Application of technetium-99m sestamibi single photon emission computed tomography in acute myocardial infarction: measuring the efficacy of therapy.

Infarct size and myocardial salvage measured by technetium (Tc)99m sestamibi single photon emission computed tomography (SPECT) imaging have been applied as surrogate endpoints in clinical trials of acute myocardial infarction (MI). The major advantage of these end-points over mortality is the ability to use much smaller sample sizes to compare different treatment strategies in acute MI. Multiple categories of evidence validate SPECT infarct size and myocardial salvage as surrogate endpoints, including: association with other variables used to measure infarct size; association with markers of myocardial perfusion; identification of myocardial fibrosis in pathology specimens; prediction of improvement in dysfunctional myocardial segments following revascularization; correlation between infarct size and mortality; and, demonstration that therapies which result in smaller infarct size also result in better clinical outcome in the same patients. These SPECT endpoints have been applied in over 30 clinical acute MI trials. Approximately one-third of these trials reported positive results in the intervention group or a subset of the intervention group. SPECT infarct size and myocardial salvage are the most extensively validated and widely applied surrogate endpoints in the setting of acute MI.