Cardiovascular disease continues to be the leading cause of mortality in the United States for men and women, accounting for one third of all deaths. Nearly 16.3 million Americans have a history of coronary artery disease and 7.9 million have suffered a myocardial infarction. Direct and indirect costs of this condition approach $190.3 billion annually. That is $95.5 billion in direct costs (physicians and other professionals, hospital services, medication, and home health care) and $94.8 billion in indirect costs (lost productivity and mortality). Medical costs for coronary heart disease are projected to increase by 200% over the next 20 years, augmenting the need for widespread availability of cost-effective secondary prevention.

As cardiovascular disease is a substantial cause of disability, physiatrists must be well-versed in all aspects of cardiac rehabilitation. Numerous analyses of evidence-based medical studies have shown cardiac rehabilitation programs to be a safe and effective therapeutic intervention. These secondary prevention programs enhance quality of life and functional status, improve processes of care, and reduce recurrent myocardial infarction, hospitalization, and long-term mortality. Increasingly, cardiac rehabilitation patients have complex medical profiles; thus the need for physiatry involvement is growing. As medical specialists, physiatrists can contribute their unique knowledge and understanding of comprehensive functional assessment to this large patient population, which is in need of such expertise.

Cardiac rehabilitation consists of comprehensive long-term services involving medical evaluation, prescribed exercise, cardiac risk factor modification, health education, counseling, and behavioral interventions. Its short-term goals are to control cardiac symptoms, enhance functional capacity, limit unfavorable psychological and physiologic effects of cardiac illness, and boost psychosocial and vocational status. The long-term goals are to alter the natural history of coronary artery disease, stabilize or reverse the progression of atherosclerosis, and lessen the risk of sudden death and reinfarction.

Indications for cardiac rehabilitation are listed in Table 23–1. Cardiac rehabilitation is considered reasonable and necessary in patients with any of the listed indications within the past 12 months. Additionally, patients with congestive heart failure, sustained ventricular tachycardia or fibrillation, and those who are survivors of sudden cardiac death may be candidates for rehabilitation on a case-by-case basis. Overall, more than 18 million Americans meet the requirements for cardiac rehabilitation.

Cardiac rehabilitation is divided into three phases:

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  Phase 1 is the acute inpatient period, ranging from 1 to 14 days subsequent to the adverse cardiac event. The emphasis of this phase is to prevent the deleterious effects of bed rest. Therapy focuses on range of motion and early mobilization, progressing to activities of 5–7 metabolic equivalents (METs). Upon discharge, the patient enters a transitional period, continuing activities at 5–7 METs, maintaining early mobilization, and gradually increasing endurance and community reintegration. Classically, this time period lasts 6 weeks after acute myocardial infarction to allow for scar formation and ends with a graded exercise stress test. Contemporary approaches allow for exercise training to be initiated sooner than 6 weeks, depending on the medical condition of the patient.

  
  
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  Phase 2 is the outpatient, medically supervised, comprehensive secondary prevention program, including exercise training with electrocardiographic monitoring, based on the parameters determined by the graded exercise stress test. It is typically initiated 1–6 weeks after hospital discharge. Individuals usually advance to activities of 7–8 METs.

  
  
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  Phase 3 is the independent lifelong maintenance period, consisting of regular exercise and lifestyle modifications.

Benefits of cardiac rehabilitation include an increase of tolerated METs and maximal oxygen consumption, a reduction of cardiac symptoms (chest pain, dyspnea on exertion, shortness of breath, and fatigue), a decrease in blood pressure and heart rate for any given level of physical activity, an improvement in blood lipid levels, an enhancement of psychosocial well-being, smoking cessation, and mortality reduction.

A meta-analysis of 48 randomized trials (8940 patients) found that exercise was associated with lower cardiac and all-cause mortality, as well as downward trends for revascularization procedures and nonfatal myocardial infarction. A separate meta-analysis of 63 randomized trials (21,295 patients) found that cardiac rehabilitation reduced recurrent myocardial infarction by 17% at 12 months and reduced mortality by 47% at 2 years.

One study of more than 600,000 Medicare patients hospitalized for acute coronary syndrome, percutaneous coronary intervention, or coronary artery bypass graft surgery found 12.2% of the cohort participated in cardiac rehabilitation. At 1 year, there was a 2.2% mortality rate for cardiac rehabilitation participants versus 5.3% for nonparticipants. The benefit persisted at 5 years, when the mortality rate for participants was 16.3% versus 24.6% for nonparticipants. This considerable risk reduction equals or exceeds the benefit of most drug and procedural interventions. Patients who attended 25 or more sessions had a 20% lower 5-year mortality rate than those who attended fewer than 25 sessions.

