Myocardial Perfusion Imaging
Normal cardiac function at rest and during exercise depends upon adequate blood supply to the heart muscle. Blood is supplied to the heart’s pumping chambers, or ventricles, by the coronary arteries. The human heart has three major coronary arteries that supply blood to the ventricles. Disease in one or more of the coronary arteries may result in poor blood supply, or “perfusion”, to that region of the heart. Areas of poor perfusion can be visualized by nuclear perfusion imaging. Myocardial perfusion imaging is an excellent diagnostic tool for patients with concerning symptoms either at rest or with exertion.
During myocardial perfusion imaging, an imaging agent, or “isotope”, is injected into a vein, the nuclear camera collects the radioactivity emitted by the isotope, and computerized images of the heart and blood flow are created. An initial set of images is obtained at rest. Patients then exercise on a treadmill, during which vital signs and electrocardiograms are monitored continuously by one of our cardiologists. Towards the end of the exercise protocol, a second injection is performed and a series of cardiac images are obtained after exercise. By comparing the resting and exercise images side-by-side, areas of reduced perfusion can be identified. Nuclear imaging also allows us to assess overall cardiac pump function and to evaluate regional areas of reduced pump function that correspond to reduced perfusion.
For patients who are unable to perform exercise on a treadmill, myocardial perfusion imaging is accomplished with the assistance of intravenous medication. Most commonly, the medication “adenosine” is used. Adenosine is a naturally occurring substance that affects blood flow through the heart arteries. The typical duration of an adenosine infusion used to perform a stress test is four minutes. Adenosine has an extremely short half-life, which means that the body metabolizes and eliminates the drug with no lasting effects in just a few moments after the test is completed.
All of our cardiologists are board-certified to perform exercise and pharmacologic stress tests. Our cardiologists with additional board certification in the field of nuclear cardiology will interpret the images and discuss the results directly with your personal cardiologist. Myocardial perfusion stress test results, and any further diagnostic and treatment recommendations, such as cardiac catheterization, are usually communicated to patients within 24 hours.