A Myoview stress test is a type of nuclear heart scan that uses a small amount of a radioactive tracer called technetium-99m tetrofosmin (sold under the brand name Myoview) to create detailed images of blood flow through the heart muscle. The test captures pictures both when the heart is at rest and when it is working hard, and the comparison between those two sets of images reveals whether any areas of the heart are being starved of blood. It is one of the most common ways doctors evaluate suspected coronary artery disease, and understanding what happens during the test, why each step matters, and what the results mean can take a lot of the anxiety out of the experience.
How the Radiotracer Works
Myoview belongs to a class of tracers that were introduced in the 1990s to improve on an older radiotracer called thallium-201. Thallium had been the go-to tracer since the mid-1970s, but it emitted low-energy radiation that made image quality inconsistent, and it lingered in the body longer than ideal. Technetium-99m-labeled tracers, including sestamibi and tetrofosmin (Myoview), solved both problems with a higher-energy signal that cameras can detect more cleanly and a shorter physical half-life that clears from the body faster.1Journal of Nuclear Medicine. Nuclear Cardiac Stress Testing in the Era of Molecular Medicine Only sestamibi and tetrofosmin remain in routine clinical use today.
Once injected into a vein, technetium-99m tetrofosmin travels through the bloodstream and is taken up by heart muscle cells roughly in proportion to the blood flow reaching them. Areas of the heart that receive good blood flow absorb more tracer and light up brightly on the images. Areas that are poorly supplied, whether because of a narrowed artery or scarred tissue from a past heart attack, absorb less and appear as darker spots. The tracer emits gamma rays that a specialized camera (called a SPECT camera, for single-photon emission computed tomography) detects as it rotates around your chest, ultimately producing a three-dimensional map of perfusion across the heart.
What Happens During the Test
A Myoview stress test is really two imaging sessions wrapped around a stress challenge. The exact order can vary by lab, but a common approach is the rest-stress protocol. In this version, you first receive a resting injection of about 296 to 444 megabecquerels of Myoview and then wait 30 to 60 minutes for the tracer to settle into the heart muscle. After that waiting period you lie on a table while the SPECT camera captures the resting images, a process that usually takes 15 to 25 minutes.2Journal of Nuclear Medicine Technology. Let’s Get Physical: Myocardial Stress Tests—A Student’s Perspective
With the resting scan complete, you move to the stress portion. The goal is to make the heart work as hard as possible so that any supply-demand mismatch becomes visible. Once the stress is applied (more on how in the next section), a second, slightly larger dose of tracer is injected at peak stress. You then wait again for the tracer to distribute before a second round of imaging. The interpreting physician compares the stress images to the rest images side by side. A region that looks normal at rest but shows reduced tracer uptake during stress points to a living area of heart muscle that is not getting enough blood when demand rises. A region that looks dark on both sets of images suggests scar tissue from a prior event.
Exercise Stress Versus Pharmacologic Stress
Whenever possible, doctors prefer that you walk on a treadmill or ride a stationary bike to stress the heart, because exercise provides useful information beyond the images themselves. Your blood pressure response, heart-rate recovery, exercise duration, and any symptoms during exertion all tell the cardiologist something about your fitness and risk. But not everyone can exercise hard enough. People with severe arthritis, peripheral vascular disease, deconditioning, or other limitations may not be able to reach the target heart rate needed for a reliable test.
For those patients, a pharmacologic agent is used instead. For many years, adenosine and dipyridamole were the standard drugs for this purpose; they work by dilating the coronary arteries and mimicking what exercise does to blood flow. However, because they activate adenosine receptors broadly throughout the body, they tend to cause side effects like flushing, chest tightness, and shortness of breath. Regadenoson, a newer agent that is more selective in the receptors it targets, has largely replaced them. In the phase 3 ADVANCE clinical trial, regadenoson proved just as effective as adenosine at detecting reversible ischemia while producing fewer unwanted effects.3PubMed Central. Regadenoson Stress Testing: A Comprehensive Review With a Focused Update
The choice between exercise and pharmacologic stress matters beyond comfort. Research comparing outcomes in patients who exercised versus those who received a pharmacologic agent found that, even after adjusting for age and clinical profiles, pharmacologic patients had more than double the risk of dying over follow-up.4PubMed. Association between coronary atherosclerotic burden and all-cause mortality among patients undergoing exercise versus pharmacologic stress-rest SPECT myocardial perfusion imaging That does not mean the drug itself is dangerous. It reflects the fact that people who cannot exercise tend to be sicker to begin with. Still, the finding underscores why doctors generally prefer treadmill testing when it is feasible: the exercise data carry independent prognostic weight.
Preparing for the Test
Your nuclear cardiology lab will give you specific instructions, but a few preparation steps are nearly universal. If the stress portion will use a pharmacologic vasodilator like regadenoson or adenosine, you will be asked to avoid all caffeine for at least 12 to 24 hours beforehand.5PubMed. Effect of caffeine on myocardial perfusion imaging using single photon emission computed tomography during adenosine pharmacologic stress Caffeine blocks the same adenosine receptors the drug is trying to activate, which can blunt the vasodilatory effect and make the test unreliable. Coffee, tea, energy drinks, chocolate, and even some over-the-counter pain medications contain enough caffeine to interfere. For exercise stress testing, caffeine restriction is less critical, but many labs enforce it anyway to keep their protocols uniform.
