About Heart Disease
Heart disease is a condition in which the arteries that supply blood to the muscle of the heart become blocked or impinged by fatty deposits through a process called atherosclerosis. The disease—also known as coronary heart disease (CHD) and coronary artery disease (CAD)—takes time to progress, so early on there are usually no symptoms. Later on, patients may experience chest pain and shortness of breath, at first during exercise and then progressing to resting states. The greatest risk factors associated with the disease are advanced age and obesity; family history is another important risk factor. Physicians use a number of tests for heart disease; most of the tests are non-invasive.
All patients should be given a physical examination by their physician. The physical examination includes a determination of a patient's risk for developing CAD. The patient and his or her physician will discuss symptoms that have been affecting him or her. The doctor will examine the color of the skin, noting any abnormalities. A stethoscope will be used to listen to the patient's heartbeat, and the patient's blood pressure will be measured. Following a physical examination, the patient's doctor will perform a number of diagnostic tests until they have a satisfactory diagnosis of what is ailing the patient.
Physical examinations may include blood work. Blood tests can determine the presence of certain enzymes present in CAD patients or determine if the patient's blood lipid profile puts them at risk for disease.
One of the most standard diagnostic tests performed is the electrocardiograph; the record of the results is called an electrocardiogram (EKG or ECG). This test involves “leads", which are small sensors, being attached to the patients skin on the arms, legs and chest. The sensors measure the rate, strength and direction of the electrical activity of the patient's heart.
Another of the tests for heart disease that is often performed when CAD is suspected is the exercise stress test. Particularly if a patient's coronary arteries are only partially blocked, the patient's heart may receive enough blood at rest, but not necessarily during exercise. The patient may walk or run on a treadmill, pedal an exercise bike, or if unable to use his or her legs, pedal an arm crank. Gradually the speed and resistance are increased, all while having the patient's EKG monitored and the blood pressure measured at regular intervals.
For patients who can not exercise, a drug may be administered to mimic the cardiovascular effects of exercise while monitoring heart function and blood pressure.
Physicians may perform another non-invasive test that uses ultrasonic waves to form a picture of the patient's heart. Several forms of echocardiography exist, and they are widely used due to their low cost, accuracy and harmlessness. Several disorders of the heart, lungs and blood vessels are palpable through use of echocardiograms.
In radionuclide imaging, the doctor injects a small amount of a radioactive substance (radionuclide) into a vein. The substance is allowed to circulate through the patient's vasculature. Then using a gamma camera, a picture is taken, and a computer determines how the radionuclide was distributed throughout the patient's body. If only a small amount is absorbed by the muscular tissues of the heart, it may indicated that the coronary arteries are blocked. Different substances are used as tracers depending upon what type of disorder the physician suspects.
Magnetic Resonance Imaging
Newer magnetic resonance imaging (MRI) machines are able to develop detailed pictures of the heart to detect abnormalities. MRIs use magnetic fields to produce their pictures and are used more frequently to determine problems that were present at birth or distinguish normal tissues from abnormal. These tests are particularly expensive and sophisticated, so they may not be widely available.
Though not widely available, several forms of computed tomography exist to produce pictures of the heart, blood vessels and lungs. Computed tomography is generally faster than MRI and requires an injection of dye to aid in picture development.
In conjunction with cardiac catheterization, coronary angiography is the most accurate test used to diagnose heart disease. The procedure is relatively safe and only minimally invasive. During cardiac catheterization, a small incision is made, usually near the pelvis and a small tube (catheter) is inserted; a local anesthetic numbs the incision site. The catheter is guided through the arteries to the heart. This provides an accurate picture of any atherosclerotic plaques that are blocking the arteries or areas where the artery has narrowed.
Several different tools may be attached to the catheter prior to insertion. If the physician injects dye into the patient's arteries with the catheter, it is called angiography; the dyes are visible in x-rays. The catheter may be used to widen narrowed heart valves in a procedure called valvuloplasty. Or the catheter may manually clear blocked arteries in an angioplasty procedure. Narrowed arteries may have a wire-mesh tube (stent) inserted to keep them from becoming narrow again.
Merck Manual Home Edition: Diagnosis: Symptoms and Diagnosis of Heart and Blood Vessel Disorders
Mayo Clinic: Coronary Artery Disease Diagnosis
Cleveland Clinic: How is CAD Diagnosed?
Cleveland Clinic: Physical Examination
University of Maryland Medical Center: Coronary Artery Disease-Diagnosis
National Heart Lung and Blood Institute: How is Coronary Artery Disease Diagnosed?