26 Recent Advances in Nuclear Cardiology

Abstract: Nuclear cardiology uses radioisotopes to study various aspects of cardiac pathophysiology. Using the techniques of SPECT (Single Photon Emission Computed Tomography) and PET (Positron Emission Tomography) one can study myocardial function, perfusion, metabolism, receptors, infarction, atherosclerosis, apoptosis and success of gene therapy. Gated Blood Pool (GBP / MUGA) studies provide an accurate, reproducible and operator independent method for accurate estimation of left and right ventricular ejection fractions. Exercise MUGA/GBP studies provide a sensitive and specific tool for detecting myocardial ischemia and have excellent prognostic value. Myocardial perfusion scans performed with thallium, Tc-MIBI, tetrofosmin or with PET tracers like rubidium and ammonia, provide vital information on inducible myocardial ischemia. This information is important for making decisions about surgical versus medical management for coronary artery disease. Acute infarcts can be diagnosed in situations with equivocal ECG and cardiac enzyme findings at an early stage. The adrenergic innervation of the heart can be studied with 123I-MIBG and has prognostic value in heart failure and in predicting arrythmias. The heart uses fatty acids and glucose as its metabolic substrate. This utilization is altered in several disease states. PET scans are used to study cardiac metabolism in health and disease. Recent research is directed at imaging the unstable plaque with radiotracers. Apoptosis or programmed cell death can be studied with 99mTc-annexin V and is valuable in cardiac transplants in predicting rejection and in infarction. Finally, delivery and localization of stem cells can be followed with radionuclide techniques as also delivery and expression of therapeutic genes