What is CAD?
Coronary artery disease (CAD) is a progressive chronic disease affecting the endothelial lining of the arterial wall resulting in increased inflammation, accumulation of lipids, macrophages, calcium and fibrous connective tissue.
Over time, the accumulation of plaque leads to vascular stenosis and the impairment or complete obstruction of blood flow. Partial or complete occlusion on a coronary artery may lead to myocardial ischemia, angina and myocardial infarction (MI).
Other risk factors may contribute to the accumulation of plaque and the onset of CAD. These include sedentary lifestyles, hyperlipidemia (specifically LDL-cholesterol), hypertension, family history of heart disease, elevated stress, obesity, diabetes, and smoking.
Managment of CAD
Management of individuals with CAD will vary depending on the severity and stability of the disease. In individuals with unstable disease or advanced lesions greater than 50%, revascularization should be considered as a possible intervention. Revascularization techniques include primary coronary bypass graft (CABG) surgery and percutaneous transluminal coronary angioplasty (PTCA). CABG surgery involves bypassing the obstructed coronary artery with a dissected portion of the saphenous vein or internal mammary artery. The PTCA procedure involves inserting a balloon or dilation catheter in the femoral artery and passing it through the artery until it reaches the site of the occlusion. Inflating the balloon produces plaque compression and stretching of the vessel wall. Often times, a stent will be placed at the site to maintain a patent artery.
The heart relies exclusively on aerobic metabolism. Consequently, any disruption in the delivery of oxygen significantly impairs function. Normally, the heart monitors the relationship between oxygen delivery and oxygen demand. During exercise, the oxygen demand increases as a result of increased myocardial contractility and heart rate. When the ratio of oxygen supply vs. demand is reduced secondary to stenosis or increased demand, tissue hypoxia or myocardial ischemia occurs. Angina occurs when myocardial ischemia causes chest pain or discomfort.
Angina is typically categorized as a heavy squeezing or constricted feeling that typically originates in the sternum and radiates to the shoulders, neck, jaw, and arms. Occasionally, people will experience shortness of breath, nausea, and diaphoresis. When the lumen diameter occluded greater than 70%, the reduced blood flow may not be sufficient to meet the oxygen demands of the heart when the need increases beyond the resting level. Stable angina is typically associated with a known and reproducible level of exertion whereas unstable angina tends to occur at varying levels and is typically addressed with revascularization procedures.
Individuals with stable angina, previous MI, and previous revascularization procedures will all benefit from a comprehensive exercise program and should not necessarily be precluded from endurance sports. As long as they have been cleared by their physician and completed a comprehensive cardiac rehabilitation program, there is no reason individuals with a history of CAD cannot exercise or compete in endurance events.
Special Notes on Medications
- Diuretics do not alter the aerobic capacity
- Beta-blockers decrease submaximal and maximal heart rate and occasionally exercise capacity. Exercise training effect appears unchanged.
- Vasodilators, ACE inhibitors, and angiotensin receptor blockers may result in post-exercise hypotension. Make sure to provide an adequate cool-down.
Benefits of exercise training in individuals with a history of previous MI, PTCA or CABG include:
- Increased maximum VO2 up to approximately 20%
- Improvement in the ventilatory response to exercise
- Improvement in the anaerobic threshold
- Decreased angina symptoms secondary to decreased heart rate and/or blood pressure at any given submaximal level of exercise.
- Increased heart rate variability
- Decreased body weight, body fat, blood pressure, total cholesterol, serum triglycerides and LDL cholesterol.
- Increases in high-density lipoprotein (HDL)
- Decreased risk of MI
- Decreased coronary inflammatory markers
- Increased circulating cells that promote angiogenesis and vascular regeneration
- Decreased blood viscosity, platelet adhesiveness, and fibrinogen.
- Increased vagal tone
In making recommendations for exercise programming, intensity generally corresponds to 40-80% of oxygen uptake reserve or maximal heart rate reserve or using a rating of perceived exertion (RPE) of 11-16 on the Borg scale (6-20).
The frequency of exercise should be at least four to seven sessions per week. Duration of training involves 20-60 minutes of continuous exercise preceded by a warm-up (movement preparation) and followed by a cool down.
Mode of exercise should include activities that involve large muscle mass, is continuous and rhythmical in nature and can be maintained for the prescribed duration.
Examples include cycling, walking/jogging, swimming, and rowing. Strength training in this population should include exercises that are multiplanar and functional in nature, incorporate a component of balance and can be easily incorporated in a circuit training program. It is important to avoid lifting loads that invoke a Valsalva maneuver.
You can learn more about training Special Populations in the Personal Fitness Trainer Certification Course.