The present role of nuclear cardiology in clinical practice.

Many advances have been made in the field of nuclear cardiology in the past decade for enhancing the diagnostic and prognostic value of stress myocardial perfusion imaging and the assessment of myocardial viability using SPECT technology. Gated SPECT for determining regional and global function have provided incremental diagnostic and prognostic information in the evaluation of patients with suspected or known coronary artery disease. Left ventricular ejection fraction and regional myocardial wall thickening can now be simultaneously evaluated with regional perfusion particularly with the use of the (99m)Tc-labeled perfusion agents such as sestamibi and tetrofosmin. Many studies have shown that the extent and severity of stress-induced perfusion defects have incremental prognostic value over exercise electrocardiographic stress test variables alone. Patients with normal perfusion scans have <1% combined cardiac death and myocardial infarction rates per year and thus have an excellent prognosis. Diabetics are particularly benefited from stress perfusion imaging for detection of coronary artery disease and risk assessment. Diabetics have a worse prognosis than nondiabetics for the same amount of hypoperfusion on stress SPECT studies. Quantitative rest perfusion imaging with (201)Tl or with one of the (99m)Tc-labeled imaging agents, or PET imaging with (18)F-deoxyglucose can accurately distinguish viable from irreversibly injured myocardium providing useful information for identifying which patients with ischemic cardiomyopathy benefit most from coronary revascularization with a subsequent improvement in left ventricular function and enhanced survival. Finally, serial stress perfusion imaging can be employed to monitor the efficacy of medical therapy that improves endothelial function and myocardial blood flow reserve.