Coronary artery disease

LIFE-THREATENING DISORDER

The dominant effect of coronary artery disease (CAD) is the loss of oxygen and nutrients to myocardial tissue because of diminished coronary blood flow. This disease is near epidemic in the Western world.

CAD occurs more commonly in men than in women, in whites, and in middle-aged and elderly people. In the past, this disorder rarely affected women who were premenopausal; however, that’s no longer the case. (See Coronary artery disease and menopause, page 232.)

Causes

Atherosclerosis is the usual cause of CAD. In this form of arteriosclerosis, fatty, fibrous plaques narrow the lumen of the coronary arteries, reduce the volume of blood that can flow through them, and lead to myocardial ischemia. Plaque formation also predisposes to thrombosis, which can provoke myocardial infarction (MI).

Atherosclerosis usually develops in high-flow, high-pressure arteries, such as those in the heart, brain, kidneys, and aorta, especially at bifurcation points. It has been linked to many risk factors: family history, hypertension, obesity,
smoking, diabetes mellitus, stress, a sedentary lifestyle, and high serum cholesterol and triglyceride levels.

Gender Influence: Coronary artery disease and menopause

In women, coronary artery disease (CAD) occurs 10 years later than in men, with a woman’s first heart attack occurring as many as 15 to 20 years later. This may be due to the effects of estrogen before menopause. Estrogen helps keep low-density lipoprotein (LDL), or “bad” cholesterol, levels lower than in men and also helps keep high-density lipoprotein (HDL), or “good” cholesterol, levels higher.

However, recent studies, such as the Heart and Estrogen/progestin Study and the Women’s Health Initiviative Trial, have concluded that hormone replacement therapy doesn’t reduce the risk of cardiovascular effects in postmenopausal women with CAD and should be withheld in these patients. The American Heart Association endorses this position.

Uncommon causes of reduced coronary artery blood flow include dissecting aneurysms, infectious vasculitis, syphilis, and congenital defects in the coronary vascular system. Coronary artery spasms may also impede blood flow. (See Coronary artery spasm.)

Signs and symptoms

The classic symptom of CAD is angina, the direct result of inadequate flow of oxygen to the myocardium. It’s usually described as a burning, squeezing, or tight feeling in the substernal or precordial chest that may radiate to the left arm, neck, jaw, or shoulder blade. Approximately 50% of women don’t present with the typical symptoms of angina. These women experience vague symptoms such as fatigue, shortness of breath, abdominal pain, nausea, or vomiting.

Typically, the patient clenches his fist over his chest or rubs his left arm when describing the pain, which may be accompanied by nausea, vomiting, fainting, sweating, and cool extremities. Anginal episodes most commonly follow physical exertion but may also follow emotional excitement, exposure to cold, or a large meal.

Angina has three major forms:

Stable angina causes pain that’s predictable in frequency and duration and can be relieved with nitrates and rest.
Unstable angina causes pain that increases in frequency and duration. It’s more easily induced.
Prinzmetal’s angina causes unpredictable coronary artery spasm.

Severe and prolonged anginal pain generally suggests MI, with potentially fatal arrhythmias and mechanical failure.

Diagnosis

The patient history—including the frequency and duration of angina and the presence of associated risk factors—is crucial in evaluating CAD. Additional diagnostic measures include the following: