The objectives of contemporary cardiac rehabilitation are to increase functional capacity, decrease symptoms, reduce disability, improve quality of life, and modify coronary risk factors in an effort to promote plaque stability and/or partial anatomic regression (albeit small, 1 to 5%) of localized coronary artery stenosis to reduce morbidity and mortality. Until recently, the most compelling evidence to support these outcomes came from meta-analyses, using survey data from the 1980s, in postmyocardial infarction patients (primarily middle-aged and older men) who had undergone structured, exercise-based rehabilitation programs. These results, however, cannot necessarily be extrapolated to patients who have had coronary artery bypass graft surgery or percutaneous transluminal coronary angioplasty.1 Moreover, contemporary thrombolytic and revascularization procedures, which markedly decrease early postinfarction mortality, as well as cardioprotective drug therapies (eg, aspirin, beta-blockers, angiotensin-converting enzyme inhibitors, statins) that were not widely available at the time of the earliest trials,2 may serve to diminish the impact of adjunctive exercise-based cardiac rehabilitation programs on survival.3

A recent meta-analysis, including 8940 patients in 48 trials of 6 months or longer of exercise training, added greater numbers of women (20% of the cohort), people age 65 years or older, and patients who had undergone coronary revascularization procedures.4 Compared with usual care, cardiac rehabilitation reduced total and cardiac mortality by 20% and 26%, respectively, with no difference across a number of patient subsets (eg, postmyocardial infarction, postrevascularization, angina pectoris). The intervention also elicited greater improvements in cardiovascular risk reduction in the cardiac rehabilitation group, as verified by substantial decreases in total cholesterol, triglyceride levels, systolic blood pressure, and self-reported cigarette smoking. Importantly, the salutary effect of exercise-based cardiac rehabilitation on total mortality was independent of whether the trial was recent or antedated, suggesting that the mortality benefits of cardiac rehabilitation persist in modern cardiology.5 Similarly, a companion review in the same journal involving 81 studies and 2387 patients with heart failure reported that during the training and follow-up periods, 26 exercising and 41 nonexercising patients died, an outcome that approached statistical significance (odds ratio = 0.71; 95% confidence interval 0.37-1.02; P = .06).6

Although numerous exercise-related cardioprotective mechanisms, including antiatherosclerotic, antithrombotic, anti-ischemic, antiarrhythmic, and psychologic effects (Figure 1) may serve to reduce mortality and recurrent cardiac events,7 these benefits are largely dependent on long-term compliance to exercise and other cardiovascular disease risk-reducing behaviors. Unfortunately, only 11% to 20% of patients with coronary heart disease (CHD) participate in traditional supervised group programs,3 which are associated with increased cost and extended travel time. In one study, patients undergoing gymnasium-based exercise training spent more time in their cars going to and from the programs than patients in a home-training comparison group spent on their cycle ergometers.8 Regardless of sex, adherence rates to structured, exercise-based cardiac rehabilitation programs decline over time. Approximately 25% to 50% of participants drop out within the first 6 months and up to 90% drop out by the end of the first year.9 Moreover, less than 25% of the dropouts continue an exercise regimen sufficient to maintain or improve aerobic capacity.10

Figure 1. Regular physical activity and/or aerobic exercise sufficient to maintain and enhance cardiorespiratory fitness may provide multiple mechanisms to reduce the incidence of initial and recurrent cardiovascular events. [up arrow], increased; [down arrow], decreased; O

It is apparent that major changes will be required in the components and delivery of cardiac rehabilitation services in the era of managed, capitated healthcare.11 These include restructuring and amplifying the services that are currently provided, and offering traditional, supervised group programs and alternative approaches to the delivery of cardiac rehabilitation services to increase their availability. Accordingly, the feasibility, safety, efficacy, and economic impact of these alternate approaches should be assessed in a variety of treatment settings.3

In a prospective cohort study of 438 male coronary patients who participated in a 52-week cardiac rehabilitation program, published in this issue of JCR, Hamm et al12 found that the combination of supervised and unsupervised (predominantly home-based) exercise sessions were effective in improving both directly measured peak oxygen consumption and selected psychosocial outcomes, specifically, role physical scores, with the greatest benefits generally occurring at 38 weeks. For the entire study population (n = 438), an average of only 33 supervised sessions were used, which is slightly less than the usual current practice of 36 consecutive supervised sessions. Moreover, their extended program model, employing 1 supervised session every 7 to 30 days, was associated with a relatively low drop out rate (approximately 30%), no cardiovascular events, and costs that were similar to those for a standard 36-session (12 week) program format. These findings challenge the need for routine, continuous electrocardiographic (ECG) monitored exercise therapy or, for that matter, limiting the program duration to 12 weeks, practices that have largely evolved from Medicare reimbursement rather than clinical efficacy.

