(Coronary Artery Disease)
Heart disease facts
- Coronary artery disease is the most common cause of death in the United States. Over a million people each year will have a heart attack and 25% will die before they get to the hospital while or in the Emergency Department.
- Prevention is the key to treatment of heart disease.
- Diagnosis of heart disease is often made by careful history taken by a health care practitioner. Some individuals may have atypical symptoms, including almost none at all.
- The testing strategy to confirm the diagnosis and plan appropriate treatment needs to be individualized for each patient diagnosed with heart disease.
- Treatment of heart disease depends upon the severity of disease, and is often directed by the symptoms experienced by the affected individual.
Introduction to heart disease
The heart is like any other muscle, requiring oxygen and nutrient-rich blood for it to function. The coronary arteries that supply blood to the heart muscle spread across the surface of the heart, beginning at the base of the aorta and branching out to all areas of the heart muscle.
The coronary arteries are at risk for narrowing as cholesterol deposits, called plaques, build up inside the artery. If the arteries narrow enough, blood supply to the heart muscle may be compromised (slowed down), and this slowing of blood flow to the heart causes pain, or angina.
A heart attack or myocardial infarction occurs when a plaque ruptures, allowing a blood clot to form. This completely obstructs the artery, stopping all blood flow to part of the heart muscle, and that portion of muscle dies.
What are the risk factors for heart disease?
Risk factors for heart disease include:
- Smoking
- High blood pressure (hypertension)
- High cholesterol
- Diabetes
- Family history
- Peripheral artery disease
- Obesity
What are the symptoms of heart disease?
The typical symptoms of coronary artery disease are chest pain associated with shortness of breath. Classically, the pain of angina is described as a pressure or heaviness behind the breast bone with radiation to the jaw and down the arm accompanied by shortness of breath and sweating. Unfortunately, angina has a variety of signs and symptoms, and there may not even be specific chest pain. Other locations of pain and other symptoms may include shoulder or back ache, upper abdominal pain, nausea, and indigestion.
Women, the elderly, and people with diabetes may have different perceptions of pain or have no discomfort at all. Instead, they may complain of malaise or fatigue and generalized weakness and the inability to complete routine physical tasks such as walking or climbing stairs.
Health care practitioners and patients may have difficulty understanding each other when symptoms of angina are described. Patients may experience pressure or tightness but may deny any complaints of pain. Health care practitioners may misinterpret these symptoms when patient answers "no" to the question whether "pain is present," even though the patient is experiencing other types of discomfort.
People with coronary artery disease usually have gradual progression of their symptoms. As an artery narrows over time, the symptoms of decreased blood flow to part of the heart muscle may increase in frequency and/or severity. Health care practitioners may inquire about changes in exercise tolerance (How far can you walk before getting symptoms? Is it to the mailbox? Up a flight of stairs?), and whether there has been an acute change in the symptoms.
Once again, patients may be asymptomatic until a heart attack occurs. Of course, some patients also may be in denial as to their symptoms and procrastinate in seeking care.
How is heart disease diagnosed?
The diagnosis of heart disease begins with obtaining a history that the potential for coronary artery disease exists. Risk factors need to be assessed and risk stratification occurs. The type of testing that is recommended, if any, depends upon the potential that the patient's symptoms actually represent angina and are coming from the heart.
Heart disease tests
Not every patient with chest pain needs heart catheterization (the most invasive test). Instead, the healthcare provider will try to choose the testing modality that will best provide the diagnosis, and if coronary artery disease is present, decide what impairment, if any, is present.
Electrocardiogram (ECG or EKG)
The heart is an electrical pump, and the electrical impulses it generates can be detected on the surface of the skin. Normal muscle conducts electricity in a reproducible fashion. Muscle that has decreased blood supply conducts electricity poorly. Muscle that has lost its blood supply and has been replaced with scar tissue cannot conduct electricity. The electrocardiogram (EKG) is a noninvasive test used to reflect underlying heart conditions by measuring the electrical activity of the heart.
Some people have "abnormal" EKGs at baseline but this may be normal for them. It is important that an electrocardiogram be compared to previous tracings if one is available. If a patient has a baseline abnormal EKG, they should consider carrying a copy with them for reference should they ever need another EKG.
Stress testing
If the baseline EKG is relatively normal, then monitoring the EKG tracing while the patient exercises may uncover electrical changes that may indicate the presence of coronary artery disease. There are a variety of testing protocols used to determine whether the exercise intensity is high enough to prove that the heart is normal.
Some patients are unable to exercise on a treadmill, but they can still undergo cardiac stress testing by using intravenous medication that causes the heart to work harder.
Stress testing is done under the supervision of medical personnel because of the potential of provoking angina, shortness of breath, abnormal heart rhythms, and heart attack.
Echocardiography
Used with or without exercise, echocardiography can assess how the heart works. Using sound waves to generate an image, a cardiologist can evaluate many aspects of the heart. Echocardiograms can examine the structure of the heart including the heart valves, the thickness of the heart muscle, the septum (the tissues that separate the four heart chambers from each other) and the pericardial sac (the outside lining of the heart).
