What Is Myocardial Perfusion Scintigraphy (MPS)? How Is It Performed, What Are the Risks, and What Do the Results Mean?

Myocardial Perfusion Scintigraphy (MPS) is a highly sensitive nuclear imaging test that creates a three-dimensional cellular map of the heart by using a low-dose medical tracer administered through a vein to evaluate how well the heart muscle is supplied with blood. Its primary purpose is to detect hidden oxygen-deprived areas within the heart muscle and determine the presence and severity of coronary artery disease. Especially when investigating the cause of symptoms such as chest pain, fatigue, or shortness of breath, it converts the heart’s performance under stress into digital data. In this way, potential risks that could lead to a heart attack are identified in advance, allowing the most appropriate medical steps to protect your health to be taken without delay.

Why Is Myocardial Perfusion Scintigraphy Preferred for Evaluating the Condition of the Heart Arteries?

Our heart is like a very powerful engine that continuously pumps blood to every part of the body. However, for this engine to keep working without interruption, it needs its own fuel, namely oxygen-rich blood. The special vessels that carry this fresh blood to the heart are called the coronary arteries. Sometimes, due to aging, genetic factors, dietary habits, or a stressful lifestyle, deposits known as plaques begin to form on the inner surface of these vessels. Over time, these deposits narrow the inner diameter of the artery, making it more difficult for blood to flow freely.

Today, advanced methods such as angiography and computed tomography are frequently used in diagnosing diseases. These methods allow us to visualize the anatomical structure of the arteries and determine where narrowing or calcification is present. However, simply seeing where the pipe is blocked is not always enough to understand how well the water flowing through that pipe is irrigating the garden.

This is where functional methods that map the heart’s blood supply at the cellular level become important. A coronary narrowing that appears severe may still be delivering enough blood to the heart muscle. Conversely, a narrowing that appears moderate may leave a certain area of the heart significantly deprived of oxygen. This inadequate blood supply, known as ischemia, begins to develop at the cellular level long before symptoms such as chest pain, shortness of breath, or pressure appear. In fact, the cells may begin signaling distress even before any abnormality becomes visible on an electrocardiogram. Detecting these cellular changes accurately and at an early stage provides specialists with an extremely valuable roadmap when deciding whether advanced treatments such as stenting or bypass surgery are necessary.

How Are the Tracers Used in Myocardial Perfusion Scintigraphy Distributed Throughout the Body?

To perform this examination successfully, special tools and markers are required to make the inside of the body visible from the outside. Thanks to advancing technology, sophisticated cameras capable of evaluating the heart’s blood supply in three-dimensional tomographic sections are now used instead of older systems. Moreover, these intelligent systems operate in synchronization with the heart rhythm and can simultaneously evaluate not only blood flow but also the heart’s pumping strength, chamber structure, and wall motion.

During the procedure, special medical tracers containing a very low level of radiation are injected into a vein so they can reach the heart through the bloodstream. Within seconds, these substances reach the heart cells via the circulation and bind to the tissues. The weak signals emitted by these tracers accumulated in the heart tissue are detected by highly sensitive cameras rotating around the patient and converted into detailed digital images.

The primary medical tracers used during the procedure include:

• Thallium compounds
• Technetium compounds

Thallium-based tracers behave similarly to potassium, an element naturally used by cells during normal function, and actively enter the cells. Their disadvantage is that they may sometimes create unwanted shadowing in image quality due to structures such as the diaphragm or thick chest tissue.

Technetium-based tracers are more commonly preferred today. After entering the cells, they remain in place for a longer period and produce stronger signals, significantly reducing the shadowing effect of surrounding tissues. In addition, these substances are eliminated from the body much more quickly. Since the radiation level contained in these tracers is adjusted to remain within internationally accepted diagnostic limits, they are generally not expected to cause permanent cellular damage.

How Should Patients Prepare for a Successful Myocardial Perfusion Scintigraphy?

The preparation process before the test is extremely important to ensure that the results are accurate and reflect the patient’s true condition. There are simple yet highly critical rules that patients should follow at home before the examination. Failure to comply with these instructions may result in inaccurate findings or require the procedure to be postponed to another day.

The main preparation guidelines before the test include:

• Fasting for a specified period
• Avoiding caffeinated beverages
• Not consuming chocolate or chocolate-containing products
• Temporarily discontinuing certain medications under physician supervision

Each of these restrictions has a specific medical reason. Patients are generally asked to arrive with an empty stomach. When the stomach is full, a significant portion of blood flow is directed toward the digestive system, making heart imaging more difficult, while the stomach may produce bright images that obscure the heart.

