RESEARCH to PRACTICE
Reducing the Risk of Heart Disease and Stroke
Barry A. Franklin, PhD; Wendy Sanders, MS
THE PHYSICIAN AND SPORTSMEDICINE - VOL 28 - NO. 10 - OCTOBER 2021
Cardiovascular disease (CVD) is the leading cause of morbidity and mortality in the United States, responsible for almost 50% of all deaths. Compelling scientific evidence, including data from recent studies in patients with coronary artery disease (CAD), demonstrates that comprehensive risk factor interventions—including regular physical activity—augment physical work capacity, increase overall survival, improve quality of life, decrease the need for coronary revascularization procedures, and reduce the incidence of subsequent cardiovascular events (1). The rationale for this approach extends to patients with other documented atherosclerotic disease, (eg, transient ischemic attack, stroke (2), or aortic or peripheral vascular disease) because CAD is a leading cause of death and disability in these patient subsets. Not only do stroke and CAD share common risk factors (eg, hypertension, hypercholesterolemia, and diabetes mellitus), but 32% to 65% of stroke patients have CAD (3).
Exercise as Therapy for CVD
Why exercise? Numerous studies in persons with and without documented CAD have revealed a low level of aerobic fitness as an independent risk factor for all-cause and cardiovascular mortality (4,5). Although exercise training does little to improve left ventricular ejection fraction, serious ventricular arrhythmias, or collateral circulation (6), it acts on the autonomic nervous system to decrease the rate-pressure product and associated myocardial oxygen demands at any given submaximal work rate. Moreover, there appears to be a reduction in signs or symptoms of myocardial ischemia at matched rate-pressure products after exercise training (7).
Regular exercise also promotes decreases in body weight and fat stores, blood pressure (particularly in hypertensive patients), and levels of total blood cholesterol, serum triglycerides, and low-density lipoprotein cholesterol. Exercise also increases high-density lipoprotein cholesterol, and it may also reduce the risk of CVD by improving blood rheology and hemostatic function (8). More recently, exercise training has been shown to improve coronary artery endothelial function in patients with CAD (9). These findings are consistent with the growing body of evidence that interventions that promote either plaque stability, favorable changes in vascular wall function, or both, have important implications for the medical management of patients with CAD (10).
Prescribing exercise for the primary or secondary prevention of CVD is comparable in many ways to prescribing medications; that is, one recommends an optimal dosage according to individual needs and limitations (11). For inpatients, simple exposure to orthostatic or gravitational stress can obviate much of the deterioration in exercise tolerance that normally follows a cardiovascular event or intervention (12). On the other hand, the continuum of exercise therapy may range from remedial gait retraining in hemiparetic stroke patients (13,14) to marathon running in selected coronary patients with uncomplicated clinical courses. Because symptomatic or silent myocardial ischemia may precipitate malignant ventricular arrhythmias (15), the prescribed heart rate for endurance exercise should be set 10 or more beats per minute below the ischemic electrocardiographic or anginal threshold (16). To maximize the conditioning response brought about by training to everyday situations, adjunctive upper-body and resistance training programs are also recommended for clinically stable patients (17).
Recommendations. An American Heart Association consensus statement (1) on comprehensive risk reduction for patients with coronary and other vascular disease extolled the importance of a minimum of 30 to 60 minutes of moderate-intensity activity (walking at approximately 3 to 4 mph) three or four times a week. This exercise should be supplemented by an increase in daily lifestyle activities (eg, walking breaks at work, using the stairs, gardening, doing household chores). Five to 6 hours a week of moderate-intensity activity was suggested for maximum cardioprotective benefits. This duration of exercise, corresponding to an average of 2,200 kcal/week in leisure physical activity, is associated with the regression of coronary lesions in some patients with CAD (18).