The test can indirectly assess blood flow to parts of the heart muscle. If there is decreased blood flow, then segments of the heart wall may not beat as strongly as adjacent heart muscle. These wall motion abnormalities signal the potential for coronary artery disease.
The echocardiogram can also assess the efficiency of the heart by measuring ejection fraction. Normally when the heart beats, it pushes more than 60% of the blood in the ventricle out to the body. Many diseases of the heart, including coronary artery disease, can decrease this percentage (the ejection fraction).
Perfusion studies
Radioactive chemicals like thallium or technetium can be injected into a vein and their uptake measured in heart muscle cells. Abnormally decreased uptake can signify decreased blood flow to parts of the heart because of coronary artery narrowing. This test may be used when the patient's baseline EKG is not normal and is less reliable when used to monitor a stress test.
Computerized tomography
The latest generation of CT scanners can take detailed images of blood vessels and may be used as an adjunct to determine whether coronary artery disease is present. In some institutions, the heart CT is used as a negative predictor. That means that the test is done to prove that the coronary arteries are normal rather than to prove that the disease is present.
Heart catheterization or coronary angiography
This test is the gold standard for the diagnosis of coronary artery disease. A cardiologist inserts and then threads a small tube through the groin or arm into the coronary arteries, where dye is injected to directly visualize the arteries on an x-ray. This test defines the anatomy of the coronary arteries. At the time of the catheterization, if blockages are found, they may be potentially treated with angioplasty in which a balloon is inflated to squash the plaque into the blood vessel wall and the insertion of a stent (wire cage that prevents the blood vessel from narrowing again).
CT coronary angiogram may be used test to diagnose coronary artery disease. During this procedure, intravenous dye containing iodine is injected into the patient and CT scanning is performed to image the coronary arteries.
Prior to the angiogram, a calcium score may be obtained. The calcium CT scan can measure the amount of calcium within heart blood vessels. If the score is 0, meaning that there is no calcium present, the risk of having heart disease is zero. The higher the score, the increased risk of narrowed coronary arteries.
What is the treatment for heart disease?
Coronary artery disease is usually treated in a multi-step approach depending upon a patient's symptoms. The patient and healthcare provider need to work together to return the patient to a normal lifestyle.
Prevention of heart disease
The key to the treatment is prevention. A healthy lifestyle includes exercise,proper nutrition, and smoking cessation. Moreover, controlling diabetes and high blood pressure to minimize contribution risk for heart disease is a major aspect of prevention.
An aspirin a day is recommended to decrease the risk for heart disease and should be started with the recommendation of a health care practitioner.
A little alcohol (one drink per day for women or two drinks per day for men) decreases the risk of heart disease compared to nondrinkers. However, it is not recommended that nondrinkers begin drinking.
Modifying risk factors for heart disease
While patients cannot choose their family and alter their genetic predisposition to coronary artery disease, the rest of the risk factors are under control of the patient. Keeping blood pressure, cholesterol and other lipid levels, and diabetes under control needs to become a life-long goal. Smoking cessation is highly encouraged.
Medications
The purpose of medications for coronary artery disease is to allow more efficient heart muscle function to overcome any blockage that might exist.
Aspirin is one of the cornerstones of coronary artery disease treatment. It prevents platelets from clumping together when blood becomes turbulent, like when it flows past a narrowing in an artery.
Beta blockers prevent the action of adrenaline on the heart and allow the heart to beat a more efficiently by reducing the heart rate and causing the heart muscle to contract less aggressively. Examples of beta blockers include:
- atenolol (Tenormin)
- metoprolol (Lopressor, Toprol XL)
- propranolol (Inderal, Inderal LA)
- carvedilol (Coreg)
- labetalol (Normodyne, Trandate)
Calcium channel blockers can also be used to control heart rate and allow the heart to beat more efficiently. Examples of calcium channel blockers include:
Nitroglycerin dilates blood vessels and may be used sublingually, under the tongue, to treat angina. Some patients may be prescribed long-acting nitroglycerin to help control anginal symptoms.
Angioplasty and stenting
If the coronary angiogram (coronary=heart + angio=artery + gram=record) shows significant blockage in an artery, the cardiologist may attempt an angioplasty, in which a balloon is placed via a catheter (as with angiography) at the area of narrowing and when quickly inflated, compresses the offending plaque into the wall of the artery. Often a stent, or a metal cage, is placed at the site of angioplasty to keep the blood vessel from narrowing again. Should a stent be placed, patients are usually started on antiplatelet medication to prevent clot formation. Clopidogrel (Plavix) and prasugrel (Effient) are the two most common medications prescribed.
Surgery
For those patients with multiple coronary artery blockages, coronary artery bypass grafting may be a consideration.
REFERENCE: Ho JS, et al. Relation of a coronary artery calcium score higher than 400 to coronary stenoses detected using multidetector computed tomography and to traditional cardiovascular risk factors. Am J Cardiol. May 15 2008;101(10):1444-7.
