Coronary artery disease
Coronary artery disease: Excerpt from Handbook of Diseases
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.
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:
❑ Electrocardiography (ECG) during angina may show ischemia or may be normal; it may also show arrhythmias, such as premature ventricular contractions. The ECG is apt to be normal when the patient is pain-free.
❑ Treadmill or bicycle exercise test may provoke chest pain and ECG signs of myocardial ischemia (ST-segment depression).
❑ Coronary angiography reveals narrowing or occlusion of the coronary artery, with possible collateral circulation.
❑ Myocardial perfusion imaging with thallium-201 or cardiolite during treadmill exercise detects ischemic areas of the myocardium, visualized as “cold spots.”
Treatment
The goal of treatment in patients with angina is to either reduce myocardial oxygen demand or increase oxygen supply. Therapy consists primarily of nitrates, such as nitroglycerin (given sublingually, orally, transdermally, or topically in ointment form), isosorbide dinitrate (given sublingually or orally), beta-adrenergic blockers (given orally), or calcium channel blockers (given orally). Obstructive lesions may necessitate coronary artery bypass surgery and the use of vein grafts.
Angioplasty may be performed during cardiac catheterization to compress fatty deposits and relieve occlusion in patients with no calcification and partial occlusion. (See Relieving occlusions with angioplasty.) A certain risk is associated with this procedure, but its morbidity is lower than that for surgery. Percutaneous transluminal coronary angioplasty may be done in combination with coronary stenting. Stents provide a framework to hold an artery open by securing flaps of tunica media and intima against the artery wall.
UNDER STUDY: Therapeutic angiogenesis is a promising treatment for ischemic heart disease, especially in patients who aren’t candidates for revascularisation. Protein-based therapy with fibroblastic growth factor and vascular endothelial growth factor has produced significant angiogenesis in animal models. The increased perfusion to the ischemic myocardium relieved symptoms and improved cardiac function.
Prevention
Because CAD is so widespread, prevention is of incalculable importance. Dietary restrictions aimed at reducing intake of calories (in obesity) and of dietary fats and cholesterol serve to minimize the risk, especially when supplemented with regular exercise. Abstention from smoking and reduction of stress are also beneficial.
Other preventive actions include control of hypertension (with sympathetic blocking agents, such as methyldopa and propranolol, or diuretics, such as hydrochlorothiazide), control of elevated serum cholesterol or triglyceride levels (with antilipemics, such as HMG-reductase inhibitors, pravastatin sodium, or simvastatin), and measures to minimize platelet aggregation and the danger of blood clots (with aspirin).
Special considerations
❑ During anginal episodes, monitor blood pressure and heart rate. Take an ECG during anginal episodes and before administering nitroglycerin or other nitrates. Record the duration of pain, amount of medication required to relieve it, and accompanying symptoms.
❑ Keep nitroglycerin available for immediate use. Instruct the patient to call immediately whenever he feels chest, arm, or neck pain.
❑ Before cardiac catheterization, explain the procedure to the patient. Make sure he knows why it’s necessary, understands the risks, and realizes that it may indicate a need for surgery.
❑ After catheterization, review the expected course of treatment with the patient and family. Monitor the catheter site for bleeding. Also, check for distal pulses. To counter the diuretic effect of the dye, make sure the patient drinks plenty of fluids. Maintain bed rest.
Clinical tip A collagen substance (Vasoseal, Dengroseal) may be used at the femoral arterial puncture site. Tell the patient to expect to feel a hard bump the size of a large pea.
❑ If the patient is scheduled for surgery, explain the procedure to the patient and family. Give them a tour of the intensive care unit, and introduce them to the staff.
❑ After surgery, monitor blood pressure, intake and output, breath sounds, chest tube drainage, and ECG, watching for signs of ischemia and arrhythmias. Also, observe for and treat chest pain and possible dye reactions. Give vigorous chest physiotherapy and guide the patient in coughing and deep-breathing exercises.
❑ Before discharge, stress the need to follow the prescribed drug regimen (antihypertensives, nitrates, and antilipemics, for example), exercise program, and diet. Encourage regular, moderate exercise. Refer the patient to a self-help program to stop smoking.
Pictures
Book Source Details
- Book Title: Handbook of Diseases
- Author(s): Springhouse
- Year of Publication: 2003
- Copyright Details: Handbook of Diseases, Copyright © 2003 Lippincott Williams & Wilkins.
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Copyright notice for book excerpts: Copyright © 2008 Lippincott Williams & Wilkins. All rights reserved.
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More About This Book:
Title: Handbook of Diseases
Authors: Springhouse
Publisher: Lippincott Williams & Wilkins
Copyright: 2003
ISBN: 1-58255-266-5
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