However, the most important issue is caffeine restriction. In some cases, instead of using a treadmill to stress the heart, special vasodilator medications are administered. These drugs work by binding to specific receptors on the surface of cells. Caffeine, which is found in tea, coffee, carbonated beverages, and chocolate, occupies these receptor sites and physically prevents the medication from binding effectively. If caffeine has been consumed within the hours before the test, the medications may lose much of their intended effect. Likewise, decisions regarding how long before the examination blood pressure or heart rhythm medications should be discontinued must always be planned individually by the supervising physician.

How Are Exercise Testing and Myocardial Perfusion Scintigraphy Performed Together?

Narrowings in the coronary arteries usually do not produce symptoms while a person is watching television at home or performing light daily household activities. This is because the heart’s oxygen demand is quite low during rest, and even a narrowed artery can usually meet this reduced demand. However, when a person climbs stairs, carries a heavy bag, or begins running, the heart’s workload increases rapidly. As the heart pumps more blood, it naturally requires more oxygen and energy. If the narrowed artery cannot meet this increased demand, oxygen deficiency develops within the heart tissue.

To observe this situation safely in a clinical setting, the heart must be stressed under controlled conditions. In individuals who are physically capable, this is usually performed using a treadmill. An estimated target heart rate appropriate for the patient’s age is calculated. Every minute, both the speed and incline of the treadmill are gradually increased. When the heart rate approaches a certain percentage of the target value, the imaging tracer is injected through a vein in the arm.

The purpose of this method is to reproduce under clinical supervision the symptoms the patient experiences during physical activity in daily life. Observing how the coronary arteries perform under natural stress helps identify hidden problem areas. Regions with insufficient blood flow during exercise appear on the images as less bright, pale, or dark areas.

How Is Myocardial Perfusion Scintigraphy Performed in Patients Who Cannot Walk?

Not every patient has the physical ability to use a treadmill or sustain exercise for a certain period. Elderly individuals, those with severe knee, hip, or back disorders, people with neurological conditions that impair balance, or patients who experience severe leg pain due to peripheral arterial disease may be unable to complete an exercise test. In such cases, medications are used to create a stress environment at the cellular level instead of physically stressing the heart.

The primary medications used to stress the heart during this process include:

• Vasodilator medications
• Heart rate–accelerating medications

Vasodilator agents cause the coronary arteries to widen as much as possible. Healthy arteries respond quickly by dilating substantially, increasing blood flow several times above normal. Diseased arteries containing calcification or rigid plaques, however, cannot expand sufficiently. As a result, the difference in blood supply between healthy and diseased areas becomes much more apparent.

Heart rate–accelerating medications place the patient in a condition similar to brisk exercise on a treadmill. Once administered intravenously, the heart rate and pumping strength gradually increase. As oxygen demand rises, the areas supplied by diseased arteries again appear pale on the images. When selecting these medications, accompanying conditions such as asthma, chronic bronchitis, blood pressure disorders, or kidney disease are carefully considered so that the safest option can be chosen for each individual.

How Does the Myocardial Perfusion Scintigraphy Process Work in Patients with a Pacemaker?

The heart contains an extremely delicate electrical network that ensures it beats rhythmically and in coordination. Sometimes, due to aging or previous illnesses, structural conduction abnormalities develop within this network. For example, in a condition called left bundle branch block, small delays occur in electrical transmission between the right and left sides of the heart. Similarly, individuals with implanted pacemakers, whose electrical impulses are generated by the device, may experience contractions that are not fully synchronized between different regions of the heart.

Performing a traditional treadmill exercise test in these individuals may produce misleading findings. As the heart rate increases significantly during exercise, the time available for the heart to relax and receive blood through its own coronary arteries becomes considerably shorter. Due to contraction dyssynchrony, certain areas of the heart wall remain under constant tension, resulting in an unnatural reduction in blood flow. Although there may be no actual blockage in the artery supplying that region, the images may falsely suggest the presence of severe coronary artery disease.

To avoid these diagnostic misconceptions and prevent unnecessary procedures such as angiography, the testing strategy is modified. In patients with pacemakers or specific conduction abnormalities, medications that primarily dilate the coronary arteries are generally preferred instead of methods that significantly increase the heart rate. This approach allows differences in blood supply between vessels to be evaluated without excessively accelerating the heartbeat, greatly reducing the likelihood of misleading results.

