Myocardial scintigraphy

Definition: What is a myocardial scintigraphy?

A myocardial scintigraphy is an imaging technique in nuclear medicine and is used to visualize the perfusion of the heart muscle. It involves injecting radioactively labeled drugs, referred to as radiopharmaceuticals, into a vein so they can travel to the heart and accumulate in the heart muscle cells. They emit radiation that can be detected from the outside using a gamma camera.

These images produce a myocardial scintigram, which allows the physician to identify any poorly perfused areas of the heart. Radiopharmaceuticals can only accumulate if the blood vessels are patent and perfusion is intact. The examination is performed both at rest and under stress. It can be useful for various medical conditions and before or after certain medical procedures.

Indications: When is a heart scintigraphy required?

A myocardial scintigraphy is primarily performed when coronary artery disease (CAD) is suspected. CAD involves narrowing of the coronary arteries, which can lead to impaired blood supply to the heart and result in a heart attack (myocardial infarction). Usually, an electrocardiogram (ECG) is performed first. However, in some cases, the ECG findings can be inconclusive or even normal, despite the patient presenting with typical symptoms. In such cases, myocardial scintigraphy can help visualize the actual perfusion of the heart. Moreover, it can determine whether the narrow blood vessels result in a reduced perfusion of the myocardial tissue. In other words, it shows whether the coronary stenosis (narrowed blood vessel) is clinically relevant and may require treatment.

Furthermore, this imaging technique can be used to differentiate between various types of perfusion defects in the myocardium. Narrowed arteries can be treated with stent placement that will restore blood flow. In contrast, if any scar tissue is present, blood flow can no longer be restored because the myocardial cells are no longer viable. Myocardial scintigraphy is therefore also used for follow-up assessments after cardiac catheterization, stent implantation, and bypass surgery.

The examination is covered by both statutory and private health insurance, provided it is medically indicated.

What should be considered before myocardial scintigraphy?

The patient is thoroughly informed about the purpose and potential risks of myocardial scintigraphy before the procedure. Patients should generally fast for at least one hour prior to the examination. In particular, coffee, tea, coke, bananas, chocolate, and smoking should be avoided. Depending on the patient’s preexisting conditions, the treating physician may advise to pause certain heart medications on the day of the examination. This should always be clarified beforehand.

Procedure: What happens during a myocardial scintigraphy?

Myocardial scintigraphy is usually performed under physical stress. This involves the patient riding a stationary bicycle (ergometer) whilst being monitored by an ECG. If that is not possible for medical reasons, certain drugs (e.g., adenosine) can be administered instead to provoke cardiac stress. In either case, a radiopharmaceutical (mostly Tc-99m-MIBI or Tc-99m-Tetrofosmin) is injected intravenously, allowing it to reach the heart during the stress phase. The patient then gets a rest period of 15 to 60 minutes.

After the rest period, imaging (scintigraphy) is performed with the patient lying on their back while a gamma camera records the radiation that is emitted by the radiopharmaceutical. This is often done as a myocardial SPECT, creating three-dimensional images by rotating the gamma camera around the patient, who is placed in a tunnel-shaped device. The scintigraphy takes about 15-30 minutes. A separate scintigraphy is performed to assess myocardial perfusion of the heart at rest, without the stress phase. The radiopharmaceutical is injected, and images are obtained after a resting phase, allowing the radiopharmaceutical to accumulate in the heart muscle. 

Diagnosis: What can be observed on myocardial scintigraphy?

The treating physician receives the scintigram and is able to determine which regions of the heart have taken up large amounts of radiopharmaceutical and are well-perfused, and which show reduced uptake and are poorly perfused. The images make it possible to localize the perfusion deficits within the heart. These are regions that emit less radiation because reduced blood flow means that less radiopharmaceutical reaches these areas. It can be inferred which coronary artery is most likely narrowed and whether multiple vessels are affected. By comparing scintigrams before and after interventional procedures such as stent implantation or bypass surgery, improvement in perfusion in previously underperfused regions can be visualized as they show increased radiopharmaceutical uptake.

Why is the examination performed both at rest and under stress?

When comparing rest and stress scintigrams, it allows the physician to determine whether vessel narrowing causes an underperfusion only during physical exertion or if there is already a perfusion and oxygen deficit at rest. Moreover, it can identify scarred heart muscle, which shows poor perfusion both at rest and under stress, in contrast to reversible storage defects, that are only observed during exertion. The latter indicates coronary artery stenosis, which does not produce symptoms at rest but becomes clinically significant during physical exertion when the oxygen demand of the heart increases. This is referred to as transient myocardial ischemia. 

Risks: How dangerous is heart scintigraphy?

The radiation exposure during myocardial scintigraphy is low (2-8 mSv) because only small amounts of radioactive material are administered, and the radiopharmaceutical is rapidly eliminated from the body, with a half-life of approximately 6 hours. Allergic reactions to the drug are possible but are extremely rare. The procedure should be avoided during pregnancy and breastfeeding and only performed in urgent exceptional circumstances.

Stress scintigraphy involves physical exertion and places a strain on the cardiovascular system. The examination is performed under close monitoring, including continuous ECG, blood pressure, and heart rate measurements. Nevertheless, particularly for patients with preexisting heart conditions, there is a small risk of complications such as cardiac arrhythmias, angina, shortness of breath, leg pain, or even a heart attack. If instead of physical stress a pharmacological stress agent such as adenosine is used, side effects may occur. These include a sensation of warmth, shortness of breath, or palpitation.

Aftercare: What to consider after a myocardial scintigraphy?

The patient is advised to resume taking their heart medications that were temporarily paused, following a stress myocardial scintigraphy. There are generally no other major restrictions after the examination. If no sedative was used, driving a car is not a concern. Moreover, adequate hydration is recommended to promote rapid elimination of the radiopharmaceutical after the procedure. Patients should avoid close physical contact with small children, pregnant women, or breastfeeding mothers for the rest of the day to protect them from any remaining radiation exposure.

Myocardial scintigraphy or cardiac catheterization?

Cardiac catheterization is more invasive compared to myocardial scintigraphy. Even though the former is also a safe routine procedure, it carries certain risks that myocardial scintigraphy does not, such as injury to the coronary arteries or heart muscle, or the occurrence of cardiac arrhythmias. 

The advantage of cardiac catheterization lies in its ability to allow both diagnosis and treatment during the procedure. If a coronary artery is occluded or narrowed during a heart attack, the vessel can be re-opened by inserting a stent through the catheter. Time is of the essence, as a prolonged obstruction of blood flow leads to a progressive loss of heart muscle. Similarly, stenoses or insufficiencies of the heart valves can be treated during cardiac catheterization. In addition, biopsies can be obtained if myocarditis (inflammation of the heart muscle) is suspected.

If there is a risk of an acute heart attack or another condition that requires urgent intervention, cardiac catheterization is indicated. However, for follow-up examinations after a heart attack or to better assess the extent of CAD, myocardial scintigraphy is the safer and preferred method, provided that there is no risk of an acute exacerbation. 

What physicians and clinics specialize in myocardial scintigraphy?

Patients requiring medical care naturally want the best available. Therefore, they ask themselves: Where can I find the best clinic for myself? This question cannot be answered objectively as no reputable physician would claim to be the best. Therefore, one can only rely on a physician’s experience.

We will help you find an expert for your condition. All listed physicians and clinics have been carefully selected based on their outstanding expertise in the field of myocardial scintigraphy and are available to respond to your inquiry.