New agents and techniques in the assessment of myocardial perfusion and function:

Major advances in perfusion and function imaging of the heart have occurred during the past decade. These include the availability of the new Tc-99m-labeled tracers, hexakis-2-methoxyisobutyl-isonitrile and teboroxime, with ideal energy for gamma camera imaging, more optimal dosimetry than Tl-201, and the potential for simultaneous function and perfusion imaging. The new agents also allow performance of dual isotope protocols combining two tracers and exploiting the ability of the gamma camera to differentiate gamma energies. The minimal redistribution of hexakis-2-methoxyisobutyl-isonitrile has been exploited by investigators to assess myocardial salvage following reperfusion for myocardial infarction. Tl-201 continues to have widespread use, and recent studies have extended its value in the assessment of viability when used with the appropriate protocol. In addition to dipyridamole, the new pharmacologic stress agents, adenosine and dobutamine, have also been shown to be safe and efficacious for patients unable to exercise. Radio-labeled antimyosin antibodies have been investigated for their potential in infarct-avid imaging and transplant rejection. Positron emission tomography, with the ability to perform attenuation correction and quantitation, has had increasing acceptance in the clinical arena.