We offer noninvasive tests to evaluate heart disease using a small amount of radioactive substance. It is injected into a vein and its presence is detected by a gamma camera. Images reveal areas of the heart that are not getting enough blood.
Among the techniques of nuclear cardiology, myocardial perfusion imaging is the most widely used.
Myocardial Perfusion Imaging
Myocardial perfusion images are combined with exercise to assess the blood flow to the heart muscle. Exercise can be in the form of walking on the treadmill or riding a stationary bicycle. A "chemical" stress test using the drug persantine or dobutamine may be performed in patients who are not able to exercise maximally, providing similar information about the heart's blood flow.
A small amount of an imaging agent - thallium or sestamibi (Cardiolite) or tetrofosmin (Myoview), is injected into the blood stream during rest and during exercise or chemical stress. A scanning device (gamma camera) is used to measure the uptake by the heart of the imaging material during (exercise or chemical stress) and at rest. If there is significant blockage of a coronary artery, the heart muscle may not get enough of a blood supply in the setting of exercise or during chemical stress. This decrease in blood flow will be detected by the images.
Myocardial perfusion studies can thus identify areas of the heart muscle that have an inadequate blood supply as well as the areas of heart muscle that are scarred from a heart attack. In addition to the localization of the coronary artery with atherosclerosis, myocardial perfusion studies quantify the extent of the heart muscle with a limited blood flow and can also provide information about the pumping function of the heart. Thus, it is superior to routine exercise stress testing and provides the necessary information to help identify which patients are at an increased risk for a heart attack and may be candidates for invasive procedures such as coronary angiography, angioplasty and heart surgery.
Positron Emission Tomography (PET)
PET is an imaging technique that produces a three-dimensional image of the body. These studies are noninvasive and are used to provide information about both the blood supply to the heart muscle and the metabolic activity of the heart. These studies can outline the heart muscle that is not getting adequate blood flow because of the blockage in the arteries of the heart. These studies can also show the heart muscle that has been scarred from past heart attacks, and also what has been damaged but has the potential to recover if a bypass surgery or an angioplasty is performed on the patient. This ability to distinguish irreversibly damaged heart muscle from damaged heart muscle with a potential to recover its function after bypass surgery or angioplasty is a major strength of PET imaging. PET studies can also be used to evaluate the nervous system of the heart. These studies can also help in making determinations about candidacy for bypass surgery or angioplasty. With the wider availability of PET imaging cameras, the use of PET imaging has increased significantly in the last few years.