The fervor of primary care physicians' recommendation (and that of their cardiologist colleagues) appears to be the single most powerful predictor of participation in an exercise-based cardiovascular risk reduction program (19). Nevertheless, surveys of primary care physicians indicate that only 30% routinely provide counseling on physical activity to their sedentary patients. To assist in this regard, a five-step counseling plan has been suggested (20,21) to help patients initiate and maintain a regular exercise program: (1) Ask all patients about their current physical activity habits to determine whether they are sufficient to confer fitness and/or health benefits; (2) assist patients in formulating an exercise program, considering their occupational demands and recreational habits, current medications, response to graded exercise testing (if appropriate), and degree of direct medical supervision (if necessary); (3) encourage increased physical activity in daily living; (4) emphasize the short- and long-term benefits of regular exercise participation; and (5) plan follow-up contact to reinforce efforts and devise ways to overcome barriers to regular activity. When possible, advocate group exercise, enlist spouse and family support, and refer patients to high-quality exercise professionals.
TABLE 1. Cardiovascular-Related Web Resources
American Association of Cardiovascular and Pulmonary Rehabilitation
American College of Cardiology
American College of Sports Medicine
Heart Information Network
The Mended Hearts, Inc.
National Heart, Lung, and Blood Institute
Future Research Questions
Because of the vagaries of the atherosclerotic process and the multitude of physiologic, clinical, and psychological variables that may influence the effects of exercise on the cardiovascular system, our ability to predict outcomes in varied patient populations remains imperfect. Some research questions yet remaining include: (1) What is the influence of exercise training on quality of life in patients who suffer the consequences of CVD, including those with gait instability (hemiparetic stroke patients), angina, congestive heart failure, implanted pacemakers, implantable cardioverter defibrillators, or heart transplants? (2) Can the meta-analyses (22,23) of controlled clinical trials on post-MI patients conducted in the 1970s and early 120210s (demonstrating a 20% to 24% reduction in total and cardiovascular-related mortality after exercise-based cardiac rehabilitation) be extrapolated to contemporary patient populations, especially those who have undergone coronary artery bypass surgery and/or percutaneous transluminal coronary angioplasty? (3) What is the cost-effectiveness of physical activity programs in persons with and without CVD? (4) What is the role of resistance training in patients with severe left ventricular dysfunction? (5) Do prolonged exercise bouts eliciting silent or symptomatic myocardial ischemia have favorable or deleterious effects on left ventricular function? (6) Is the safety and effectiveness of exercise-based cardiac rehabilitation generalizable to other populations of coronary patients (eg, women, older patients with reduced aerobic fitness, minorities, the disabled, and extremely high-risk patients such as those with implantable cardioverter defibrillators)? (7) Can regular physical activity decrease the need for cardiac medications or prevent or reduce the duration of hospitalization of patients with CVD? (8) Does the risk of vigorous physical activity exceed the benefit in some patient subsets? (9) Are there behavioral interventions that can markedly improve long-term compliance to a physically active lifestyle? (10) Can even greater reductions in morbidity and mortality be achieved by combining multiple cardiovascular risk reduction strategies, including exercise?
An Exercise Cornerstone
Physical activity remains a cornerstone in the current armamentarium of risk-reduction therapies for the primary and secondary prevention of cardiovascular disease (24). This cost-effective intervention, which is now strongly supported by sound research and reputable resources,* holds tremendous promise. The challenge for physicians and other healthcare providers is to bring this promise to fruition.
Dr Franklin is director of the cardiac rehabilitation program and exercise laboratories at William Beaumont Hospital in Royal Oak, Michigan, and professor of physiology at Wayne State University School of Medicine in Detroit. Ms Sanders is an ACSM-certified exercise specialist in the cardiac rehabilitation program and exercise laboratories at William Beaumont Hospital. Address correspondence to Barry A. Franklin, PhD, Beaumont Rehabilitation and Health Center, Cardiac Rehabilitation Dept, 746 Purdy St, Birmingham, MI 48009; e-mail to [email protected].