Your doctor may want to consider one or more of these screening tests. They are not routinely performed, but may be advised in some people who are at intermediate risk for a heart attack. These tests may provide additional information about heart attack risk and prompt you and your doctor to treat your risk factors more aggressively. However, none of these tests is a substitute for traditional screening tests.
C-reactive Protein (CRP) Test
CRP is a blood protein whose concentration rises when inflammation is present. Inflammation is associated with an increased risk of a heart attack.
Not everyone needs to have their blood level of CRP measured. According to the American Heart Association, the test is most beneficial for those at intermediate risk for a heart attack. If the test reveals a high CRP level (greater than 2 to 3 mg/L), your doctor may recommend beginning more aggressive measures, such as taking a lipid-lowering medication to achieve a lower LDL cholesterol level. Your doctor may also recommend aspirin to reduce your risk of blood clots.
Elevated blood levels of homocysteine are associated with an increased risk of heart attacks. Your doctor may order a test to measure homocysteine levels in your blood if you have a family history of heart disease but do not have any traditional risk factors such as smoking or high blood pressure.
This blood test measures a recently discovered risk factor for coronary heart disease—an enzyme in the blood called lipoprotein-associated phospholipase A2, or Lp-PLA2. Elevated levels of this enzyme are associated with an increased risk of coronary heart disease, even in people who do not have high LDL cholesterol levels or other risk factors. Your doctor may recommend a PLAC test if he or she is unsure whether to prescribe lifelong aspirin or statin therapy.
Additional Blood Tests: Lp(a) and apoB
Measurements of Lp(a) and apoB may also provide additional information about your heart attack risk. At Johns Hopkins, when someone has an Lp(a) level greater than 30 mg/dL, doctors recommend aiming for an LDL cholesterol level of less than 100 mg/dL. An apoB level higher than your LDL cholesterol level indicates the presence of small, dense LDL particles. High levels of apoB (more than 90 mg/dL) are treated with statins.
Coronary Calcium Scans
This imaging test, also known as electron-beam computed tomography (EBCT) or multidetector computed tomography (MDCT), measures calcium in the coronary arteries. Calcium is often a component of plaques in the arteries and is not found in healthy arteries. Thus, the presence of coronary calcium is an indication of atherosclerosis and possible blockages in the coronary arteries that could trigger a heart attack.
Coronary calcium scans are easy to perform: You lie face up on a table while a circular x-ray is taken. Calcium in the coronary arteries appears as white spots or streaks on the x-rays. A technician then uses a computer program to derive a coronary calcium score: Scores of 1 to 10 reflect arteries largely free from coronary plaques; scores of 11 to 100 indicate mild plaque buildup; scores from 101 to 400 indicate moderate amounts of plaque; and scores above 400 indicate extensive plaque accumulation.
The American Heart Association recommends that coronary calcium scans be considered for individuals at intermediate risk for a heart attack. For those at low or high risk, the scans are unnecessary because the results will likely not alter the treatment plan. In comparison, individuals at intermediate risk who discover that they have significant calcium buildup may decide to begin more aggressive measures to prevent a heart attack. These measures may include taking a statin or aspirin or making more significant lifestyle changes.
Coronary Computed Tomography (CT) Angiography
This noninvasive form of angiography uses multiple x-rays to produce high-resolution, three-dimensional images of the heart and coronary arteries. During the procedure, an iodine-containing contrast dye is infused through a vein in your arm.
While traditional angiography remains the gold standard for assessing blockages in the coronary arteries, CT angiography is a reasonable option for people with symptoms of coronary heart disease who are at intermediate risk for the disease, particularly if the results of a stress test are unclear. However, there are risks in undergoing this test, including radiation exposure and the potential for allergic reactions to the contrast dye. In addition, any detected blockages cannot be immediately treated. You should be carefully evaluated to ensure that the positives outweigh the negatives of using this technology.
Researchers are also testing the effectiveness of CT angiography to rule out heart attacks in people who come to the emergency department with chest pain but whose ECG or blood test results are inconclusive or not available.
Magnetic Resonance Imaging
Cardiac MRI uses powerful magnets and radiofrequency waves, instead of x-rays, to obtain detailed images of the heart and the coronary arteries. The technique allows doctors to examine the size and thickness of the heart’s chambers, determine heart function and the extent of damage from a heart attack or coronary heart disease, and detect blockages in the coronary arteries.
During the test, you will lie on an examination table that is slid into a long, tube-like machine. You must lie very still and may be asked to hold your breath while the technician takes pictures of your heart and coronary arteries. Depending on how many images are needed, the test may take up to one hour. Because of the magnets involved in MRI, some people with pacemakers or implanted defibrillators cannot have the test.