Cardiac Rehabilitation
Clinical Significance of an Exercise Program After Cardiac Resynchronization Therapy
2022 Volume 86 Issue 1 Pages 58-59
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2022 Volume 86 Issue 1 Pages 58-59
The prevalence of heart failure (HF) in developed countries, including Japan, is approximately 1–2%, and this increases in older populations. HF is characterized by decreased exercise capacity attributable to neurocirculatory, vascular functional, and skeletal muscle factors. Cardiac resynchronization therapy (CRT) improves left ventricular ejection fraction (LVEF), exercise capacity, quality of life (QOL) scores,1,2 and prognosis3,4 in patients with HF and reduced LVEF (especially that associated with left bundle branch block). These benefits of CRT are due to an improvement in the central cardiovascular function of the heart (Figure). This improvement in cardiac function leads to reverse remodeling with a reduction in the size of the LV.4 However, previous reports have demonstrated a 30% non-responder rate in LVEF improvement.5 Participation in exercise-based cardiac rehabilitation after CRT reportedly improves patients’ peak V̇O2 and QOL,6–8 mainly via peripheral effects (Figure). Therefore, cardiac rehabilitation after CRT is recommended by the current HF practice guidelines at the Class I level.9–11 Important clinical questions are: (1) whether cardiac rehabilitation after CRT is beneficial for non-responders and (2) whether cardiac rehabilitation after CRT improves long-term prognosis.
Different effects of cardiac resynchronization therapy and exercise on advanced heart failure with reduced ejection fraction. Af, atrial fibrillation; EF, ejection fraction.
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In this issue of the Journal, Misumi et al12 first investigate the relationship between CRT response and response to exercise-based cardiac rehabilitation, as well as that between %∆LVEF after CRT and %∆ peak V̇O2 after exercise-based cardiac rehabilitation, in an observational study. The 3-month exercise-based cardiac rehabilitation program was initiated through supervised in-hospital sessions (5 days per week), followed by supervised outpatient sessions (1–3 times per week). The exercise program predominantly comprised aerobic exercises, such as walking, cycling on an ergometer, and calisthenics, as well as home exercise (90–150 min per week). The intensity of the aerobic exercise was determined individually using 1 of the following criteria: 40–50% of the actual measured heart rate reserve (Karvonen’s equation, k=0.4–0.5), heart rate at the anaerobic threshold determined during CPX, or the heart rate at level 12–13 (“somewhat hard”) on the Borg rating. They found that %∆ peak V̇O2 after exercise-based cardiac rehabilitation did not correlate with %∆LVEF after CRT, and that a good response to exercise-based cardiac rehabilitation could be expected even in poor CRT responders, especially those with sinus rhythm or low baseline peak V̇O2. These results suggest that the peak V̇O2 response to exercise-based cardiac rehabilitation and the LVEF response to CRT are independent, and that patients with severe HF undergoing CRT implantation can experience an improvement in their exercise capacity through exercise-based cardiac rehabilitation, regardless of the degree of improvement in LVEF after CRT. The peripheral effects of exercise and the cardiac effects of CRT may have synergistic or counteracting effects in patients with advanced HF with reduced EF (HFrEF). According to the most recent systematic review13 on the effect of exercise training in patients with chronic HF who underwent CRT, the maximal workload (mean difference [MD] 26.32 W, 95% confidence interval (CI) 19.41–33.23; P<0.00001, I2=0%) and exercise duration (MD 68.95 s, 95% CI 15.41–122.48; P=0.01, I2=76%) showed significant improvement in the exercise training group vs. control group (235 patients, 7 randomized controlled trials).
The Heart Failure: A Controlled Trial Investigating Outcomes of Exercise Training (HF-ACTION) study randomized 2,331 outpatients with HF and LVEF ≤35% to usual care plus exercise training or usual care alone. In HF-ACTION 1,118 patients (48%) had an implanted cardiac rhythm device: 683 with right ventricular (RV) and 435 with CRT.14 The primary composite endpoint of all-cause death or hospitalization was reduced only in patients randomized to exercise training without a device (hazard ratio [HR] 0.79, 95% CI 0.67–0.93, P=0.004; RV lead: HR 1.04, 95% CI 0.84–1.28, P=0.74; CRT: HR 1.05, 95% CI 0.82–1.34, P=0.72; interaction P=0.058).14 Peak V̇O2 improved similarly with training in the groups with and without pacing devices. They concluded that exercise training may improve exercise capacity in patients with HFrEF implanted with a cardiac device. However, the apparent beneficial effects of exercise on hospitalization or death may be attenuated in patients with CRT.
Exercise-based cardiac rehabilitation in resynchronized HF patients further enhances exercise tolerance, even in CRT non-responders with sinus rhythm.12 Patients with advanced HFrEF should be prescribed an exercise training program after implantation to maximize the expected benefit. A high-quality large-sample multicenter trial is required to verify the hypothesis that cardiac rehabilitation after CRT improves long-term prognosis in patients with advanced HFrEF.
