Within five years of an initial myocardial infarction (MI), about one in five patients will experience recurrent MI or fatal coronary heart disease (CHD). Given this high recurrence rate, preventing secondary cardiac events is an essential part of care for patients with cardiovascular (CV) disease.

One key to secondary prevention: exercise, whether provided via cardiac rehabilitation (CR) in particular or increased activity in general. Among older patients with documented CHD who undergo CR, mortality rates are generally 21 to 34 percent lower than among nonusers.¹ In certain settings, the mortality benefit could be even greater. At ACC.12, Pack and colleagues (from the Mayo Clinic, Rochester, Minnesota) presented 10-year follow-up data on 869 patients who had coronary artery bypass graft (CABG) surgery. CR attendance was associated with a significant 44 percent reduction in mortality during follow-up (HR = 0.56; 95 percent CI 0.42-0.76; p < 0.001).² Also, there was a significant dose-response relationship between the number of CR sessions attended and CV outcomes.

Given contemporary thrombolytic therapy and urgent revascularization methods, as well as newer cardioprotective drug therapies that markedly diminish early postinfarction mortality, doesn't all this attenuate the impact of adjunctive exercise-based CR? A review of 48 randomized trials concluded that mortality benefits of CR persist in modern cardiology, although such data are suggestive and not definitive.³

Exercise may also be a very beneficial approach for treating depression—a common problem, particularly following acute coronary syndrome (ACS). Epidemiological evidence indicates a proportional relationship between the severity of depressive symptoms and the likelihood of subsequent cardiac events, and patients with even mild depressive symptoms have an increase in mortality risk compared with patients without depression. Recently, Blumenthal et al. conducted a study of patients with varying degrees of depression (half had major depression) and were randomized to group exercise three times per week, 50 to 200 mg sertraline per day, or placebo.⁴ At four-month follow-up, there were comparable reductions in depressive symptoms among the patients who received sertraline and those who underwent exercise. Both groups had greater reductions in depressive symptoms compared with placebo.

Despite the potential survival advantage and related beneficial outcomes, cardiac rehabilitation services remain vastly underutilized among Medicare beneficiaries.

Guidelines: More than CR
Of course, CR is part of recently published ACCF/AHA secondary prevention guidelines¹:

Cardiac Rehabilitation: Class I

• All eligible patients with ACS or whose status is immediately post-CABG or post-PCI should be referred to a comprehensive outpatient cardiovascular rehabilitation program either prior to hospital discharge or during the first follow-up office visit. (Level of Evidence: A)
• All eligible outpatients with the diagnosis of ACS, CABG, or PCI (Level of Evidence: A), chronic angina (Level of Evidence: B), and/or peripheral artery disease (Level of Evidence: A) within the past year should be referred to a comprehensive outpatient cardiovascular rehabilitation program.
• A home-based cardiac rehabilitation program can be substituted for a supervised, center-based program for low-risk patients. (Level of Evidence: A)

 Cardiac Rehabilitation: Class IIa

• A comprehensive exercise-based outpatient cardiac rehabilitation program can be safe and beneficial for clinically stable outpatients with a history of heart failure. (Level of Evidence: B)

However, the guidelines do not limit discussion to CR but also include specific recommendations relating to physical activity:

Physical Activity: Class I

• For all patients, the clinician should encourage 30-60 minutes of moderate-intensity aerobic activity, such as brisk walking, at least five days and preferably seven days per week, supplemented by an increase in daily lifestyle activities (e.g., walking breaks at work, gardening, household work) to improve cardiorespiratory fitness and move patients out of the least-fit, least-active, high-risk cohort (bottom 20 percent). (Level of Evidence: B)
• For all patients, risk assessment with a physical activity history and/or an exercise test is recommended to guide prognosis and prescription. (Level of Evidence: B)
• The clinician should counsel patients to report and be evaluated for symptoms related to exercise. (Level of Evidence: C)

New Paradigm
If CR is not being sufficiently utilized—and it is not—it is imperative that this part of the guidelines focusing on activity not be overlooked either.

Barry A. Franklin, PhD, is director of Cardiac Rehabilitation and Exercise Laboratories at William Beaumont Hospital in Royal Oak, Michigan. He emphasizes "lifestyle activity," a new paradigm in exercise prescription. The traditional model for getting people more physically active (i.e., a regimented exercise program) has been only marginally effective.

As an alternative, he recommends broadening recommendations, from the traditional frequency, intensity, duration, and modes of training that are associated with structured exercise programs, to promoting increased activity in daily living.

Based on available evidence, he also recommends:

• Moderate- to high-intensity resistance training performed 2 to 3 days per week for 3-6 months, which improves muscular strength and endurance in men and women of all ages by 25 to 100 percent (or more), depending on the training stimulus and initial level of strength. (Editor's note: This may be especially important in patients with heart failure given evidence from July 2012 that the benefits of CR are shifting focus from the heart to peripheral skeletal muscle effects that appear to be providing much of the benefits of exercise in this population.)⁵
• Weight training improves CV function: By increasing muscular strength, patients can reduce the heart rate and blood pressure responses (and demands on the heart) when lifting or carrying any given object.
• Brisk walking is of sufficient intensity to elicit a training heart rate in all but the most highly fit patients with heart disease.

The CV benefits of exercise, he said, are broad and include antiatherosclerotic, antithrombotic, antiischemic, and antiarrhythmic effects. In a presentation at ACC.12, Dr. Franklin noted that coronary interventions treat a short segment of the diseased coronary tree, whereas exercise exerts beneficial effects on endothelial function and disease progression in the entire arterial bed.

References

1. Smith SC, Jr, Benjamin EJ, Bonow RO, et al. J Am Coll Cardiol. 2011;58:2432-46. http://content.onlinejacc.org/article.aspx?articleid=1147807
2. Pack QR, Goel K, Lahr B, et al. J Am Coll Cardiol. 2012;59:E1713. http://content.onlinejacc.org/article.aspx?articleid=1205751
3. Taylor RS, Brown A, Ebrahim S, et al. Am J Med. 2004;116:682-92. 
4. Blumenthal JA, Sherwood A, Babyak MA, et al. J Am Coll Cardiol. 2012 August 1. [Epub ahead of print] http://content.onlinejacc.org/article.aspx?articleid=1305794
5. Haykowsky MJ, Brubaker PH, Stewart KP, et al. J Am Coll Cardiol. 2012;60:120-8. http://content.onlinejacc.org/article.aspx?articleid=1212261

To listen to an interview with Barry A. Franklin, PhD, about increasing activity levels as secondary prevention, visit www.youtube.cswnews.org. The interview was conducted by Allan S. Jaffe, MD.

Keywords: Depression, Thrombolytic Therapy, Myocardial Infarction, Acute Coronary Syndrome, Follow-Up Studies, Muscle, Skeletal, Exercise, Peripheral Arterial Disease, Blood Pressure, Secondary Prevention, Outpatients, Heart Failure, Risk Assessment, Coronary Artery Bypass, Disease Progression, Exercise Test

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