You will also typically be told to avoid eating a heavy meal for a few hours before the test, partly to reduce nausea during exercise and partly because a full stomach can push the diaphragm upward and interfere with the camera’s view of the heart. Some cardiac medications, particularly beta-blockers and calcium channel blockers, may be held before the test if the goal is to reach a high heart rate on the treadmill, but that decision is always made by your referring physician. Wear comfortable clothes and walking shoes if you are doing the exercise version.
How Accurate Are the Results?
No test is perfect, and a Myoview stress test is no exception. In a study of patients who could not exercise adequately and instead received dobutamine (another pharmacologic stressor) followed by tetrofosmin imaging, the test picked up coronary artery disease with a sensitivity of about 80 percent and a specificity of about 72 percent, yielding an overall accuracy of roughly 77 percent.6PubMed. Dobutamine technetium-99m tetrofosmin SPECT imaging for the diagnosis of coronary artery disease in patients with limited exercise capacity In plain terms, the test correctly identified disease in about four out of five people who had it, and correctly cleared about seven out of ten people who did not. Those numbers are broadly representative of nuclear perfusion imaging, though accuracy can shift depending on the patient population, the stress method, and the camera technology used.
Where the Myoview stress test really shines is in its prognostic power. A meta-analysis of exercise-based myocardial perfusion studies found that when the test comes back normal, the risk of heart attack or cardiac death over the next three years is only about 1.2 percent, giving the test a negative predictive value near 99 percent.7Journal of the American College of Cardiology. The Prognostic Value of Normal Exercise Myocardial Perfusion Imaging and Exercise Echocardiography: A Meta-Analysis A large multicenter registry that specifically tracked patients imaged with tetrofosmin reported an annualized cardiac death rate of just 0.6 percent among those with a normal scan, and overall cardiac survival exceeded 99.5 percent after controlling for age, sex, and the type of stress used.8Journal of Nuclear Medicine. Prognostic Value of Normal Exercise and Adenosine 99mTc-Tetrofosmin SPECT Imaging: Results from the Multicenter Registry of 4,728 Patients Conversely, an abnormal scan predicted a significantly higher long-term risk of cardiac events, and the specific pattern of abnormality added information beyond what clinical history and exercise testing alone could provide.9PubMed Central. Long-term prognostic value of exercise technetium-99m tetrofosmin myocardial perfusion single-photon emission computed tomography
In other words, the test’s greatest practical value often lies in reassurance. A normal Myoview stress test is a strong signal that your heart’s blood supply is adequate and your near-term risk is low.
What Can Go Wrong With the Images
One of the most common headaches in nuclear cardiology is attenuation artifacts. These are dark spots on the images caused not by poor blood flow but by soft tissue between the heart and the camera absorbing some of the gamma rays before they reach the detector. The result can mimic a real perfusion defect and lead to a false-positive reading if the interpreting physician is not paying close attention.
The pattern of these artifacts depends heavily on body type and sex. In supine (lying-down) imaging, inferior-wall attenuation from the diaphragm was present in about 78 percent of men, while anterior-wall attenuation from breast tissue appeared in roughly 51 percent of women.10PubMed Central. Soft Tissue Attenuation Patterns Associated with Supine Acquisition SPECT Myocardial Perfusion Imaging: A Descriptive Study When imaging is done in the upright position instead, the pattern shifts: inferior attenuation becomes even more common (about 64 percent of cases) while anterior attenuation drops substantially.11The Open Cardiovascular Medicine Journal. Soft Tissue Attenuation Patterns Associated with Upright Acquisition SPECT Myocardial Perfusion Imaging: A Descriptive Study Obesity amplifies lateral-wall artifacts as well.
Modern labs address these artifacts in several ways. Many SPECT systems now include a low-dose CT scanner that generates an attenuation map, which the software uses to mathematically correct for soft-tissue absorption. Some labs image patients in two positions (supine and prone, or supine and upright) and compare the two: a defect that appears in one position but disappears in the other is almost certainly an artifact, while a true perfusion defect persists in both. Knowing what to expect based on a patient’s sex and body habitus helps experienced readers avoid false alarms.
Beyond Blood Flow: The Ejection Fraction and Gated Imaging
Because the tracer stays in the heart muscle for a while after injection, labs can “gate” the SPECT acquisition to the heartbeat using an ECG signal. By capturing images at multiple points in the cardiac cycle, the software reconstructs a beating-heart movie from which it calculates the left ventricular ejection fraction, or the percentage of blood the heart pumps out with each beat. It also measures end-diastolic and end-systolic volumes. Research using tetrofosmin specifically has confirmed that these gated measurements are repeatable, particularly in patients with reduced heart function, as long as the image counts are adequate.12PubMed. Repeatability of left ventricular ejection fraction and volume measurement for 99mTc-tetrofosmin gated single photon emission computed tomography (SPECT)
This functional information is clinically useful in its own right. A low ejection fraction at rest or a drop in ejection fraction from rest to stress can indicate widespread ischemia or weakened heart muscle, adding another layer to the risk picture. Because the data come from the same scan, there is no additional radiation or separate appointment involved.
