Preventing Reinfarction

After a myocardial infarction (MI), most patients are willing to initiate a heart-healthy lifestyle. Motivating them to continue, however, can be challenging.

In our article on page 517, we offered tips on how to help patients quit smoking; we also summarized recent recommendations on drug therapy for secondary prevention. Here we provide strategies to help patients adopt a more heart-healthy diet, increase their exercise/lifestyle activity, and make other needed behavioral changes. We also address psychosocial risk factors—particularly depression—in patients who have had an MI.

A HEART-HEALTHY DIET

A growing body of scientific evidence has implicated several aspects of diet in the pathogenesis of cardiovascular disease (CVD) and its risk factors. The American Heart Association (AHA) recently published the following diet and lifestyle recommendations that should help substantially reduce the risk of both initial and recurrent cardiovascular events¹:

• Balance caloric intake and physical activity to achieve and maintain a healthy body weight (which is defined as a body mass index of 18.5 to 24.9 kg/m²).
• Consume a diet rich in vegetables and fruits.
• Choose whole-grain, high-fiber foods.
• Eat fish, especially oily fish, at least twice a week.
• Choose lean meats, vegetable protein alternatives, and fat-free or low-fat (1% fat) dairy products, and generally avoid partially hydrogenated fats, so as to limit intake of saturated fat to less than 6% of total energy intake, trans fat to less than 1% of energy intake, and cholesterol to less than 300 mg/d.
• Minimize the intake of beverages and foods with added sugars.
• Choose and prepare foods with little or no salt.
• Limit alcohol(ic beverages to no more than 2 drinks a day for men and 1 drink a day for women; ideally, consume alcohol with meals.

"Good" and "bad" foods. A number of foods have been widely heralded as promoting cardiovascular health because they contain various phytochemicals, antioxidants, vitamins (C and D), folate, and fiber (beta-glucan) (Table 1). Foods that are rapidly converted into sugars—such as potatoes and, to a lesser extent, white bread, bagels, and white rice—raise insulin and serum triglyceride levels. Unlike conventional potatoes, sweet potatoes and yams metabolize less rapidly and are less likely to promote hyperglycemia.

Vitamin supplements. The Heart Outcomes Prevention Evaluation (HOPE) trial, which included patients at high risk for cardiovascular events, failed to demonstrate any effect of supplemental vitamin E( on cardiovascular outcomes.² Similarly, 2 recent studies designed to test the hypothesis that lowering homocysteine through supplementation with B vitamins lowers the risk of CVD showed no cardiovascular benefit from folic acid( and vitamin B₁₂ supplements, with or without the addition of vitamin B₆.^3,4 These findings suggest that there is no reason to recommend supplementation with vitamin E or B vitamins for patients with CVD who have a healthful diet.

The AHA does recommend fish oil supplements but only for patients with documented CVD (1 g/d) or hypertriglyceridemia (2 to 4 g/d) and under the supervision of a physician.¹

STRUCTURED EXERCISE AND PHYSICAL ACTIVITY

The benefits of exercise and physical activity in patients with CVD include:

• Increased functional capacity.
• Symptomatic relief of angina.
• Risk-factor reduction.
• Enhanced psychological status.
• Improved quality of life.

The greatest benefits are often reaped by those patients who initially are the most unfit.

Aerobic exercise. Regular aerobic exercise increases patients' ability to consume and utilize oxygen, referred to as their maximal oxygen consumption (VO₂ max) or aerobic capacity. A given task requires a relatively unvarying supply of oxygen, expressed as milliliters of oxygen per kilogram of body weight per minute (mL/kg/min) or as metabolic equivalents (METs; 1 MET equals 3.5 mL O₂/kg/min).

Patients who are not aerobically fit—typical of patients with CVD—may have to work at the high end of their aerobic capacity to perform moderate-intensity leisure-time activities (eg, gardening or walking the dog). Aerobically fit patients need about the same amount of oxygen for these activities, but because they have a higher aerobic capacity, they perform them at a lower percentage of their maximum—and thus with less fatigue and fewer symptoms.

