Time-dependency of edema-based assessment of area-at-risk in reperfused acute myocardial infarction

Methods Cardiac MR was used to investigate the development and persistence of edema volume increases in the acute postinfarct period using both T2-weighted STIR imaging and T2 maps. LAD instrumented canines (n=9) underwent three hours of no-flow ischemia followed by reperfusion and were studied [using Siemens 1.5 T Espree scanner] at five time points (before and during ischemia and 2, 5, 7 and 56 days post-reperfusion). Scan parameters for T2-STIR acquisitions were: TE=64ms, TR=2-3 R-R intervals, resolution=0.9x0.9x8.0mm 3 .T 2 maps were computed from multiple T2-prepared acquisitions with different preparation times (0, 24, and 55 ms) with spatial-resolution of 1.0x1.0x8.0mm 3 . Late-enhancement imaging confirmed LAD infarction. Areas of interest were determined as follows: For T2 maps - region with T2 values greater than 2SD from remote territories; and for T2-STIR images- regions exceeding 2SD of the signal intensity of the remote regions. Edema volume was computed as highlighted areas multiplied by imaging slice thickness. Percent volume of edema was computed relative to total myocardial volume. Results are reported as mean ± SEM for each time point. Results Percent volume of edema (Area-At-Risk) - T2 Maps: Pre-ischemia: 0.8±0.4%; Ischemia: 2.5±1.4%; Day 2: 18.3