Radiation Dose in Context
A common concern is the radiation you receive during the test. With older protocols using higher tracer doses and two-day imaging, the effective dose could reach 10 to 15 millisieverts (mSv), comparable to a few years of natural background radiation compressed into one day. Newer camera technologies and optimized protocols have brought that down dramatically. Using a high-efficiency camera and a stress-first approach, one study found that a complete rest-and-stress study averaged about 2.2 mSv, and roughly 70 percent of patients whose stress images looked normal did not need the rest portion at all, dropping the dose to about 1 mSv.13Journal of Nuclear Medicine. Radiation Dose and Prognosis of Ultra-Low-Dose Stress-First Myocardial Perfusion SPECT in Patients with Chest Pain Using a High-Efficiency Camera For perspective, 1 mSv is less than half the annual background radiation most people absorb just from living on Earth.
Not every lab has the latest solid-state cameras that allow these ultra-low doses, so if radiation exposure concerns you, it is reasonable to ask your facility what their typical effective dose is. Even with conventional equipment, the dose from a single Myoview study is well within the range considered safe for a diagnostic test where the clinical benefit of knowing whether your heart is ischemic clearly outweighs the tiny statistical increase in cancer risk from a low dose of radiation.
How the Test Performs in Obese Patients
Obesity introduces challenges for almost every cardiac imaging modality, and nuclear stress testing is no exception. Soft-tissue attenuation is more pronounced, and the tracer signal has to travel through more tissue to reach the camera, which can degrade image quality. Despite these hurdles, a study that specifically evaluated obese patients undergoing tetrofosmin imaging found that the test still separated risk effectively. Among obese patients with a normal perfusion scan, the annual cardiac death rate was 0.6 percent, compared with 3.3 percent per year in those with abnormal perfusion. Perfusion abnormalities independently predicted both cardiac and overall mortality in this group.14Journal of Nuclear Medicine. Prognostic Stratification of Obese Patients by Stress 99mTc-Tetrofosmin Myocardial Perfusion Imaging
In practice, labs may use higher tracer doses for larger patients, image in multiple positions to reduce artifact confusion, or rely more heavily on CT-based attenuation correction. The test remains a viable option for this population even though the images require more careful interpretation.
Incidental Findings on the CT Scan
If your SPECT study includes a low-dose CT for attenuation correction, the CT images capture more than just the heart. The field of view typically includes parts of the lungs, mediastinum, upper abdomen, and spine. Research has shown that nearly 70 percent of these attenuation-correction CT scans contain some kind of extracardiac finding, and over half of the major ones were previously unknown to the patient and their doctors.15Journal of Nuclear Medicine Technology. Incidental Findings on Myocardial Perfusion SPECT Images
These incidental findings range from benign lung nodules and degenerative spine changes to occasionally more serious discoveries like unsuspected masses or significant pleural effusions. Whether this is a benefit or an added worry depends on the finding. Clinically significant incidentalomas can lead to early treatment that might not have happened otherwise. On the other hand, benign-looking nodules may trigger follow-up imaging and anxiety. The key takeaway is that if your report mentions a non-cardiac finding, it is not necessarily alarming, but it deserves a conversation with your doctor about whether further evaluation is warranted.
Newer Camera Technology and What It Changes
For decades, SPECT cameras used large sodium iodide crystals with photomultiplier tubes to detect gamma rays. Over the last 10 to 15 years, a new generation of cameras built around cadmium-zinc-telluride (CZT) solid-state detectors has entered the market. These cameras are substantially more sensitive, meaning they can produce high-quality images with less tracer and in less time. A comparison of two such systems found that the choice of camera and its detector geometry can influence how scans are scored: one full-ring CZT system classified about 64 percent of patients as having normal perfusion, while a different fixed-angle CZT camera classified only about 29 percent of the same patients as normal.16MDPI. Comparative Analysis of Cardiac SPECT Myocardial Perfusion Imaging: Full-Ring Solid-State Detectors Versus Dedicated Cardiac Fixed-Angle Gamma Camera That discrepancy came from a small pilot study and did not reach statistical significance, but it highlights an underappreciated reality: the specific hardware your lab uses can affect what the images look like and how they are interpreted.
For you as a patient, the practical implication is that comparing scans performed at different facilities or on different camera types is not always straightforward. If your cardiologist wants to track changes in your perfusion over time, having repeat studies done at the same lab on the same equipment provides the most reliable comparison. The broader trend in the field, driven by these more efficient cameras, is toward lower radiation doses, shorter scan times, and potentially stress-only protocols that skip the rest images entirely when the stress scan is clearly normal.