Cardiac Rehabilitation
Daniel E. Forman
Cardiac rehabilitation is a dynamic and relevant component of the armamentarium for acute coronary syndrome (ACS) management. Because the inflammatory and biological underpinnings of atherosclerotic disease commonly originate from lifestyle and risk factors, the rationale to prioritize exercise and comprehensive secondary prevention has never been more compelling. Nonetheless, cardiac rehabilitation is distressingly underutilized. Adding to such irony, third-party payers are becoming more averse to paying for cardiac rehabilitation. Underutilization may relate to an erroneous perception that cardiac rehabilitation is less important than other ACS interventions, such as revascularization and pharmacological stabilization. Acute interventions provide enhanced myocardial salvage and stability in the short term. Yet, coronary artery disease (CAD) is a chronic process, and unhealthy lifestyle patterns and medical noncompliance in the long term are common and insidious. Functional decline, cognitive impairment, reduced quality of life, recurrent myocardial infarction (MI), angina, heart failure (HF), arrhythmias, and even death are among the many detrimental consequences of CAD, especially when exacerbated by suboptimal lifestyle behaviors. The short-term successes in the management of ACS have led to a growing population of chronic CAD patients who are particularly vulnerable to long-term health consequences. Cardiac rehabilitation is a vital link to a healthier future for ACS patients.
History
Cardiac rehabilitation was first developed approximately 50 years ago amid shifting views regarding early mobilization and activity for MI patients. Until that time, bed rest and sedentary management were promoted with the logic that they helped to reduce ischemia, arrhythmia, recurrent infarction, ventricular aneurysm, and/or myocardial rupture (1). However, seminal research then began to illuminate the unhealthy effects of extended post-MI bed rest, as well as the beneficial effects of early mobilization and exercise (2). Cardiac rehabilitation was formulated as a means to initiate and then advance exercise safely (3). Programs typically included both in-hospital and outpatient formats. The in-hospital model facilitated transition from bed rest to activity as part of the initial CAD (MI or coronary artery bypass graft [CABG]) hospitalization. After hospital discharge, outpatient programming was developed to advance activity and then to foster regular exercise maintenance (4).
Given this context, for many caregivers cardiac rehabilitation solidified in the medical lexicon as exercise supervision (i.e., primarily a means to mobilize safely post-MI or post-CABG patients who were typically feeble and anxious in the midst of prolonged and overwhelming hospitalizations). As such, cardiac rehabilitation was initially endorsed as medically worthwhile because it produced earlier hospital discharge and perhaps even expedited return to work (6).
Justifying cardiac rehabilitation in terms of a vocation probably contributed to a bias that cardiac rehabilitation was suited specifically to employed men. This view overlooked the fact that many others suffered from CAD, and subsequent research showed that return to work after an MI had much more to do with the job itself than to cardiac rehabilitation. Still, patterns quickly became ingrained, and despite multiple studies demonstrating cardiac rehabilitation’s substantial benefits for women, older adults, and ethnically diverse populations, underreferral of these groups relative to white, middle-aged men remains disproportionate (6,7).
Over subsequent years, insights and emphasis regarding risk-factor modification evolved, and cardiac rehabilitation programs broadened to include these objectives. In 1994, the American Heart Association (AHA) formally declared that cardiac rehabilitation was reorganizing into comprehensive secondary prevention programs (8). Blood pressure control, smoking cessation, stress reduction, low-density lipoprotein (LDL) lipid reduction, diet modification, medication adherence (typically beta-blockers, aspirin, angiotensin-converting enzyme (ACE) inhibitors, and statins), and weight loss became parts of aggregate cardiac rehabilitation objectives.
Even with formalized integration of exercise training and risk-factor modification, many caregivers and patients continued to see cardiac rehabilitation primarily as exercise training. The persistence of such a perspective has also likely contributed to today’s mounting under-referral to cardiac rehabilitation. Contemporary CAD treatment standards have brought about shortened hospitalizations, and in so doing, relatively fewer patients are debilitated and enfeebled as a result of ACS hospitalizations. Referral to cardiac rehabilitation based primarily on functional limitation is no longer as relevant.
