Assessment of myocardium at risk in pigs with single photon emission computed tomography and computerized vectorcardiography during transient coronary occlusion

Since myocardium at risk (MAR) is the major prognosticator of final infarct size and outcome in patients with acute myocardial infarction, it is highl y desirable to estimate the size of the acutely ischemic myocardium. that i s the MAR, in these patients. We assessed MAR size by Tc-99m-sestamibi-SPEC T and computerized vectorcardiography using autoradiography as reference me thod. Transient myocardial ischemia was achieved in 12 pigs by coronary art ery occlusion with PTCA catheters. During the procedure, computerized vecto rcardiography was continuously recorded. After injection of Tc-99m-sestamib i and gadolinium-153-labelled microspheres, MAR size was estimated by SPECT and post-mortem autoradiography. Different cut-off levels (50-70%) were co mpared with respect to MAR-SPECT. Tc-99m-sestamibi-SPECT showed a good corr elation with autoradiography (r = 0.94). Computerized vectorcardiography sh owed a good correlation with autoradiography as well as with Tc-99m-sestami bi-SPECT (STC-VM: r= 0.75 and 0.80, respectively, ST-VM: 0.75 and 0.87, res pectively). It was found that 1) MAR assessed by Tc-99m-sestamibi-SPECT cor relates closely with the autoradiographic reference 2;) a lower cut-off poi nt of 60%, of maximum uptake for MAR by Tc-99m sestamibi-SPECT gives the cl osest correlation with the autoradiographic reference. and 3) ST-VM and STC -VM correlate well with MAR assessed by Tc-99m-sestamibi-SPECT and autoradi ography.