Nuclear Cardiology and Stress Testing
Nuclear cardiology studies use noninvasive techniques to assess myocardial blood flow, evaluate the pumping function of the heart as well as visualize the size and location of a heart attack. 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 is most often in the form of walking on the treadmill. A "chemical" of "pharmacological" stress test using the drug dipyridamole, adenosine or dobutamine is 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 sestamibi (Cardiolite), tetrofosmin (Myoview) or Thallium, 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 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 and may be candidates for invasive procedures such as coronary angiography, angioplasty or heart surgery.
Evaluation of Cardiac Function with Radionuclide Ventriculography
Radionuclide ventriculography (gated blood pool study) is a noninvasive study, which provides information about the pumping function of the heart. In patients with coronary artery disease, and in those who have had a heart attack, the assessment of the pumping function of the heart (also known as the ejection fraction) is essential in the prediction of both long term and short-term survival. A small dose of an imaging agent is injected into the blood stream and pictures of the four chambers of the heart are taken using a special camera (gamma camera).
Assessment of Myocardial Injury, Infarction and Infection
The basic cellular component of the heart muscle may be irreversibly affected in the setting of a limited blood supply and or inflammation. Nuclear cardiology techniques can be used to determine which areas of the heart muscle have been damaged by infection or by a heart attack. These techniques can also be used to monitor the status of the heart muscle in the patient after cardiac transplantation.
For a more detailed description of the different Nuclear Cardiology tests, please go to www.asnc.org and click PATIENTS.
The Mount Sinai Nuclear Cardiology Laboratory was opened in 1991 and currently performs close to 5,000 tests a year. Imaging studies are performed on dual head SPECT cameras, all equipped with attenuation correction hardware. The Laboratory is ICANL certified. All Attendings in Nuclear Cardiology are Board certified in Internal Medicine, Cardiovascular Diseases and Nuclear Cardiology. Technical personnel include experienced Registered Nurses and Certified Nuclear Technologists. All Laboratory employees are BLS (Basic Life Support) or ALS (Advanced Life Support) certified.
We perform all forms of cardiovascular stressing: Exercise, pharmacological stress (IV adenosine, IV dipyridamole, IV dobutamine). Perfusion tracers (Tc99m sestamibi, Tc99m tetrofosmine and Tl-201) are utilize according to the appropriate indication for individual patients. Gated blood pool studies (MUGA), both at rest and during bicycle exercise are offered to patients who need evaluation of land and/or right ventricular function.
Recently, we started performing cardiopulmonary stress testing (with measurement of oxygen consumption and cardiac output during exercise using inert gas rebreathing method). This testing is most appropriate for patients with advanced congestive heart failure.
The Laboratory also offers microvolt T- wave alternans testing. The method is used to assess risk of sudden death. For more information, please go to www.cambridgeheart.com and click PATIENTS.
For the past decade, the Laboratory has participated in numerous multicenter Clinical Trials. The most recent trials have evaluated new indications for SPECT imaging (INSPIRE, VGEF), new types of pharmacological stressors (CVT) and new tracers for cardiac neuroimaging in patients with end stage heart failure (MIBG) and ischemia imaging in patients presenting to the Emergency Department with new onset of chest pain (MIP – BP 22 and MIP – BP 23).