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 2000

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
www.aacvpr.org

American College of Cardiology
www.acc.org

American College of Sports Medicine
www.acsm.org

American Heart Association
www.americanheart.org
www.americanheart.org/Heart_and_Stroke_A_Z_Guide

Heart Disease/WEBMD
webmd.lycos.com/condition_center?doi=cvd

Heart Information Network
www.heartinfo.org

Heartpoint
www.heartpoint.com

MEDSCAPE/cardiology
cardiology.medscape.com/Home/Topics/cardiology/cardiology.htm

The Mended Hearts, Inc.
www.mendedhearts.org

National Heart, Lung, and Blood Institute
www.nhlbi.nih.gov

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 1980s (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.

References

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2. Gordon NF: Stroke: Your Complete Exercise Guide. Champaign, IL, Human Kinetics, 1993
3. Roth EJ: Heart disease in patients with stroke: incidence, impact, and implications for rehabilitation, part 1: classification and prevalence. Arch Phys Med Rehabil 1993;74(7):752-760
4. Blair SN, Kohl HW III, Paffenbarger RS, et al: Physical fitness and all-cause mortality: a prospective study of healthy men and women. JAMA 1989;262(17):2395-2401
5. Vanhees L, Fagard R, Thijs L, et al: Prognostic significance of peak exercise capacity in patients with coronary artery disease. J Am Coll Cardiol 1994;23(2):358-363
6. Wenger NK, Froelicher ES, Smith LK, et al: Cardiac Rehabilitation. Clinical Practice Guideline No. 17. Rockville, MD: US Department of Health and Human Services, Public Health Service, Agency for Health Care Policy and Research and the National Heart, Lung, and Blood Institute. AHCPR Publication No. 96-0672, October 1995
7. Balady GJ, Fletcher BJ, Froelicher ES, et al: Cardiac rehabilitation programs: a statement for healthcare professionals from the American Heart Association. Circulation 1994;90(3):1602-1610
8. Eichner ER: Physical activity, coagulability, and fibrinolysis, in Leon AS (ed): Physical Activity and Cardiovascular Health: A National Consensus. Champaign, IL, Human Kinetics, 1997, pp 120-126
9. Hambrecht R, Wolf A, Gielen S, et al: Effect of exercise on coronary endothelial function in patients with coronary artery disease. N Engl J Med 2000;342(7):454-460
10. Franklin BA, Kahn JK: Delayed progression or regression of coronary atherosclerosis with intensive risk factor modification: effects of diet, drugs, and exercise. Sports Med 1996;22(5):306-320
11. Franklin BA: How much exercise is enough for the coronary patient? Preventive Cardiology 2000;3(2):63-70
12. Convertino VA: Effect of orthostatic stress on exercise performance after bedrest: relation to in-hospital rehabilitation. J Cardiac Rehabil 1983;3:660-663
13. Potempa K, Lopez M, Braun LT, et al: Physiological outcomes of aerobic exercise training in hemiparetic stroke patients. Stroke 1995;26(1):101-105
14. Macko RF, DeSouza CA, Tretter LD, et al: Treadmill aerobic exercise training reduces the energy expenditure and cardiovascular demands of hemiparetic gait in chronic stroke patients: a preliminary report. Stroke 1997;28(2):326-330
15. Hoberg E, Schuler G, Kunze B, et al: Silent myocardial ischemia as a potential link between lack of premonitoring symptoms and increased risk of cardiac arrest during physical stress. Am J Cardiol 1990;65(9):583-589
16. American College of Sports Medicine: ACSM's Guidelines for Exercise Testing and Prescription, ed 6. Baltimore, Lippincott Williams & Wilkins, 2000
17. Pollock ML, Franklin BA, Balady GJ, et al: AHA Science Advisory: resistance exercise in individuals with and without cardiovascular disease: benefits, rationale, safety, and prescription. Circulation 2000;101(7):828-833
18. Hambrecht R, Niebauer J, Marburger C, et al: Various intensities of leisure time physical activity in patients with coronary artery disease: effects on cardiorespiratory fitness and progression of coronary atherosclerotic lesions. J Am Coll Cardiol 1993;22(2):468-477
19. Ades PA, Waldmann ML, McCann WJ, et al: Predictors of cardiac rehabilitation participation in older coronary patients. Arch Intern Med 1992;152(5):1033-1035
20. Dunn AL, Marcus BH, Kampert JB, et al: Comparison of lifestyle and structured interventions to increase physical activity and cardiorespiratory fitness: a randomized trial. JAMA 1999;281(4):327-334
21. Andersen RE, Wadden TA, Bartlett, SJ, et al: Effects of lifestyle activity vs structured aerobic exercise in obese women: a randomized trial. JAMA 1999;281(4):335-340
22. Oldridge NB, Guyatt GH, Fischer ME, et al: Cardiac rehabilitation after myocardial infarction: Combined experience of randomized clinical trials. JAMA 1988;260(7):945-950
23. O'Connor GT, Buring JE, Yusuf S, et al: An overview of randomized trials of rehabilitation with exercise after myocardial infarction. Circulation 1989;80(2):234-244
24. Franklin BA, Shephard RJ: Avoiding repeat cardiac events: the ABCDESs of tertiary prevention. Phys Sportsmed 2000;28(9):31-58

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 bfranklin@beaumont.edu.