What is a myocardial perfusion scan?
In the United States, one person dies every 36 seconds due to cardiovascular diseases. This fact itself underlines the importance of screening the at risk (vulnerable) population for heart diseases.
A myocardial perfusion scan (radionuclide myocardial perfusion imaging [rMPI] or nuclear stress test) is an imaging technique to study how well the blood flows through the heart muscle. It provides important information about blood flow to the heart muscle at rest and work. A negative scan means there is no underlying hinderance to the blood flow to the heart muscle, whereas a positive scan suggests that the heart muscle is not getting adequate blood supply. A positive test may prompt further surgical management of heart vessel disease by classifying the patient as medium or high risk.
The two techniques for the myocardial perfusion scan are single-photon emission computed tomography (SPECT) and positron emission tomography (PET). The main difference between SPECT and PET scans is the type of radioactive material (radiotracers) used.
How accurate is a myocardial perfusion scan?
A myocardial perfusion scan does not show the actual obstruction in the blood vessels, but depending on the location of the involved muscle, it can indirectly tell your doctor which arteries are affected. These tests can also show a previously missed silent heart attack.
The sensitivity, specificity and accuracy of cardiac imaging with single-photon emission computed tomography (SPECT) is between 44 percent and 70 percent depending on the blood vessels involved. This means that the nuclear stress test or myocardial perfusion scan may miss three out of every 10 patients with severe disease.
In patients with a high risk of heart disease, computed tomography (CT) angiograms are 91 percent to 96 percent accurate and, therefore, are a better first-line test for diagnosis of heart disease than a cardiac perfusion scan.
How is a myocardial perfusion scan performed?
A myocardial perfusion scan is performed as follows
- A myocardial perfusion scan is performed in a resting state and by stressing the heart. The entire procedure can take up to four hours.
- The entire procedure is done under the supervision of a doctor.
- An intravenous (IV) line will be started in your hand or arm and you will be connected to an electrocardiograph (ECG) machine with wires. A blood pressure cuff will be placed on your arm. A tracer (radioactive substance) will be injected into the IV line in your arm. It takes 10 to 60 minutes for the tracer to be absorbed by the body cells. The tracer travels through the bloodstream to the healthy heart muscle. Because only the healthy heart muscle cells can take up this substance, these areas will be eventually highlighted by the tracer. An exercise scan is conducted first. The rest scan is conducted about three hours later.
- The stress study: The heart is subjected to “stress” from exercise by making you run on a treadmill or ride a stationary bicycle at increasing speeds. This activity is continued until you achieve the target or desired heart rate. If you are unable to walk or ride, the heart can be stressed by taking a certain medicine that increases your heart rate or dilates blood vessels mimicking the exercise pattern. You will continue running until the doctor instructs otherwise. You will then be placed into the heart scanner so that a special camera captures your heart images during the stress. If you have any symptoms such as dizziness, chest pain, extreme shortness of breath or severe fatigue at any point during the procedure, let the healthcare provider or technologist know.
- The second set of scans will be taken three to six hours after the first set. During this time, you will not be allowed to eat anything, smoke or drink coffee. In some cases, your doctor may decide to have you return on another day for the second set of scans.
- Rest scan: The second set of scans will be similar to the first set, except that you will not be asked to exercise or given any medicine. You will be given an IV tracer and you will be made to lie on the table while the scanner takes pictures of your heart.
- Once the second set of scans has been completed, the IV line will be removed and you will be allowed to leave.
- Both the resting and stress scan reports are examined and compared. The highlighted area will tell the doctor about the extent to which the heart muscles are well perfused. The scan will also reveal the areas where blood flow is compromised. Your doctor will explain the results and decide on a further course of action.
Health Solutions From Our Sponsors
Johns Hopkins Medicine
American Heart Association
Top How Accurate Is a Myocardial Perfusion Scan Related Articles
Coronary Heart Disease Screening Tests (CAD)
Coronary heart disease or coronary heart disease (CAD) screening tests can be used to potentially prevent a heart attack or cardiac event in a person without heart disease symptoms, and can assist in diagnosing heart disease in individuals with heart disease symptoms. Examples of coronary heart disease tests include:
- electrocardiogram (ECC, EKG),
- exercise stress test,
- radionuclide stress test,
- stress echocardiography,
- pharmacologic stress test,
- CT coronary angiogram, and
- coronary angiogram.
Heart Attack (Myocardial Infarction)A heart attack happens when a blood clot completely obstructs a coronary artery supplying blood to the heart muscle. A heart attack can cause chest pain, heart failure, and electrical instability of the heart.
Heart disease (coronary artery disease) occurs when plaque builds up in the coronary arteries, the vessels that supply blood to the heart. Heart disease can lead to heart attack. Risk factors for heart disease include:
- High blood pressure
- High cholesterol
- Family history
Angina, shortness of breath, and sweating are just a few symptoms that may indicate a heart attack. Treatment of heart disease involves control of heart disease risk factors through lifestyle changes, medications, and/or stenting or bypass surgery. Heart disease can be prevented by controlling heart disease risk factors.
Heart Disease in WomenHeart disease in women has somewhat different symptoms, risk factors, and treatment compared to heart disease in men. Many women and health professionals are not aware of the risk factors for heart disease in women and may delay diagnosis and treatment. Lifestyle factors such as diet, exercise, tobacco use, overweight/obesity, stress, alcohol consumption, and depression influence heart disease risk in women. High blood pressure, high cholesterol, and diabetes also increase women's risk of heart disease. Electrocardiogram (EKG or ECG), stress-ECG, endothelial testing, ankle-brachial index (ABI), echocardiogram, nuclear imaging, electron beam CT, and lab tests to assess blood lipids and biomarkers of inflammation are used to diagnose heart disease. Early diagnosis and treatment of heart disease in women saves lives. Heart disease can be prevented and reversed with lifestyle changes.
CAD SlideshowWhat is heart disease (coronary artery disease)? Learn about the causes of heart disease, arrhythmias and myopathy. Symptoms of heart disease include chest pain and shortness of breath. Explore heart disease diagnosis, treatment, and prevention.
Heart Disease SlideshowHeart disease prevention includes controlling risk factors like diet, exercise, and stress. Heart disease symptoms in women may differ from men. Use a heart disease risk calculator to determine your heart attack risk.
Heart Disease QuizTake our Heart Disease Quiz to get answers and facts about high cholesterol, atherosclerosis prevention, and the causes, symptoms, treatments, testing, and procedures for medically broken hearts.
Am I Having a Heart Attack? Symptoms of Heart DiseaseHeart attacks symptoms vary greatly for men and women, from anxiety and fatigue to nausea and sweating. Learn the warning signs of a heart attack and know the symptoms that may require an immediate trip to the hospital.