Considerable data are available regarding the safety, efficacy, and cost-effectiveness of traditional, supervised group programs.3 Further, supervised programs facilitate patient education both in regard to exercise and lifestyle changes for coronary risk reduction, provide variety and recreational opportunities, and offer staff reassurance and the potential for enhanced adherence, safety, and surveillance. On the other hand, home exercise rehabilitation should be promulgated as an alternative, because of its lesser cost, increased practicability, convenience, and potential to promote independence and self-responsibility.8 For low-risk patients, medically directed, home-based rehabilitation and traditional supervised group programs have shown comparable safety and efficacy. Cardiovascular risk reduction can also be successfully achieved in a home-based rehabilitation setting.13,14 The protocol used by Hamm et al,12 which represented a hybrid of the above-referenced models and emphasized independent exercise, elicited impressive improvements in several important outcome variables over an extended period of time, while maintaining compliance and costs.

Although regular physical activity and improved cardiorespiratory fitness are widely believed to be cardioprotective, a recent meta-analysis concluded that the benefits were nearly twice as great for the latter.15 Indeed, previous studies in persons without known CHD have identified a low level of aerobic fitness as an independent risk factor for all-cause and cardiovascular mortality.16 Recently, Kavanagh and associates extended these data to men17 and women18 with established CHD who were referred for exercise-based cardiac rehabilitation. Directly measured peak oxygen uptake (VO₂ peak) on a cycle ergometer at program entry proved to be a powerful predictor of cardiovascular and all-cause mortality. The VO₂ peak cutoff point above which there was a marked benefit in prognosis was 13 mL/kg/min (3.7 metabolic equivalents [METs]) and 15 mL/kg/min (4.3 METs) in women and men, respectively. Moreover, for each 1 mL/kg/min increase in VO₂ peak there was a 10% reduction of cardiac mortality in women versus 9% in men. Using these data, the 4.4 mL/kg/min increment in VO₂ peak at 38 weeks reported by Hamm et al,12 if maintained, should correspond to a nearly 40% reduction in mortality. Indeed, a recent study of postmyocardial infarction patients with depression or low social support who were followed for up to 4 years, showed that the death rate for patients reporting regular exercise was about half that of the nonexercisers.19 Others have also demonstrated additional improvements in functional capacity, exercise performance, lipids/lipoproteins, and psychosocial well-being when outpatient cardiac rehabilitation was extended beyond 36 sessions over 6 months.20

The findings of Hamm and associates,12 although provocative, are not necessarily generalizable to more diverse populations of patients with stable CHD, particularly elderly patients, those with left ventricular dysfunction, and other patients of higher risk status. Only male patients with reasonable aerobic fitness were studied, and outcomes data were, for the most part, limited to directly measured VO₂ peak and the SF-46 survey,21 which includes 8 health status domains. In addition, the methodology provided little or no information on potentially confounding variables (eg, ejection fraction, comorbid conditions, medication usage, hospitalizations, recurrent revascularizations) as well as the effects of the intervention on conventional risk factors. The investigators also failed to disclose what proportion of "supervised" time was devoted to exercise, education, counseling, risk factor modification, or combinations thereof. Finally, it should be emphasized that cost estimates and conversions (Canadian to US dollars) are highly variable from one facility to another, depending on overhead, ancillary services, reimbursement practices, use (or abuse) of costly ECG monitoring, and staffing mixes.

In conclusion, the secondary prevention of cardiovascular disease must be recognized as a lifetime pursuit and not a formal program of 12 or, for that matter, 38 weeks duration with long-lasting residual effects. The patient must develop the mind-set to change deleterious behaviors and sedentary lifestyles. This process involves a multitude of complex variables, including personal, programmatic, environmental, social and medical factors. Patients should also be counseled to deal with relapses, and to recognize that these behaviors, if infrequent, are not necessarily tantamount to failure. How do we achieve long-term compliance to comprehensive cardiovascular risk reduction therapies? Perhaps the answer lies in the hybrid model developed by Hamm and associates,12 combining the advantages of periodic supervised group sessions with the convenience of medically directed, home-based rehabilitation.

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