Stuart Russell, MD Duke University

1. Functional testing in
ambulatory heart failure:
What to test and how
often?
Stuart D. Russell, MD
Professor of Medicine

2. Disclosures
Research
NIH
Bodyport
Acorai
DSMB – Abbott

3. Outline
6 minute walk
Cardiopulmonary exercise testing
How developed
Predictor of prognosis
How I use

4. 6 minute walk
27 respiratory patients, 18 HF patients
Each did a total of 6 walks over 3 months
Some were encouraged, some weren’t
Can Med Assoc J 1985;132:919-23

5. How to perform
2 chairs separated by some distance – usually 20 to 30 meters
Flat corridor without distractions
One observer that gives routine, standardized encouragement
Call out the time every 2 minutes
Patients told to walk at a comfortable pace for as long as they can, feel
free to rest if necessary
Measure distance walked in 6 minutes

6. 6 minute walk
Can Med Assoc J 1985;132:919-23
HF encouraged
Resp encouraged
HF not encouraged
Resp not encouraged

7. Prognosis in SOLVD
0
2
4
6
8
10
12
Mortality
%
< 300 300-375 375-450 >450
Distance walked (m)
Bittner et al JAMA 1993;270:1702

8. ESCAPE Prognosis for Mortality - 6 minute walk
0.00
0.05
0.10
0.15
0.20
0.25
0.30
No test 1 to 300 301 to 600 Greater than 600
Six Minute Walk (Feet)
Mortality
(6
Month)
ACC 2005

9. 6 minute walk
Predicts outcomes in outpatients (HF-ACTION JACC 2012;60:2653)
Predicts risk of readmissions (Heart Lung 2017;46:287)
Predicts mortality outcomes after admissions (J Card Fail 2009;15:130)
41% if < 200 m, 19% if > 200 m at 40 months
(ft)

10. 6 min walk vs peak VO2
Lipkin et al Br Med J 1986;292:653

11. Limitations
Ingle et al (Eur J Heart Failure 2006;8:321)
571 pts with distance 337m
Poor walking distance correlates with …
Age > 75 (O.R. 4.0)
low BMI (O.R. 3.4)
anemia (O.R. 2.8)
HR > 80 (O.R. 2.2)
Female (O.R. 2.0)
ProBNP, self perceived feelings of depression and anxiety also
show dose-response effects
Similar findings in patients without structural heart disease

12. CPX testing

13. It used to be a lot more painful….
https://www.pftforum.com/history/gallery/the-douglas-bag/

14. Coupling of External to Cellular Respiration
Wasserman K. Exercise Gas Exchange in Heart Disease. Future 1996.
CO2 production O2 flow Expired
O2 consumption CO2 flow Inspired
Response: QO2 SV, HR VT, f
Ventilatory pump
Lung muscles
Myasthenia
Guillain-Barre
Chest wall
Kyphoscoliosis
Airways
Interstitial fibrosis
Emphysema
COPD
Cardiac
Heart failure
Pulm edema
Decrease flow
Drugs
Muscle
Muscle disease
Mitochondrial function
Other factors
Altitude
Anemia

15. VO2 max
Measures maximal reserve of the cardiovascular system
Directly related to cardiac output
Determines peak level of dynamic exercise
Physiologically meaningful
VO2 = cardiac output x (A-V) O2 difference
= HR x SV x (A-V) O2 difference
= HR x EDV-ESV
Determined by …
Type of exercise
Gender
Age
Activity level
Natural endowment
Drugs

16. 16
Clinically Meaningful Improvement for Patients
Correlates with an important increase in the ability to perform daily life
activities
0
10
20
30
40
50
60
70
80
90
100
4 6 8 10 12 14 16 18 20
Oxygen Uptake (ml/kg/min)
Daily
Activities
%
Bedridden
Bed to Chair
Homebound
Mobile with assistance
Independent
Active
Unrestricted
Modified from Jones N, 1988. Clinical Exercise Testing. Saunders.

17. Peak oxygen consumption and transplant
Prospective eval from 10/86 to 12/89
122 patients referred for transplant
All patients did a metabolic exercise test
Divided into three groups
1 - VO2 < 14 and listed for transplant
2 - VO2 > 14 and felt to be too well for transplant
3 - VO2 < 14, rejected for transplant for
noncardiac reasons
Mancini et al Circ 1991;83:778

18. Survival post Tx and medical Rx
Mancini et al Circ 1991;83:778

19. 1 Year Survival and Peak VO2
J Am Coll Cardiol 2016; 67:780.

20. Peak VO2 and prognosis
Complications after major surgery Ann Surg 2010;251:535
AT VO2 > 11.9 had fewer complications
Survival after liver transplant Liver Transpl 2012;18:152
AT VO2 < 9 had all but one die
Outcomes with hypertrophic CM Heart. 2016;102:602-9
Peak VO2 < 15.3 has 14% rate of death/OHT at 5 yrs
Outcomes after LVAD JACC HF 2021;9:758

21. Findings during CPX testing
Population VO2 Ve MVV DI Sx AT
Normal Nml Nml Nml <0.7 Fatigue Nml
Fit High High High >0.7 SOB High
Pulm limit Low Low Low >0.7 SOB Nml
Cardiac limit Low Low Low/Nml <0.7 SOB Low O2 pulse
Unfit Low Low Nml Nml <0.7 SOB Low OUES

22. ACC/AHA guidelines for exercise and functional capacity
testing 2022
JACC 2022;679:e263-e421
Assess prognosis
Why is my patient short of breath – heart or lungs or fitness or frailty or BMI
I don’t have a good feel for the true functional capacity of my patient
Lazy, under-reporter (what is the spouse saying?)
Assess pre-operative risk
Evaluate for disability
To determine intensity of exercise training in cardiac rehab