Residency · Residency · Physical Medicine Rehabilitation
Cardiac Rehabilitation: Exercise Prescription and Risk Stratification
Introduction
Cardiac rehabilitation (CR) is a comprehensive, multidisciplinary program that includes exercise training, risk factor modification, education, and psychosocial support. Despite strong evidence demonstrating 20-30% reductions in cardiovascular mortality, cardiac rehabilitation remains significantly underutilized, with only 20-30% of eligible patients participating.
Indications
Acute myocardial infarction. Coronary artery bypass grafting (CABG). Percutaneous coronary intervention (PCI). Stable angina pectoris.
Heart valve repair or replacement. Heart transplantation. Heart failure with reduced ejection fraction (HFrEF). Peripheral arterial disease.
Phases of Cardiac Rehabilitation
Phase I: Inpatient
Begins during hospitalization (1-3 days post-event). Low-level mobilization: Bed exercises, sitting, supervised ambulation. Patient education on activity guidelines, symptom recognition. Psychosocial assessment and support. Discharge planning with home exercise instructions.
Phase II: Outpatient Supervised (6-12 weeks)
ECG-monitored exercise sessions 3 times per week. Structured exercise prescription based on exercise stress test. Risk factor modification: Lipids, diabetes, hypertension, smoking cessation. Nutritional counseling and weight management. Psychosocial interventions for depression and anxiety.
Phase III: Maintenance
Ongoing independent exercise program. Periodic reassessment and program modification. Community-based exercise programs. Long-term risk factor management.
Risk Stratification
Low Risk
Uncomplicated MI or revascularization. Functional capacity greater than or equal to 7 METs. No ischemia, arrhythmias, or heart failure symptoms. EF greater than 50%.
Moderate Risk
Functional capacity 5-7 METs. Mild-to-moderate LV dysfunction (EF 40-49%). ST depression 1-2 mm at high workloads. Inability to self-monitor exercise intensity.
High Risk
EF less than 40%. Complex ventricular arrhythmias. Functional capacity less than 5 METs. Exertional hypotension or hemodynamically significant arrhythmias. Survivors of cardiac arrest. Previous cardiac event with heart failure. 
| Risk Category | EF | Functional Capacity | Key Criteria | Monitoring Level |
|---|---|---|---|---|
| Low | >50% | ≥7 METs | No ischemia/arrhythmia/HF | Minimal ECG monitoring |
| Moderate | 40-49% | 5-7 METs | Mild ST depression at high workload | Intermittent ECG monitoring |
| High | <40% | <5 METs | Complex arrhythmias, exertional hypotension | Continuous ECG monitoring |
Exercise Prescription
Graded Exercise Test (GXT)
Performed before initiating Phase II. Determines functional capacity, ischemic threshold, arrhythmia threshold. Common protocols: Bruce, modified Bruce, Naughton. Used to establish target heart rate and workload parameters.
FITT-VP Principle
Frequency: 3-5 days per week. Intensity: 40-80% of heart rate reserve (HRR) or 40-80% VO2 reserve. Time: 20-60 minutes per session (including warm-up and cool-down). Type: Aerobic (walking, cycling, rowing) and resistance training.
Volume: Progress to 150+ minutes/week of moderate-intensity activity. Progression: Gradual increases in duration before intensity.
Intensity Monitoring Methods
Karvonen formula: Target HR = (HRmax - HRrest) x %intensity + HRrest. Rating of Perceived Exertion (RPE): Borg scale 11-14 (6-20 scale). Talk test: Able to converse but not sing. Keep heart rate 10 bpm below ischemic threshold if applicable.
Resistance Training
Begin 2-3 weeks after aerobic training initiation. 1-3 sets of 10-15 repetitions at 40-60% of 1-RM. 8-10 exercises targeting major muscle groups. Avoid Valsalva maneuver; emphasize proper breathing. Contraindicated with decompensated heart failure or unstable angina.
Special Considerations
Heart Failure
HFrEF patients benefit significantly from CR (HF-ACTION trial). Start at lower intensity (40-50% HRR) with gradual progression. Monitor daily weights, symptoms of decompensation. 6-Minute Walk Test for functional assessment.
Post-Surgical Patients
Sternal precautions for 6-8 weeks after CABG (no pushing/pulling >10 lbs). Upper extremity ROM restrictions during sternal healing. Saphenous vein graft site care for lower extremity. Gradual return to full activities by 8-12 weeks.
Implantable Devices
Pacemaker patients: Use RPE rather than heart rate for intensity monitoring if chronotropically incompetent. ICD patients: Keep heart rate 10-15 bpm below ICD firing threshold. Cardiac resynchronization therapy may improve exercise tolerance.
Outcomes and Benefits
20-30% reduction in cardiovascular mortality. Improved functional capacity (1-2 METs increase). Improved lipid profiles, blood pressure, glycemic control. Reduced depression and anxiety. Improved quality of life and return to work rates. Cost-effective healthcare intervention.
Key Clinical Pearls
- The Karvonen formula using heart rate reserve is preferred over percentage of max heart rate for exercise intensity prescription in cardiac rehabilitation. 2. Exercise should be maintained at 10 bpm below any documented ischemic threshold during graded exercise testing. 3. Resistance training is safe and beneficial in cardiac rehabilitation but should be introduced after establishing an aerobic base and avoiding the Valsalva maneuver. 4. Despite Level 1A evidence, cardiac rehabilitation referral and participation rates remain unacceptably low, representing a significant quality improvement opportunity.
References
- Thomas RJ, Balady G, Banka G, et al. 2018 ACC/AHA clinical performance and quality measures for cardiac rehabilitation. Journal of the American College of Cardiology. 2018;71(16):1814-1837.
- O'Connor CM, Whellan DJ, Lee KL, et al. Efficacy and safety of exercise training in patients with chronic heart failure: HF-ACTION randomized controlled trial. JAMA. 2009;301(14):1439-1450.
- American Association of Cardiovascular and Pulmonary Rehabilitation. Guidelines for Cardiac Rehabilitation and Secondary Prevention Programs. 6th ed. Human Kinetics; 2021.
- Anderson L, Oldridge N, Thompson DR, et al. Exercise-based cardiac rehabilitation for coronary heart disease: Cochrane systematic review and meta-analysis. Journal of the American College of Cardiology. 2016;67(1):1-12.