Nuclear Cardiology

Myocardial Perfusion Imaging

The main clinical examination performed in Nuclear Cardiology is myocardial perfusion imaging. This technique involves small doses of radioisotopes injected intravenously, either during exercise or after stimulation of the blood flow to the heart. This results in uptake of the radioisotope in part of the heart receiving normal blood flow. Areas which are supplied only by blocked blood vessels will show less uptake of the radioisotope, and are seen as “holes” in the subsequent pictures of the heart, which are displayed in complete 3-dimensional format, such as in a computerized tomographic scan using x-rays.

This technique also has the advantage of giving an assessment of the volume of the total heart, which is not obtaining adequate blood supply. The larger the volume of the heart not receiving adequate blood, the more dangerous the situation is for the patient if this decreased blood flow is not corrected. By closely tracking the position of the heart muscle during different phases of the cardiac cycle, one is able to display in real time the squeezing action of the heart and calculate the percentage of blood being ejected from the heart with each beat. This number, called the ejection fraction, is an important descriptor of overall heart function in an individual patient.

Comfortable Testing

At the Cardiovascular Center of Excellence, a new reclining chair is in place for patient comfort. This new development also decreases the interference of soft tissue underlying the patient’s diaphragm, from interfering with test interpretation.

Results

If the myocardial perfusion scan is normal, generally speaking, it is safe for the patient to be treated only with medicines with no further invasive cardiac workup for blockages required.

MUGA

A gated radionuclide ventriculargram [MUGA] is used to assess the patient’s ejection fraction when information on blood flow to the heart muscle is not required. In this test, the patient’s red blood cells are labeled with the radioisotope, and the motion of the blood pool as the heart moves is recorded. This test is used to check for changes in the ejection fraction over time, and for close assessment of the rapidity of cardiac filling.