Direct visualization of coronary arteries using transthoracic echocardiography

1. Transthoracic Echocardiography in the
Assessment of Coronary Arteries
Dr. Samir M. Yousif

2. Introduction
Quantitative coronary angiography remains
the reference standard for assessing
coronary anatomy, measuring anatomic
severity of the stenotic lesion and assisting
in the process of intracoronary
interventions

3. however
severity correlates better with physiologic disturbances
which can be revealed by the analysis of coronary
artery flow and coronary flow reserve (CFR)

5. methods of studying coronary hemodynamics
• Doppler flow wires and catheters
• positron emission tomography
• transesophageal echocardiography
limitations:
• semi-invasive
• proximal LAD (69% to 97%)
• RCA (66% to 83%)
transstenotic or prestenotic CFR but not poststenotic CFR

6. transthoracic echocardiography (TTE) evaluation of the CAD
How coronary arteries should be visualized by TTE ?
One of the first reports on TTE visualization of distal
LAD as a vessel with a most superficial location (3-7 cm
from skin) was presented by Fusejima et al., 1987.(35%
control ,50 cardiac disease)

7. • assessment of regional and global left
ventricular function
• in children and occasionally in adults
coronary artery anomalies, arteriovenous
fistulas and aneurysms

8. BUT Now WITH
• advent of harmonic imaging, contrast
agents high-frequency transducers
direct transthoracic Doppler visualization of
non-dilated arteries and measurement of
coronary artery flow is now relevant in the
majority of patients

9. • improvement by contrast agents (levovist) from 40
% to 80% in mid-distal LAD ,from 30 % to 86 % in
PDA , for CFR in LAD from 70% to 97% .
• High frequency transducers for distal LAD or PDA
• multifrequency (1.7- to 3.5-MHz) transducer with
second tissue harmonics

10. optimization of ultrasound images
• the sample size of color Doppler
should be kept at minimum
• low Nyquist limit (15-20 cm/s),
• filters should be decreased

11. windows of examination
• parasternal short- and long-axis views from second-
or third intercostal space , parasternal short- or long-
axis views from fourth- or fifth intercostal space
• a modified apical 2, 3 or 5-chamber view or subcostal

12. coronary arteries appear as linear intramyocardial color
fragmental structures of approximately 0.5-2.5 cm in
length and 2 to 4 mm in diameter

16. Visualisation of the left anterior descending coronary
artery
parasternal short axis view of the great vessels
Slight change of the imaging plane so that it traverses the
heart immediately below the pulmonary trunk allows for
visualization of the left main (LM) and proximal LAD

20. Depending on anatomical relations
in a particular patient, sometimes it is easier to assess
the proximal part of the LAD in a modified parasternal long
axis views The artery may be seen there as it traverses
below the pulmonary trunk towards the interventricular
groove

21. The LM and proximal LAD may also be
viewed using a modified apical five chamber view

22. The middle and distal LAD may be assessed by placing
the transducer in low parasternal position
The interventricular groove is located in short axis view and
then the transducer is either tilted towards the base of the
heart or rotated to obtain a modified long axis view

23. The middle and distal
LAD can also be visualized using a modified apical 5-
chamber view (traversing anterior wall of the heart). The
entire LAD together with some diagonal branches can
sometimes be assessed in this view

24. Apical window is usually the best to obtain low
Doppler angles for velocity measurements in
the LAD
The transducer is moved to the subcostal location
and a long axis view of the heart is obtained Then
the transducer is tilted anteriorly to get the anterior
wall of the left ventricle where long segments of
the LAD can be visualized

25. Visualisation of the left circumflex coronary artery
The Cx is visualized in parasternal short axis
view with imaging plane traversing the heart
immediately below the pulmonary trunk

27. Sometimes it is better seen when the probe is
directed just below the left atrial appendage

28. To visualize the middle Cx at the border between
the atrium and the ventricle especially with the
imaging plane traversing the mitral annulus

29. sometimes it is easier to assess the proximal and
middle Cx in a modified parasternal long axis views.

30. The transducer may then be moved to the
apex and a modified five chamber view
(traversing anterior wall of the heart),Area
lateral to the sinus of Valsalva is carefully
searched A reliable measurement of the
flow velocity within the initial part of the
Cx may then be performed

31. Visualisation of the right coronary artery
The parasternal short axis plane may be
used to visualize the proximal RCA . It may
be relatively easily visualized
in B-mode ,while Doppler examination is
usually required to locate its middle and
distal parts

33. sometimes it is easier to assess the proximal RCA
in a modified parasternal long axis views. The
proximal RCA may be seen in this view running
along the anterior wall of the aorta

34. The proximal RCA can infrequently
be visualized using apical window, but this view
allows for recording of the flow velocity pectrum

35. The middle RCA is visualized in subcostal view
and the anterior wall of right ventricle at the
coronary sulcus is carefully scanned

37. The distal RCA can be assessed using apical 4
chamber view then the transducer is tilted more
perpendicular to the chest so that the imaging plane
traverses the inferior wall of the heart and the posterior
interventricular groove. Alternatively, a modified 2-
chamber view (crossing the heart along the posterior
interventricular groove) can be used

39. Main pitfalls
• confusion with Certain large branches of coronary
arteries – the intermediate coronary artery, diagonal and
marginal branches
• distinction between various vessels seen at the lateral
and inferior walls of the ventricle
• certain extra cardiac arteries
• assessing the place of coronary stenosis
• distinction between coronary artery and concomitant
vein
• pericardial fluid