Moderate to vigorous physical activity and improved cardiorespiratory fitness reduce CVD-associated morbidity and mortality by multiple mechanisms. These include antiatherosclerotic, anti-ischemic, antiarrhythmic, antithrombotic, and psychosocial effects of endurance exercise. In addition, adaptations in autonomic control may increase the favorable effects of several of these mechanisms, especially with more vigorous exercise.⁵

Cardiorespiratory fitness is the key to cardioprotection and should be the goal of any aerobic exercise program. Although regular physical activity and improved cardiorespiratory fitness are widely believed to be roughly equivalent in their cardioprotective benefits, a meta-analysis⁶ concluded that the benefits are nearly twice as great for the latter.

Thresholds for improving cardiorespiratory fitness. Considerable evidence supports the recommendation from the CDC and the American College of Sports Medicine (ACSM) that persons with or without CVD should engage in 30 minutes or more of moderate-intensity physical activity on most—and preferably all—days of the week.⁷

What constitutes "moderate- intensity activity" in patients with CVD? Recent studies suggest that the threshold, or minimal effective intensity for improving cardiorespiratory fitness, in persons with CVD is lower than previously thought—about 45% of the oxygen uptake or heart rate reserve.⁸ This corresponds to about 70% of the measured maximal heart rate.

Benefits of brisk walking. Walking is the most accessible and easily regulated exercise that can increase cardiorespiratory fitness and facilitate cardiovascular risk reduction in previously sedentary adults. Moreover, the inherent neuromuscular limits to the speed of walking (and, therefore, the rate of energy expenditure) establish it as the most appropriate form of early unsupervised exercise in patients with CVD. Even at the slowest speeds (eg, less than 2 mph), walking involves an aerobic requirement of at least 2 METs,⁹ which may serve as an adequate aerobic training stimulus in very unfit cardiac patients.

Researchers examined the ability of brisk walking to enable men and women with documented CVD to achieve an aerobic training threshold (more than 70% of the maximal heart rate).¹⁰ A total of 114 men and 28 women, participants in outpatient cardiac rehabilitation programs, were asked to walk a mile as briskly as possible on measured tracks. During the walk, either an ECG telemetry system or a heart rate monitor was used to determine their heart rate. All of the women and 90% of the men achieved an aerobic training threshold; the women averaged 85% of their maximal heart rate as measured during treadmill testing, and the men averaged 79%. These findings suggest that many patients with CVD can improve their cardiorespiratory fitness by brisk walking on level ground.

Lifestyle activities. Despite the widely cited CDC/ACSM exercise guidelines⁸ and a much-heralded Surgeon General's report,¹¹ traditional approaches to getting people to be more physically active (eg, structured exercise programs) have been only marginally effective. Although it was suggested that physicians counsel patients to integrate multiple short bouts of physical activity into their daily lives, data confirming the effectiveness of this recommendation were lacking. However, randomized clinical trials have now shown that a lifestyle approach to physical activity among previously sedentary persons has effects on cardiorespiratory fitness, body composition, and coronary risk factors similar to those of a traditional structured exercise program.^12,13 The Activity Pyramid (Figure) has been suggested as a model that can be used to facilitate adoption of a progressively more active lifestyle. Pedometers, which enhance awareness of physical activity by tallying daily step totals, can also be helpful.

Resistance training. Aerobic exercise should be complemented by flexibility exercises and resistance training. The latter can safely and effectively increase weight-carrying tolerance and muscular strength and endurance, improve cardiovascular function, favorably modify coronary risk factors, and enhance psychosocial and physical well-being in clinically stable coronary patients.¹⁴ Weight training decreases the rate-pressure product associated with the lifting of any load; this may translate to reduced cardiac demands during such occupational and leisure-time activities as carrying groceries or lifting packages.

