Exercise Training Effect in Chronic Heart Failure
ABSTRACT & COMMENTARY
Synopsis: Exercise training reduces peripheral resistance and cardiomegaly and improves stroke volume in chronic stable heart failure patients.
Source: Hambrecht R, et al. JAMA 2000;283:3095-3101.
Hambrecht and associates took 36 men, average age of 55 years with chronic heart failure (left ventricular ejection fractions < 27%) and randomly assigned them to six months of bicycle exercise training for 20 minutes a day at a precalculated 70% of their peak oxygen uptake. The no-intervention group was known as the control group. These 37 patients had no specific exercise assigned to them. Baseline characteristics were equivalent on both sides of the study. A total of 73 started, and 64 patients completed the whole six-month study. Approximately equal numbers were excluded on either side. By performing right heart catheterization and ascertaining stroke volume, left ventricular ejection fraction and other cardiac data prior to the study and then repeating at six months, they were able to show with statistical significance an improvement in the New York Heart Association functional class in the exercise group. They documented it with improved exercise capacity and maximum oxygen uptake parameters. When tweezing the data, they found that total peripheral resistance was reduced in the exercise patients but was raised in the control patients. Hambrecht et al concluded that this aerobic exercise training increased left ventricular stroke volume both at rest and at exercise while keeping cardiac output unchanged. Long-term, the exercise training of this study reduced the total peripheral resistance. This may actually have effects on endothelial dependent vasodilation of the skeletal muscle vasculature. They also stated that the total peripheral resistance and stroke volume in left ventricular end-diastolic diameter changes result in a significant after load reduction.
COMMENT BY LEN SCARPINATO, DO, FACP, FCCP
Like you, as a primary care clinician, I have had the experience of heart failure patients being told not to exercise because it might cause a cardiac decompensation. As a health-fitness advocate, this always concerned me.
Over the last 10 years, it has been noticed that this approach to heart failure patients may actually decondition them and worsen their heart failure symptomatology over time. The emergence of cardiac rehab programs, which increased the work capacity in patients with chronic heart failure, has changed this perception. Research studies have shown an increase in the oxidative capacity of the skeletal muscle and corrections in endothelial dysfunction. Interestingly, actual studies of important cardiac parameters studied by Hambrecht et al were not done previously.
The significance of this study is that they looked at six months of exercise in a heart failure population. Although not designed to describe how many patients lived or died, there was roughly comparable equivalence of the number of deaths on both sides (3 in the intervention group, 2 in the control group) as well as those who withdrew or were excluded (2 each). The highly specific testing that was done on these patients and the rather rigorous statistical analysis proved to me that there is indeed an effect of exercise on the heart more than just on the skeletal muscle.
Hambrecht et al’s study had a significant number of ace inhibitor patients but not as many beta blocker patients. These real changes in total peripheral resistance are like initiation of an ace inhibitor or a beta blocker in patients. Thus, it can be surmised that this effect on afterload reduction is in addition to that provided by medication and, therefore, would also potentially improve outcome.
Being an "in the trenches" clinician, I am primarily concerned about patient’s New York heart classification in heart failure. When the ace inhibitor captopril was trying to become the standard of care in heart failure, studies were done comparing it to digoxin. I was impressed at that time with the improvement in New York heart classification that ace inhibitors provided compared to the lack of that with digoxin, in a statistically significant way. We now have the study that shows that exercise can do the same thing.
You can be sure that I will continue to promote exercise in my heart failure patients. Now I will be able to point to a specific study that shows it is like taking additional medication and it can improve some specific parameters.
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