40. Success rate of the detection of main coronary
arteries by TTE
• TTE demonstrated adequate success
rate of color Doppler mapping of
the LMCA, all LAD segments and PDA,
and poor feasibility in detecting other
segments of main coronary arteries

42. Normal Doppler systole-diastolic coronary flow pattern in coronary
arteries
• Doppler image is presented as continuous, biphasic
systole-diastolic flow with predominant diastolic
phase and low velocities.
• Normal Doppler coronary flow velocities at rest
highly reproducible and correlate with PET

43. measurements can include
• peak velocity
• time velocity integral
• mean velocity in systole and diastole
• duration of diastolic and systolic flow

44. the peak diastolic velocity in distal LAD was
average 21 cm/s and the duration of diastolic
coronary artery flow was average 58% of the R-R
interval at rest within the range of physiologic
heart rates (60-100 b/m)

47. Detection of coronary artery stenosis and occlusion by
TTE at rest
• Unlike computed tomography, TTE as well as
coronary angiography detects coronary stenosis
basing not on visualizing atherosclerotic plaque per
se but revealing stenosis of coronary artery lumen in
the site of the plaque.i.e primarily the function of
coronary vessels by detecting stenosis as focal zones
with acceleration and turbulence of coronary blood
flow.

48. Direct detection of atherosclerotic plaques and
assessment of coronary artery wall thickness
reliable only in case of a major proximal plaque
with acoustic shadow due to calcium

50. intravascular ultrasound and epicardial echocardiography
studies have demonstrated that coronary atherosclerosis
is a diffuse pathological process and before CAD is clinical
evident, >90% of the coronary artery tree is therosclerotic

51. High-frequency TTE using a 7.5 or 10 MHz
transducer can be used to correctly and
accurately measure the wall thickness and
diameter of distal LAD and to detect their
changes

52. Takeuchi et al, 2006,demonstrated that wall
thickness and external diameter of the LAD
enlarged with the increase of the number of
CAD risk factors, and wall thickness of the LAD
>0.72 mm was a predictor of LAD stenosis with
74% sensitivity and 87% specificity

53. • TTE can detect vasodilating effects of nitroglycerin and
salbutamol on the LAD, correlating with peripheral
vascular reactivity to these vasodilators
• Focal aliasing and flow acceleration in the site of a
significant stenosis
• The peak diastolic velocity >1.5 m/s has demonstrated
85% sensitivity and 88% in the detection of LMCA
stenosis>50%

55. The ratio of stenotic to prestenotic blood flow velocity
• it has been found that the stenotic-to-prestenotic
peak blood flow velocity ratio over than 2.0 to be a
sign of >50% stenosis with 62-100% sensitivity and
92-100% specificity for the LAD, 63% sensitivity and
96% specificity for the RCA, and 38% sensitivity and
99% specificity for the Cx

57. stenosis, % = 100 * (1 - prestenotic
VTId / stenotic VTId)
• The sensitivity and specificity of >50%
stenosis identification by a modified
continuity equation in the LAD are
72% and 96%, in the Cx - 40% and
94%, and in the RCA – 50% and 93%

59. detection of coronary occlusion by TTE
• TTE does not seem to be a suitable method for the
assessment of acute coronary occlusions but is useful
after acute myocardial infarction for the detection of an
open LAD
• chronic total coronary occlusion (CTO) of over 1-month
duration leads to the formation of stable collateral
coronary pathways It has been established that
retrograde flow in distal LAD is a good marker of LAD
occlusion with 88% sensitivity and 100% specificity

60. TTE can answer the principal question – whether
the LAD or RCA is chronically opened or closed

62. Noninvasive assessment of coronary
flow reserve (CFR) in main coronary
• Reserve of coronary blood flow is defined
as the ability of coronary flow volume to
increase under maximal coronary
hyperemia when compared with coronary
flow volume at rest
• TTE can be used as a possible substitute of
the invasive method for correct clinical
measurement of CFVR, particularly in the
LAD

64. In one study, CFVR with a cut-off value <2.0
was a significantly better predictor
(90%sensitivity,96%specificity) of LAD
stenosis than multidetector computed
tomography (80%sensitivity,93%specificity

65. noninvasive CFVR assessment by TTE is a very
promising tool in monitoring early efficacy of LAD
angioplasty or stenting and detecting remote
restenosis after LAD intracoronary interventions

66. CFVR and prognosis in CAD patients
• In the study of Meimoun et al., 2009, a cut-off CFVR
value of 1.7 was an independent predictor of both
the left ventricle recovery at a 3-month follow-up,
and in-hospital adverse cardiac events including
death, recurrent myocardial infarction, and acute
heart failure

67. • CFVR provides independent information for
prognostic stratification, and a reduced CFVR is
associated with a less benign long-term
outcome in patients with acute anterior
myocardial infarction, known or suspected CAD
with positive and particularly negative stress
echocardiography by wall motion criteria. CFVR
measurement is offered to be added to routine
stress echocardiography

68. Conclusion
noninvasive clinical repeated or serial measurements
of coronary flow velocity at rest and after stress which
are necessary for understanding the physiology and
pathophysiology of coronary flow; in this case the LAD
can be used as a reference vessel

69. preliminary identification of coronary stenosis in the
LMCA, LAD and PDA;
- detection of restenosis after percutaneous
intracoronary interventions in the LMCA, LAD and
PDA;

70. diagnosis of reperfusion in the acute phase of
myocardial infarction in the LAD territory with
evaluation of no-reflow after recanalization
- identification of chronic occluded LAD and RCA
measurement of CFVR in different subsets of patients

71. THANK YOU