Coronary Artery Disease
Coronary Artery Disease
The coronary arteries supply a constant flow of oxygen-rich blood to the heart. If plaque builds up in the coronary arteries, blockages develop, blood flow to the heart is reduced, and symptoms occur that range from mild chest pain to a heart attack.
Coronary artery disease (CAD) is the most common form of heart disease, and it affects almost 13 million Americans. CAD and its complications, like arrhythmia, angina pectoris, and heart attack (also called myocardial infarction), are the #1 causes of death in the United States. CAD most often results from a condition known as atherosclerosis, which is the development of a waxy substance build up inside the coronary arteries. This waxy substance, called plaque, is made of cholesterol, fatty compounds, calcium, and a blood-clotting material called fibrin. Two kinds of plaque have been identified: hard and soft.
The effect of hard plaque build up and how it causes heart attacks is well known. If it accumulates in the coronary arteries, blood flow and oxygen delivery to the heart muscle slows or stops. This is what causes a heart attack.
Now researchers are discovering that even though some heart attacks are caused by hard plaque, most heart attacks are caused by soft or “vulnerable” plaque. Vulnerable plaque is an inflamed part of an artery. The inflammation can lead to the formation of a blood clot, and the blood clot then occludes the artery, leading to the heart attack.
What Causes Atherosclerosis?
Researchers believe that atherosclerosis begins when the innermost lining of an artery (the endothelium) is damaged. Arterial damage may be caused by high blood pressure, high levels of cholesterol and triglycerides in the blood, and smoking.
Atherosclerosis may be present for years before causing symptoms. This slow disease process can begin in childhood. In some people, the condition can cause symptoms by the time they reach their 30s. In others, they do not have symptoms until they reach their 50s or 60s. But, as the blockage worsens, the slowed blood supply to the heart begins to cause angina pectoris, a Latin phrase that means “strangling in the chest.” Patients often describe angina as a squeezing, suffocating, or burning feeling in the chest. The pain is generated when the heart has an extra demand for blood, like during exercise or at times of emotional stress.
Angina tends to start in the center of the chest but may move to the arm, neck, back, throat, or jaw. Some patients feel numbness or a loss of sensation in their arms, shoulders, or wrists. An episode usually lasts no more than a few minutes and goes away with rest. Certain patients with CAD do not experience angina. This “silent ischemia,” or lack of oxygen to the heart, does not cause pain.
Several tests are used to diagnose CAD. The choice of which and how many tests to perform depends on the patient’s risk factors, history of heart problems, current symptoms, and the physician’s assessment of these factors. The doctor will begin by compiling a complete medical history, listing symptoms, and listening to the heart with a stethoscope. He or she may then order diagnostic tests, such as a chest x-ray, baseline electrocardiogram (ECG), stress test, exercise thallium test, echocardiogram, angiogram, and positron emission tomography (PET) scanning.
An individual being evaluated for CAD may begin with the simple tests and then progress to more complicated tests or procedures that combine diagnosis and treatment, such as a heart catheterization.
Based on the results of the diagnostic tests, the symptoms of CAD can be treated with medicines, percutaneous transcatheter coronary interventions, and/or surgery. Hospitalization is generally not required to initiate and manage angina with medication. When medical management is either ineffective or when the blockages are severe, a procedure such as angioplasty or heart surgery may be required. Although these very effective treatments are used to treat CAD, none of them is a cure. The blockages or narrowing of the arteries can return or increase unless risk factors are controlled and behaviors are modified.
Many different medicines are used to prevent the discomfort of angina and treat the other symptoms associated with CAD. These medicines work to increase blood flow to the heart muscle or to reduce the heart’s demand for oxygen by slowing heart rate and reducing blood pressure. Aspirin, nitroglycerin, beta blockers, and calcium channel blockers are included in this group.
Intervention Procedures and Surgery
Medicine cannot clear blocked arteries, and a narrowed coronary artery may need treatment to reduce the risk of a heart attack. Two major options are available: percutaneous transcatheter coronary interventions (performed by an interventional cardiologist) or coronary artery bypass surgery (performed by a cardiothoracic surgeon).
Both types of procedures have good track records among carefully selected patients. The decision to go with either option depends on the degree of narrowing, the number of affected arteries, the location of the narrowing, the heart muscle at risk, and individual patient factors (such as age and overall health).
Surgical procedures that may be indicated include coronary artery bypass grafting and transmyocardial laser revascularization.
An ongoing problem with balloon angioplasty is that the blockage returns approximately one-third of the time, usually within six months. This is called restenosis. The restenosis results from the body’s immune system response to the balloon angioplasty procedure (not the progression of the CAD). The use of stents can lower the rate of restenosis to less than 20% to 30% nationally.
Texas Heart Institute www.texasheartinstitute.com/HIC/Topics/Cond/CoronaryArteryDisease.cfm
Hoag Heart Institute www.hoaghospital.org/heartinstitute/Coronary.aspx
American Heart Association www.americanheart.org/presenter.jhtml?identifier=4726