Amid these changes, home-based cardiac rehabilitation options have also grown in appeal (9,10,11,12,13,14). Home-based programs provide some of the beneficial components of traditional cardiac
rehabilitation, but in a format that many believe is better suited to today’s more rapidly discharged and physically intact ACS patients. Furthermore, home-based training has been touted as better able to extend to patients with logistic constraints (e.g., someone who might not be willing or able to travel to a hospital-based program, such as frail elders who may not drive or who are unable to leave an infirm spouse alone at home). Novel technological advances have added to the appeal of home-based options, as they provide potential to better link home-based patients to one another as well as to hospital personnel (i.e., facilitating community and close supervision without leaving home). Perhaps most significant, many view home-based cardiac rehabilitation as a means to provide key benefits of cardiac rehabilitation with maximal cost efficacy.
rehabilitation, but in a format that many believe is better suited to today’s more rapidly discharged and physically intact ACS patients. Furthermore, home-based training has been touted as better able to extend to patients with logistic constraints (e.g., someone who might not be willing or able to travel to a hospital-based program, such as frail elders who may not drive or who are unable to leave an infirm spouse alone at home). Novel technological advances have added to the appeal of home-based options, as they provide potential to better link home-based patients to one another as well as to hospital personnel (i.e., facilitating community and close supervision without leaving home). Perhaps most significant, many view home-based cardiac rehabilitation as a means to provide key benefits of cardiac rehabilitation with maximal cost efficacy.
Overall, there is a sense of dynamic transition in the field of cardiac rehabilitation. Biological insights about the broad benefits of exercise and risk-factor modification (as both primary and secondary CAD prevention) are escalating just as reimbursements and space allocations within hospitals for cardiac rehabilitation are shrinking. In fact, given many reports of the pleiotropic benefits of exercise (15,16,17) and risk-factor modification (18,19,20,21), the spectrum of patients deemed eligible for cardiac rehabilitation has broadened to include those with HF, peripheral arterial disease (PAD), heart transplant, diabetes, and obesity, as well as those with CAD (ACS patients and/or postrevascularization) (22). Still, most present-day cardiac rehabilitation programs are typically losing money and emphasis, and considerations about the future of cardiac rehabilitation are provoking animated debate. Even among CAD patients, the estimated participation rate is only 10% to 20% of the >2 million eligible patients, and enrollment of patients with other cardiovascular diagnoses is even lower (6). Even among the patients who enroll, 25% to 50% drop out within weeks to months. Home-based cardiac rehabilitation may hold promise for better outreach and application, but these programs have not been standardized, and goals and techniques in home-based cardiac rehabilitation may vary widely from one institution to another.
Given all these complicated currents, we will review standards for traditional outpatient cardiac rehabilitation (i.e., hospital- or clinic-based programs that have been standardized as part of coronary heart disease [CHD] management). Our goal is to consider most worthwhile features that should logically be preserved, even if formats change.
Organization of Traditional Cardiac Rehabilitation
In its most recent scientific statement on the issue, the AHA described cardiac rehabilitation as a coordinated, multifaceted intervention designed to optimize a patient’s physical, psychological, and social functioning, in addition to stabilizing the underlying atherosclerotic processes (22). The guidelines recognize that although in-patient programs once existed for the most infirm and unstable cardiac patients, these have become rare. In most cases, cardiac rehabilitation now refers to an outpatient model, usually allied with a hospital or medical facility that provides ready access to physicians and medical supervision. Standardized programming includes baseline patient assessments (Table 29-1), nutritional counseling, aggressive risk management (including lipids, hypertension, weight, diabetes, and tobacco), psychosocial and vocational counseling, physical activity and exercise training counseling, and reinforcement of evidence-based cardioprotective medications (18).