How Are Myocardial Perfusion Scintigraphy Results Interpreted in Valve Diseases?

When interpreting the images, not only the coronary arteries but also other structural characteristics of the heart, the condition of the heart valves, and the status of surrounding organs should be considered. The human body is a complex whole, and not every pale area seen on digital images necessarily indicates a major coronary artery blockage. Severe valve regurgitation or marked thickening of the heart walls caused by long-standing high blood pressure can also significantly influence the test results.

Even when the main coronary arteries appear completely open and healthy, microscopic blood vessels within the heart muscle may not function properly due to increased pressure caused by these structural conditions. This microscopic dysfunction of the capillaries may appear on scintigraphy images as generalized reduced blood supply. Particularly in patients with advanced valve disease who are scheduled for cardiac surgery, specialists may choose to bypass this examination altogether and instead proceed directly to imaging techniques that visualize the coronary arteries more directly because of the possibility of misleading results.

In addition, the injected tracers do not accumulate only in the heart tissue. Organs such as the digestive system and especially the liver also absorb some of these substances from the bloodstream. Signals emitted by tracers concentrated in the liver and biliary system may overlap with the lower portions of the heart because of their close anatomical proximity. To avoid false interpretations of ischemia, specialists examine the wall motion of these regions using moving images to confirm whether the tissue is truly healthy.

How Do Myocardial Perfusion Scintigraphy Results Indicate the Risk of a Heart Attack?

After all imaging stages are completed, the collected data are combined using powerful computer systems to create a detailed blood supply map of the heart. If every part of the heart appears adequately, uniformly, and vividly perfused despite the applied stress, this supports the absence of significant coronary artery narrowing capable of impairing blood flow. A normal result provides substantial reassurance and indicates that the likelihood of adverse cardiac events, such as a heart attack in the near future, is very low.

If abnormal or pale regions are detected on the images, the heart muscle is virtually divided into different segments by computer, and the blood supply to each segment is scored. With advancing technology, artificial intelligence software is increasingly being incorporated into this interpretation process, helping detect subtle cellular differences.

Some of the high-risk findings that specialists consider when determining the treatment plan include:

• Extensive ischemic burden
• Transient enlargement of the heart
• Reduced pumping function
• Increased uptake in the lung tissue

Failure of a large region of the heart to receive adequate blood flow during exercise or pharmacologic stress suggests that a substantial portion of the heart muscle may be at risk. Temporary enlargement of the heart during stress often indicates significant narrowing in the main coronary arteries or in multiple vascular territories. Likewise, a marked reduction in the heart’s pumping ability during stress suggests that the heart tissue is under considerable cellular strain. When such high-risk findings are identified, specialists generally prefer proceeding to advanced coronary interventions rather than relying solely on medication.

How Is the Viability of the Heart Muscle Evaluated with Myocardial Perfusion Scintigraphy?

Determining the most appropriate treatment approach is particularly important in patients with long-standing chronic heart failure or those who have previously experienced a major heart attack. Due to prolonged inadequate blood flow, some areas of the heart may have lost their ability to contract over the years. However, a region that appears motionless on echocardiography or ultrasound does not necessarily mean that the cells in that area are permanently dead. Two different scenarios may explain this finding.

In the first scenario, prolonged oxygen deprivation caused by an obstructed artery has resulted in the death of the heart cells, which have been replaced by non-contractile scar tissue. In the second scenario, the cells are still alive but have entered a state resembling hibernation because of severely reduced blood flow, temporarily suspending their contraction to preserve energy and survive. If the cells are already dead, reopening the artery is not expected to significantly improve the heart’s pumping function. However, if the cells are merely hibernating, restoring blood flow with a stent may awaken the heart muscle and allow cardiac function to recover.

Making this distinction accurately is critically important for the patient’s quality of life. Special scintigraphy protocols or PET scans evaluating the cells’ glucose metabolism can determine whether the tissue is completely nonviable or simply dormant. If blood flow appears markedly reduced but cellular metabolic activity continues, this is one of the strongest indicators that the tissue remains viable and encourages specialists to restore circulation by reopening the artery.

Which Treatments Are Performed If Vascular Blockage Is Detected After Myocardial Perfusion Scintigraphy?

If detailed evaluation reveals significant narrowing and high-risk findings within the coronary arteries, the next step is generally to visualize the inside of the arteries directly and correct the problem. During coronary angiography, thin and flexible catheters are advanced to the heart through the groin or wrist, allowing the exact location and anatomical characteristics of the narrowing to be determined. If necessary, procedures to open the artery can often be performed during the same session without requiring open-heart surgery.