Although the traditional weight-training prescription involved performing 3 sets of each assigned exercise (with between 6 and 15 repetitions per set), it appears that 1 set results in similar improvements in muscular strength and endurance, especially in novice exercisers. Regimens for patients with coronary disease should include 8 to 10 different exercises involving the upper and lower extremities, at a load that permits 10 to 15 repetitions per set.¹⁴

Risks of vigorous physical exertion. The risk of cardiovascular events (eg, acute MI, sudden cardiac death) appears to increase transiently during vigorous physical activity (requiring 6 METs or more) compared with the risk at other times. This seems to be particularly true among habitually sedentary persons with CVD who engage in unaccustomed vigorous physical exertion. Jogging, racquet sports, other strenuous sports activity, snow removal, and deer hunting are among the activities associated with a greater incidence of cardiac arrest.¹⁵

Warn patients to avoid sporadic bouts of high-intensity physical activity. Also educate them about the warning signs and symptoms (eg, chest pain or pressure, unusual shortness of breath, dizziness or lightheadedness, heart rhythm irregularities) that may signal a deterioration in their clinical status or an impending cardiovascular event. When such symptoms are present, physical activity should be discontinued and medical attention sought.

MODIFICATION OF PSYCHOSOCIAL RISK FACTORS

Character traits, emotional states, and life situations that have been linked to CVD include:

• Depression.
• Anxiety.
• Anger/hostility.
• Social isolation.
• Chronic life stress.¹⁶

These psychosocial factors can directly promote CVD, contribute to the perpetuation of unhealthy lifestyle choices (eg, cigarette smoking or poor diet), and form barriers to successful modification of behavior. Clusters of these factors are often found in patients who have had an MI.¹⁷ Although psychosocial risk factors are frequently overlooked because of the time constraints of a typical primary care practice, identifying and addressing them are essential in patients who have sustained an MI.

Screen all patients who have had an MI for depression. One in five patients hospitalized for MI meets the criteria for major depression.¹⁸ Most patients who have depression in the hospital will still be depressed 1 to 4 months later. Such patients are at a significantly increased risk for subsequent death from both cardiac and noncardiac causes.¹⁸ Although no studies show that treatment for depression improves survival, antidepressants have beneficial effects on surrogate markers of MI risk.¹⁸ Do not be reluctant to refer a patient to a behavioral therapist when additional help is needed.

FACILITATING BEHAVIOR CHANGE

Having an MI can be a terrifying experience. The experience alone may provide the motivation a patient needs to stop smoking, lose weight, exercise, and adopt heart-healthy eating habits. Capitalize on the momentum created by the patient's recent hospitalization, and encourage him or her to start making lifestyle changes immediately.

Although many patients who have had an MI are willing to initiate these changes, motivating them to continue can be challenging. Few patients are able to muster the sustained self-discipline and devise the strategies that will enable them to maintain a heart-healthy lifestyle.

Strategies to promote new behaviors. Adherence to new regimens can be improved by:

• Showing genuine concern through use of a warm and empathic approach.
• Personalizing instructions for each patient.
• Keeping messages consistent from visit to visit.
• Scheduling frequent follow-up appointments to assess progress and reinforce your plan.
• Using each patient encounter as a teaching moment.
• Using the Internet to find handouts to give to patients.
• Instructing your staff to use a step-wise approach with patients and to take care not to overwhelm them.
• Enlisting the help of family members (especially a spouse) to remind and reinforce.
• Allowing patients ample opportunity to express their feelings and beliefs; this can provide tremendous insight and give you the chance to dispel myths that form barriers to change.

Assessing patients' readiness to change. Interventions designed to empower patients to initiate and maintain lifestyle modifications are more effective when they correspond to the patients' readiness to change. According to one model, behavior change encompasses 6 stages, ranging from precontemplation to maintenance.¹⁹ Evaluate patients' stage of readiness before counseling them to change behaviors, and tailor your approach accordingly. Examples of strategies appropriate to the various stages are listed in Table 2.

A technique that can be especially useful in helping patients in the earlier stages of readiness is a type of talk therapy called "motivational interviewing," which is described in the Box. Finally, do not be afraid to ask for help. Cardiac rehabilitation specialists, nutritionists, psychologists, and other health care providers can provide invaluable expertise.