Vet Intern Med 2003;17:172–177.
6. Balbarini A, Limbruno U, Bertoli D, et al. Evaluation of
pulmonary vascular pressures in cardiac patients: The role of the
chest roentgenogram. J Thorac Imaging 1991;6:62–68.
7. Hansson K, Häggström J, Kvart C, et al. Reader perfor-
mance in radiographic diagnosis of signs of mitral regurgitation in
Cavalier King Charles Spaniels. J Small Anim Pract 2009;50(Suppl
1):44–53.
8. Tarnow I, Olsen LH, Kvart C, et al. Predictive value of
natriuretic peptides in dogs with mitral valve disease. Vet
J 2009;180:195–201.
9. O’Sullivan ML, O’Grady MR, Minors LS. Plasma big
endothelin-1, atrial natriuretic peptide, aldosterone, and norepi-
nephrine concentrations in normal Doberman Pinschers and
Doberman Pinschers with dilated cardiomyopathy. J Vet Intern
Med 2007;21:92–99.
10. Asano K, Masuda K, Okumura M, et al. Plasma atrial and
brain natriuretic peptide levels in dogs with congestive heart failure.
J Vet Med Sci 1999;6:523–529.
11. Tidholm A, Haeggstroem J, Hansson K. Effects of dilated
cardiomyopathy on renin-angiotensin-aldosterone system,
atrial natriuretic peptide activity, and thyroid hormone concentra-
tions in dogs. Am J Vet Res 2001;62:961–967.
12. Fine DM, DeClue AE, Reinero CR. Evaluation of circulat-
ing amino terminal-pro-B-type natriuretic peptide concentration
in dogs with respiratory distress attributable to congestive heart
failure or primary pulmonary disease. J Am Vet Med Assoc
2008;232:1674–1679.
13. Ohno M, Cheng CP, Little WC. Mechanism of altered
patterns of left ventricular filling during the development of
congestive heart failure. Circulation 1994;89:2241–2250.
14. Myreng Y, Smiseth OA. Assessment of left ventricular relax-
ation by Doppler echocardiography. Comparison of isovolumic
relaxation time and transmitral flow velocities with time constant
of isovolumic relaxation. Circulation 1990;81:260–266.
15. Schober KE, Stern J, DaCunha D, et al. Estimation of left
ventricular filling pressure by Doppler echocardiography in dogs
with pacing-induced heart failure. J Vet Intern Med 2008;22:
578–585.
16. Schober KE, Bonagura JD, Scansen BA, et al. Estimation of
left ventricular filling pressure by use of Doppler echocardiography
in healthy anesthetized dogs subjected to acute volume loading. Am
J Vet Res 2008;69:1034–1049.
17. Oyama MA, Sisson DD, Bulmer BJ, Constable PD.
Echocardiographic estimation of mean left atrial pressure in a
canine model of acute mitral valve insufficiency. J Vet Intern
Med 2004;18:667–672.
18. Nagueh SF, Middleton KJ, Kopelen HA, et al. Doppler
tissue imaging: A noninvasive technique for evaluation of left
ventricular relaxation and estimation of filling pressures. J Am
Coll Cardiol 1997;15:1527–1533.
19. Feissel M, Maizel J, Robles G, et al. Clinical relevance
of echocardiography in acute severe dyspnea. J Am Soc Echo-
cardiogr 2009;22:1159–1164.
1367
Congestive Heart Failure in Dogs

11. 20. Jacques DC, Pinsky MR, Severyn D, et al. Influence of
alterations in loading on mitral annular velocity by tissue Doppler
echocardiography and its associated ability to predict filling
pressures. Chest 2004;126:1910–1918.
21. Masutani S, Little WC, Hasegawa H, et al. Restrictive
left ventricular filling pattern does not result from increased left
atrial pressure alone. Circulation 2008;117:1550–1554.
22. Appleton CP, Firstenberg MS, Garcia MJ, et al. The
echo-Doppler evaluation of left ventricular diastolic function. A
current perspective. Cardiol Clin 2000;18:513–546.
23. Beardow AW, Buchanan JW. Chronic mitral valve disease in
Cavalier King Charles Spaniels: 95 cases (1987–1991). J Am Vet
Med Assoc 1993;203:1023–1029.
24. Dukes-McEwan J, Borgarelli M, Tidholm A, et al. Proposed
guidelines for the diagnosis of canine dilated cardiomyopathy. J Vet
Cardiol 2003;5:7–19.
25. Staub CN, Nagano H, Pearce ML. Pulmonary edema in
dogs, especially the sequence of fluid accumulation in lungs. J Appl
Physiol 1967;22:227–240.
26. Boswood A, Attree S, Page K. Clinical validation of a
proANP 31-67 fragment ELISA in the diagnosis of heart failure in
the dog. J Small Anim Pract 2003;44:104–108.
27. Rishniw M, Erb HN. Evaluation of four 2-dimensional
echocardiographic methods of assessing left atrial size in dogs.
J Vet Intern Med 2000;14:429–435.
28. Schober KE, Luis Fuentes V, Dukes McEwan J, et al. Pul-
monary venous flow characteristics as assessed by transthoracic
pulsed Doppler echocardiography in normal dogs. Vet Rad Ultra-
sound 1998;39:33–41.
29. Garcia M, Smedira NG, Greenberg NL, et al. Color M-
mode Doppler flow propagation velocity is a preload insensitive in-
dex of left ventricular relaxation: Animal and human validation.
