Infarct size measured by single photon emission computed tomographic imaging with Tc-99m-sestamibi - A measure of the efficacy of therapy in acute myocardial infarction

Background-Use of mortality as an end point in randomized trials of reperfu sion therapy requires increasingly large sample sizes to test advances comp ared with existing therapy, which is already highly effective. There has be en a growing interest in infarct size measurements by Tc-99m-sestamibi SPEC T(single photon emission computed tomographic) imaging as a surrogate end p oint. Methods and Results-We reviewed the reports published in English regarding infarct size measurements by Tc-99m-sestamibi. Four separate lines of publi shed evidence support the validity of SPECT imaging with 99mTc-sestamibi fo r determination of infarct size. This end point has been used in a total of 7 randomized trials-1 single center and 6 multicenter. The end point compa res favorably with left ventricular function and infarct size measurements with the use of other radiopharmaceuticals. The most important limitation o f this approach is the absence thus far of a randomized trial that has show n a corresponding decrease in mortality in association with a therapy that reduces infarct size. Conclusions-SPECT imaging with Tc-99m-sestamibi is the best available measu rement tool for infarct size. It has already served as an end point in earl y pilot studies to evaluate potential efficacy and in dose-ranging studies. It has the potential to serve as a surrogate end point to uncover advantag es of new therapies that may be equivalent to existing therapies with respe ct to early mortality.