Eligibility for cardiac rehabilitation applies to CAD and post-MI patients, including those who are revascularized with CABG or percutaneous coronary intervention (PCI), as well as those who are not revascularized. As indicated, eligibility has expanded to include patients with heart transplant, heart failure, PAD, or other forms of cardiovascular disease, including heart valve repair (22). Third-party reimbursement has typically lagged behind broadened enrollment criteria, often creating an unpleasant dimension of financial tension among patients for whom cardiac rehabilitation is clearly indicated. However, medicare expanded coverage includes heart valve repair/replacement, PTZA or stenting, heart or heart-lung transplant MI, CABG, and stable angina pectoris, even for diagnoses for which cardiac rehabilitation is reimbursed, the duration of subsidization (i.e., number of sessions) has typically been truncated, and copayment costs have usually increased. In the past, programs were usually designed to extend for 36 sessions, usually two to three times a week. Today, reimbursement commonly stops after only 10 to 20 sessions, with no particular scientific rationale used to justify this change.
Exercise Training
Exercise training remains a cornerstone of cardiac rehabilitation. Studies have consistently demonstrated improvement in exercise capacity as the result of participation in cardiac rehabilitation. Clinical impacts include expanded daily living activities, self-confidence, and quality of life. Just as important, symptoms related to CAD typically diminish with exercise training, with exercise contributing, at least in part, to greater work efficiency, such that less cardiac work is required for the same (submaximal) level of activity (e.g., lower heart rate and blood pressure for the same workload) (15,16,23).
American Heart Association guidelines for cardiac rehabilitation emphasize that the key objectives for exercise extend beyond functional gains accrued by exercise and have more to do with improving underlying biological and physiological capacities. Exercise improves central cardiac physiology (favorable remodeling along with increased stroke work and cardiac output) as well as peripheral physiology (vascular, skeletal muscle, and endothelial enhancements). Exercise training also modifies atherosclerosis, including inflammation (24,25,26,27,28,29,30). Exercise induces ischemic preconditioning, building resistance to subsequent episodes of ischemic stress (31,32), and reducing thrombotic risk by enhancing intrinsic fibrinolysis (33). Exercise brings about indirect benefits via improvements in blood pressure, lipids, glucose metabolism, weight reduction, and autonomic function (34,35,36,37,38,39).
Exercise training regimens are explicit, with specific modifications for different patient scenarios (e.g., high versus low risk, obesity, deconditioning, advanced age and/or frailty, heart failure/transplant, stroke, and PAD) (40). Both aerobic and resistance training modalities are utilized. Training goals include increasing exercise capacity as well as improved work efficiency, such that myocardial work demands are reduced for a given workload. Furthermore, training objectives now include goals for behavior modification such that long-term exercise adherence is prioritized and more likely achieved.
Exercise is typically prescribed two to four times a week, 30 to 45 minutes a session, at a training intensity based on 60% to 85% of the peak heart rate (HR) or heart rate reserve (an HR training target based on the peak HR assessed relative to the resting HR). Based on traditional 3-month aerobic exercise programs, exercise tolerance on the treadmill increases by 30% to 50% and peak VO2 by 15% to 20% (41). Variations of duration, intensity, and training modalities are anticipated, especially as cardiac rehabilitation has been modified to be
more accessible and effective for a wider range of patients and with more diverse underlying cardiovascular pathologies. Shorter, lower-intensity regimens have been demonstrated to yield significant physiological benefits at the level of the endothelium and skeletal muscle and greater patient adherence. Such considerations may be particularly useful to older patients and or those with HF. Likewise, resistance training provides a key means to modify the weakness and frailty that may otherwise hinder many older rehabilitation patients at the onset of their exercise training (40).
more accessible and effective for a wider range of patients and with more diverse underlying cardiovascular pathologies. Shorter, lower-intensity regimens have been demonstrated to yield significant physiological benefits at the level of the endothelium and skeletal muscle and greater patient adherence. Such considerations may be particularly useful to older patients and or those with HF. Likewise, resistance training provides a key means to modify the weakness and frailty that may otherwise hinder many older rehabilitation patients at the onset of their exercise training (40).
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