Wednesday, April 8, 2009

Should Patients with Heart Failure Receive Exercise Therapy? Implications for Disease Management Organizations with Heart Failure Programs

O’Conner and colleagues asked that question in an April 8 JAMA article titled “Efficacy and safety of exercise training in patients with chronic heart failure.’ You’d think exercise is good, because it increases stamina, promotes well being and should decrease the likelihood of the heart getting worse.

Maybe, maybe not.

The Disease Management Care Blog is going to share its four conclusions first. Readers who find them interesting may want to read the rest of this lengthy post. Even if you don’t want to read all of this, the conclusions alone should enable you to confidently quote from JAMA on an important issue in disease management - to the amazement of your colleagues and boss. That's because you regularly read the DMCB:

1. Among this ambulatory population with chronic heart failure, the overall event rate was striking: over the 30 months, there was a 15% mortality rate and about 2/3 ended up dying or being hospitalized. Chronic heart failure is a bad disease.

2. If a population of patients with a mean age of 59 years and on maximal medical therapy is assigned exercise, a simple assessment of utilization (hospitalizations, ER visits and the like) won’t show any impact. Your fees will be at risk.

3. This paper suggests baseline exercise tolerance, the level of heart function, mood, history of atrial rhythm problems and the cause of heart failure can have an impact on outcomes. Predictive modeling keying on these factors may be necessary to identify patients with a clinical profile that suggests exercise therapy is helpful. Good luck trying to convince your customers after the fact that these clinical factors helped or hindered your results. Adjusting for co-variates after the fact is a luxury for the academics, not you.

4. Even if the disease management organization does everything right in the promotion of exercise for persons with heart failure, the impact won’t be seen for about 2 years. A single year reconciliation may miss the impact of exercise in this population.

Recall ‘chronic heart failure’ typically describes a condition in which the heart muscle is weak and the heart chambers dilate. Interestingly, ‘forward’ (or downstream) flow (into the arteries of the body) is preserved. It’s ‘behind’ (or upstream) where the blood flow dams up. This leads to fluid retention (swollen legs) and shortness of breath (from fluid buildup in the lungs). Think of that sump pump downstairs: as that begins to fail, the hose leading outside still has lots of flow. It’s the basement that’s filling up with water.

This 82 site study randomized 2331 patients with weakened hearts to either 1) usual care with advice to exercise or 2) three supervised 15-35 minute group sessions of walking, treadmill or stationary cycling per week for a total of 36 sessions (over 3 months) aimed at getting to 70% of maximum heart rate. The duration was increased over the next 4-6 months and then slightly decreased with an ultimate target of continuing to exercise for a total of 120 minutes per week. The average age was 59 years, 40% were non-white and the median ejection fraction (a test of just how flabby the heart is) was 25% (compared to the normal measure of more than 50%, that’s low).

Key results?

All cause mortality 17% (usual care or EC) vs. 16% (exercise group or EG). Not statistically significantly different (NS).

All cause mortality or being hospitalized 68% (UC) vs. 65% (EG), not significant (NS).

All cause mortality or being hospitalized or having an emergency room visit or urgent clinic visit for heart failure problems 77% (UC) vs. 76% (EG), not significant (NS).

Cardiovascular mortality of hospitalization: 58% (UC) vs. 55% (EG), not significant (NS)

The Disease Management Care Blog was ready to conclude that heart failure exercise was destined for the comparative effectiveness research dumpster. Then it ran into this statement:

“Four baseline characteristics (duration of the… [baseline] exercise test, ventricular ejection fraction, Beck Depression… score and history of atrial fibrillation or flutter) were identified as highly prognostic. After adjusting for these covariates and heart failure etiology, exercise training was found to reduce the incidence of all-cause mortality or hospitalization by 11%.”

This 11% effect (by looking at the figures) was not readily apparent for about two years.

Huh? The DMCB recalls that this study involved randomization. That’s supposed to assure that all the conditions that might favor one group over the other are evenly distributed. If the baseline prevalence of exercise tolerance, heart function, mood, atrial rhythm disturbances and heart failure cause were the same in both groups (and it looks like they were), why would the authors make this statement?

The answer is because adjusting for covariates in randomized trials is not unusual . The ‘adjustment’ is a statistical approach that helps neutralize the persistent impact of these factors once the trial is concluded. As their impact was dampened, the difference in all cause mortality and hospitalization became more apparent.

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