J Am Coll Cardiol 2000;35:201–208.
30. Nadrous HF, Pellikka PA, Krowka MJ, et al. Pulmonary
hypertension in patients with idiopathic pulmonary fibrosis. Chest
2005;128:2393–2399.
31. Schober KE, Baade H. Doppler echocardiographic predic-
tion of pulmonary hypertension in West Highland White Terriers
with chronic pulmonary disease. J Vet Intern Med 2006;20:912–920.
32. Schober KE. Echocardiographic assessment of left ventricu-
lar filling pressure—fact or fiction? 26 Annual Meeting of
Veterinary Medical Forum, San Antonio, TX, June 4–7, 2008.
33. Schober KE, Luis Fuentes V. Effect of age, body weight, and
heart rate on transmitral and pulmonary venous flow in clinically
normal dogs. Am J Vet Res 2001;62:1447–1454.
34. Taube A. Sensitivity, specificity, and predictive values: A
graphical approach. Stat Med 1986;5:585–591.
35. McNemar M, Quinn B. Note on the sampling error of the
difference between correlated proportions or percentages. Psycho-
metrika 1947;12:153–157.
36. Krampe A, Kuhnt S. Bowker’s test for symmetry and mod-
ifications within the algebraic framework. Comp Stat Data Anal
2007;51:4124–4142.
37. Martin SW, Meek AH, Willeberg P, eds. Veterinary
Epidemiology, Principles and Methods. Ames, IA: Iowa State Uni-
versity Press; 1987:73–76.
38. Shrout PE, Fleiss JL. Intraclass correlations: Uses in assess-
ing rater reliability. Psychol Bull 1979;2:420–428.
39. Atkinson G, Nevill AM. Statistical methods for assessing
measurement error (reliability) in variables relevant to sports med-
icine. Sports Med 1998;26:217–238.
40. Garcia MJ, Ares MA, Asher C, et al. An index of early left
ventricular filling that combined with pulsed Doppler peak E veloc-
ity may estimate capillary wedge pressure. J Am Coll Cardiol
1997;29:448–454.
41. Appleton CP, Hatle LK, Popp RL. Relation of transmitral
flow velocity patterns to left ventricular diastolic function: New in-
sights from a combined hemodynamic and Doppler
echocardiographic study. J Am Coll Cardiol 1988;12:426–440.
42. Diwan A, McCulloch M, Lawrie GM, et al. Doppler estima-
tion of left ventricular filling pressures in patients with mitral valve
disease. Circulation 2005;111:3281–3289.
43. Olson JJ, Costa SP, Young CE, et al. Early mitral filling/di-
astolic mitral annular velocity ratio is not a reliable predictor of left
ventricular filling pressure in the setting of severe mitral regurgita-
tion. J Am Soc Echocardiogr 2006;19:83–87.
44. Teshima K, Asano K, Sasaki Y, et al. Assessment of left ven-
tricular function using pulsed tissue Doppler imaging in healthy
dogs and dogs with spontaneous mitral regurgitation. J Vet Med
2005;67:1207–1215.
45. Opdahl A, Remme EW, Helle-Valle T, et al. Determinants of
left-ventricular early-diastolic lengthening velocity: Independent
contributions from left ventricular relaxation, restoring force, and
lengthening load. Circulation 2009;119:2578–2586.
46. Bruch C, Stypmann J, Gradaus R, et al. Usefulness of tissue
Doppler imaging for estimation of filling pressures in patients with
primary and secondary pure mitral regurgitation. Am J Cardiol
2004;93:324–328.
47. Choong CY, Abascal VM, Thomas JD, et al. Combined in-
fluence of ventricular loading and relaxation on the transmitral flow
velocity profile in dogs measured by Doppler echocardiography.
Circulation 1988;78:672–683.
48. Rihal CS, Nishimura RA, Hatle LK, et al. Systolic and dia-
stolic dysfunction in patients with clinical diagnosis of dilated
cardiomyopathy. Circulation 1994;90:2772–2779.
49. Whalley GA, Doughty RN, Gamble GD, et al. Pseudonor-
mal mitral filling pattern predicts hospital re-admission in patients
with congestive heart failure. J Am Coll Cardiol 2002;39:1787–1795.
50. Chaliki HP, Hurrell DG, Nishimura RA, et al. Pulmonary
venous pressure: Relationship to pulmonary artery, pulmonary
wedge, and left atrial pressure in normal, lightly sedated dogs. Cath-
eter Cardiovasc Interv 2002;56:432–438.
51. Ishikawa T, Tanaka R, Suzuki S, et al. Daily rhythms of left
atrial pressure in Beagle dogs with mitral valve regurgitation. J Vet
Intern Med 2009;23:824–831.
52. Kellihan HB, Oyama MA, Reynolds CA, et al. Weekly vari-
ability of plasma and serum NT-proBNP measurements in normal
dogs. J Vet Cardiol 2009;11:93–97.
Appendix 1. Radiographic composite score on conges-
tive heart failure (CHF).
Variable Assessment Points
Left atrial enlargement None 0
Mild 1
Moderate to severe 3
Pulmonary venous
congestion
None 0
Present 3
Pulmonary infiltrates
compatible with
cardiogenic edema
None 0
Mild interstitial 1
Diffuse interstitial 2
Alveolar 3
Pleural effusion None 0
Yes 1
Final assessment Score 0–2 CHF not likely
Score 3–4 CHF possible
Score 44 CHF likely
1368 Schober et al