[Infarct size related to the distribution and site of coronary artery lesions studied by the unfolded map technique using single photon emission computed tomography]

To assess the relative importance of the anatomical characteristics of the coronary artery distribution and the sites of the arterial stenoses in relation to infarct size, 21 patients with old myocardial infarction and angiographically-proven 90% or greater stenoses (AHA classification) of one of the major coronary arteries were studied. The infarct size was evaluated by a new quantitative method, the unfolded map, derived from single photon emission computed tomography (SPECT). Eleven patients had right coronary artery disease (Group RCA: segment 1; five patients and segment 2; six patients). Seven patients who had the large left anterior descending artery (LAD) which was distributed to the inferior portion of the apical area were defined as Small R, and four patients with large RCA as Large R. Ten patients each had a significant stenosis in the LAD (Group LAD: segment 6; six patients and segment 7; four patients). Four patients with significant stenosis proximal to segment 9 were defined as Pre-9, and seven patients with stenosis distal to the segment, as Post-9. Stress T1-201 scintigraphy with SPECT was performed and the unfolded map was obtained with data of the maximal count circumferential profiles in the redistribution image. Infarction was defined as a defect below 55% of the standard value. The necrotic area ratio expressed as percentage of the defect area to the entire map area was calculated and used as the indicator of infarct size. Although there was no significant difference in the necrotic area ratio between segment 1 and 2 lesions. Large R had the significantly larger necrotic area ratios (24.9 +- 4.6%) than did Small R (9.7 +- 4.4%; p less than 0.01). In the Group LAD, there was no significant difference in the necrotic area ratio between segment 6 and 7 lesions, but Pre-9 had the larger ratio (30.4 +- 3.3%) than did Post-9 (15.4 +- 7.7%; p less than 0.01). These data suggest that the factors related to infarct size are either the distribution of the coronary arteries in the apical area in the Group RCA or the sites of the stenotic lesions relative to the branching portion of the first diagonal branch in the Group LAD.