Contents:
- Medical Video: Diagnostic Testing for Heart Disease (Q&A)
- What is coronary artery disease?
- 1. Identify "significant" blockages
- 2. Identify plaques that do not cause significant blockages
Medical Video: Diagnostic Testing for Heart Disease (Q&A)
Diagnosing coronary artery disease can challenge both patients and doctors, because so many people are at risk of coronary artery disease and so many tests can be utilized. Who should be tested, and what tests should they undergo?
What is coronary artery disease?
Coronary artery disease is a chronic disease of the coronary arteries. In coronary artery disease, atherosclerosis causes the smooth and elastic arterial path to become hard, stiff, and swollen by "plaque", which is a collection of abnormal calcium, fat, and cell inflammation.
These plaques can protrude in the arterial tract, causing partial blockage of blood flow, a condition that often causes angina. Plaques can also suddenly break, causing blood clots to form in the coronary arteries which results in a sudden blockage of blood flow. Most myocardial infarction (heart attack) due to acute plaque rupture.
Coronary artery disease is a chronic and progressive disease that usually appears for several years before someone realizes something is wrong with them. The first indication that often arises is that there is a problem when an unchangeable event occurs, such as myocardial infarction or heart attack. This means that if you are at high risk of coronary artery disease, you do not have to wait for the symptoms to appear before finding out if you do have a problem.
The following are ways to diagnose if you have coronary artery disease.
1. Identify "significant" blockages
Traditionally, the diagnosis of coronary artery disease has relied on tests that look for evidence of a "significant" blockage in the coronary arteries. In general, the cardiologist considers a "significant" blockage to block 70% or more of the arterial tract.
Sports tests (or stress tests) often help in diagnosing partially blocked coronary arteries. Controlled stress tests are often able to find angina symptoms and characteristic changes to the electrocardiogram (ECG) - findings that indicate that there is a blockage.
Doing a stress test together with the thallium / Cardiolite study or echocardiogram improves the ability to find partially blocked coronary arteries. Thallium and Cardiolite are radioactive substances that are injected into blood vessels during exercise. This substance is channeled into the heart muscle by a coronary artery, allowing the heart image to be displayed with a special camera. If one or more partial coronary arteries are blocked, the area of the heart muscle supplied by the artery appears in the image as a dark spot.
The echocardiogram creates a picture of the heart beating with sound waves. The abnormal heart muscle movement seen on an echocardiogram during exercise is probably coronary artery disease.
If the stress test states that there is one or more blockages, patients are generally referred for cardiac catheterization. The aim of catheterization is to fully characterize the location and extent of all coronary artery blockages, usually with the aim of angioplasty, stenting, or bypass surgery.
Noninvasive tests are being developed that might one day replace the need for cardiac catheterization, including CT scans of multiple incisions and heart MRI. Unfortunately, there is no current approach that can completely replace the need for cardiac catheterization.
2. Identify plaques that do not cause significant blockages
In recent years, cardiologists have learned that unstable myocardia and angina infarction are caused by ruptured plaques in the coronary arteries. It turns out that in most cases, plaque that eventually breaks will be considered "non-significant" (ie it does not cause significant blockages) before rupture. This is why we often hear people suffer from heart attacks immediately after being told that they do not have significant coronary artery disease.
Because any plaque can rupture, it is important to know whether there is plaque — the smallest one. People who have coronary arteries must take steps to stabilize plaque and reduce the risk of plaque rupture. (These measurements often include overcoming risk factors, lifestyle changes, statins, and aspirin.)
Calcium scans are a useful way of detecting the presence of even mild coronary artery disease. A calcium scan is a form of CT scan that can calculate the amount of calcium in a coronary artery. Because calcium usually appears on plaques, measuring the amount of calcium in the arteries gives an indication of whether there is coronary artery disease (and then plaque) and the spread of coronary artery disease.
By warning you that you have at least coronary heart disease enough to produce "silent" plaques, calcium scans can give you the chance to change your lifestyle, and maybe take the right medication, when there is still time to do it.