The primary interventional methods used to reopen narrowed arteries include:

• Balloon angioplasty
• Bare-metal stents
• Drug-eluting stents
• Drug-coated balloons

During the procedure, a thin wire carrying a deflated balloon is first advanced to the narrowed segment. The balloon is then inflated under high pressure to compress the plaque blocking the artery. Since arteries treated only with balloon dilation tend to narrow again because of their elastic properties, a wire mesh structure called a stent is usually placed at the treated site. The stent acts like a scaffold within the artery, preventing the vessel from collapsing again.

In older bare-metal stents, new layers of cells could develop over time as part of the body’s healing response to the metal, causing the artery to narrow once more. Today, this problem is largely overcome by using stents coated with specialized molecules and medications. These modern stents slowly release medication into the surrounding tissue, suppress unnecessary cell growth, and significantly increase the likelihood that the artery will remain open for many years.

Why Is Follow-Up with Myocardial Perfusion Scintigraphy Important After Stent Placement?

Successful placement of a coronary stent does not represent the end of treatment but rather the beginning of a new period requiring careful follow-up. No matter how advanced drug-eluting stent technology has become, there is always a small possibility that the treated area may narrow again over time. Excessive healing responses to the foreign material or persistently high cholesterol levels may contribute to new narrowing within the stent, either during the first months after the procedure or years later.

If a patient with a stent experiences chest pain or pressure months or years after the procedure, this naturally causes significant concern for both the patient and family members. However, not every episode of chest pain indicates that the stent has become blocked again. Acid reflux, chest wall muscle pain, lung disorders, or significant stress may produce very similar symptoms. To distinguish between these possibilities accurately, specialists generally rely on scintigraphy before proceeding directly to another invasive procedure.

The new scintigraphy images help determine whether the chest pain is truly caused by impaired blood supply to the heart or by another condition unrelated to the heart. If the images appear normal and no new abnormalities are found, the patient is spared unnecessary procedural stress. However, if new cellular oxygen deficiency is detected in the stented region, further intervention may be safely performed using modern techniques such as drug-coated balloons to restore blood flow.

What Should Be Considered After Myocardial Perfusion Scintigraphy and Interventional Procedures?

After the successful completion of diagnostic and interventional treatment processes, the attention patients pay to their own health becomes just as important as the medical interventions themselves. Both the low-dose tracers used during scintigraphy and the contrast agents administered during vascular imaging are eliminated from the body through the kidneys. Therefore, physicians generally recommend drinking more fluids than usual and avoiding dehydration during the first few days after these procedures.

The long-term success of stent placement or balloon angioplasty depends largely on the patient’s willingness to make lasting lifestyle changes. Medical treatments address the existing structural problem, but if the harmful habits that caused the disease continue unchanged, the risk of recurrence in other arteries increases.

The primary lifestyle recommendations for protecting heart health after the procedure include:

• Drinking plenty of water throughout the day
• Taking prescribed medications regularly without interruption
• Quitting smoking and all tobacco products
• Maintaining good blood pressure and blood sugar control
• Following a balanced, vegetable-rich, heart-healthy diet
• Taking regular light walks at the pace recommended by the physician

Patients should never discontinue prescribed blood-thinning or cholesterol-lowering medications without consulting their physician, regardless of how well they feel. Learning to manage stress, avoiding processed foods, and maintaining an active lifestyle all make a substantial contribution to keeping the heart healthy for many years. In addition, even if patients feel completely well, attending regular follow-up appointments greatly facilitates the early detection and treatment of potential problems before they become more serious.

Frequently Asked Questions

Prof. Dr. Kadriye Kılıçkesmez

Prof. Dr. Kadriye Orta Kılıçkesmez is one of the leading figures in the field of Turkish cardiology. She was born on January 24, 1974, in Tekirdağ. After completing her undergraduate education at Istanbul University Cerrahpaşa Faculty of Medicine, she chose cardiology as her specialty and received her specialist training at the Cardiology Institute of the same university. In 2015, she was appointed by the university to establish the Şişli Etfal cardiology clinic and Angio laboratory. Becoming a professor in 2017, Kadriye Kılıçkesmez established the cardiology clinic and Angio laboratory of Prof. Dr. Cemil Taşçı Hospital in 2020 and ensured that the clinic became a training clinic.