Another study of 30,000 patients who participated in at least one cardiac rehabilitation session found a dose-response relationship of cardiac rehabilitation upon followup at 4 years. Patients who attended all 36 sessions were 47% less likely to die and 31% less likely to have a myocardial infarction than those who attended only one session, 22% less likely to die and 23% less likely to have a myocardial infarction than those who attended 12 sessions, and 14% less likely to die and 12% less likely to have a myocardial infarction than those who participated in 24 sessions.

Before the patient begins phase 2 cardiac rehabilitation, several studies are recommended to assess risk, modify the treatment plan, and set exercise parameters for cardiovascular conditioning.

Electrocardiography & Echocardiography

An electrocardiogram (ECG) and echocardiogram are performed as screening tools for cardiac abnormalities such as left ventricular hypertrophy or dysfunction, previous myocardial infarction, conduction abnormalities, and valvular dysfunctions.

Exercise Testing

A. Submaximal Exercise Test

A submaximal exercise test is defined as a peak heart rate of 120 beats per minute, or 70% of the maximum predicted heart rate, and is typically performed 4–6 days after acute injury to provide additional data used in prognosis, activity prescription, and evaluation of medical therapy.

B. Graded Exercise Test

A graded exercise test, also referred to as an exercise tolerance test, should be sign- or symptom-limited and not terminated at a predefined target heart rate or work rate. It is performed at 2–3 weeks postinjury to determine risk stratification (assess prevalence of ischemia or arrhythmias, heart rate, and blood pressure response to exercise), develop an exercise prescription, and quantify functional capacity of the patient. The graded exercise test most commonly utilizes the treadmill. Other modes that are used for patients with arthritis, obesity, or other comorbidities that may preclude an adequate treadmill test include arm ergometry and bicycle ergometry.

Table 23–2 summarizes circumstances in which the graded exercise test might be concluded before the patient reaches a maximal effort. If the test is submaximal, it will yield a lower peak heart rate and a consequential lower training target heart rate. The resultant prescribed exercise intensity will not provide the best possible benefits. In such circumstances, a second graded exercise test at 3–6 weeks postinjury may be performed to ascertain appropriate cardiac rehabilitation parameters.

C. Metabolic Equivalent Level

The peak MET level of patients entering cardiac rehabilitation is 4–6 METs. The Bruce protocol, which is the most frequently used treadmill protocol, is often not the optimal choice as it begins at 4.6 METs and then increases by 2.5–3.0 METs with each 3-minute stage. Cardiac rehabilitation patients should exercise for about 10 minutes to assess functional capacity, heart rate, and blood pressure; however, they are often only able to complete one to two stages (< 6 minutes) of the Bruce protocol. The Modified Bruce protocol starts at 2.3 METs with 1.7 mph at 0% grade then 1.7 mph at 5% grade, but it proceeds with the same work rate profile as the standard Bruce protocol by stage 3 (1.7 mph and 10% grade, or 5 METs). The Naughton–Balke protocol starts at 2 mph at zero grade, speed is held, and the elevation is increased 3.5% every 3 minutes. This is often used for patients with poor exercise tolerance.

Patients with baseline ECG abnormalities due to left bundle branch block, preexcitation syndrome, left ventricular hypertrophy, digoxin therapy (or related medications), greater than 1 mm of resting ST-segment depression, or electronically passed ventricular rhythm may yield a false-positive graded exercise test. In such individuals and in those who are unable to tolerate a standard graded exercise test, pharmacologic stress imaging is needed.

Radionuclide Perfusion Imaging

Radionuclide perfusion imaging can be completed after administration of intravenous thallium-201 or 99m-technetium sestamibi. Images obtained immediately after exercise are compared with images taken at rest to confirm reversible ischemia and scar. If a patient is unable to exercise adequately, an intravenous pharmacologic challenge using agents such as dipyridamole, adenosine, or dobutamine is performed that mimics the cardiac response to exercise, followed by imaging. Echocardiography can be used in conjunction with exercise or dobutamine to assess left ventricular function as well as global and regional wall motion abnormalities associated with transient ischemia occurring during cardiac stress and absent during rest. Stress echocardiography is more sensitive than exercise ECG for the diagnosis of myocardial ischemia.

The graded exercise test carries predictive value for both cardiac and all-cause mortality. Each 1-MET increase in exercise capacity is associated with a 12% improvement in survival. In addition to mortality, the graded exercise test can be used to stratify the patient’s risk for cardiac events during exercise (Table 23–3).

The American Heart Association (AHA) and the American Association of Cardiovascular and Pulmonary Rehabilitation have outlined the core components for cardiac rehabilitation programs (Table 23–4). Each component provides an opportunity by which to improve the overall health and functioning of the cardiac patient.

Patient Assessment