MECHANISM AND SIGNIFICANCE OF PRECORDIAL ST-SEGMENT DEPRESSION DURINGINFERIOR WALL ACUTE MYOCARDIAL-INFARCTION ASSOCIATED WITH SEVERE NARROWING OF THE DOMINANT RIGHT CORONARY-ARTERY

The mechanism and significance of precordial ST depression during infe rior wall acute myocardial infarction (AMI) is debated. This study ass essed the location and extent of arterial perfusion distribution respo nsible for this electrocardiographic finding. Intracoronary thallium-2 01 was injected in 11 patients with 1-vessel right coronary disease to delineate perfusion distribution that was quantitated by a new angiog raphic distribution score. The angiographic score correlated with post erior (r = 0.84), posterolateral (r = 0.88) and total (r = 0.73) exten t of intracoronary thallium distribution. The angiographic distributio n score was related to electrocardiographic changes in 16 patients sho wing an inferior ST-segment elevation during angioplasty (7 with and 9 without precordial ST depression), of which 6 received intracoronary thallium injection. None had thallium distribution in the anterior or septal segment, but there was a trend toward a greater angiographic di stribution score and posterior segment thallium score in patients with precordial ST depression. In another 77 patients with inferior wall A MI due to right coronary occlusion (24 with concomitant left anterior descending narrowing), precordial ST depression was present in 16 with and 31 without left anterior descending narrowing (p = NS). The angio graphic distribution score was higher in those with than without preco rdial ST depression (0.59 +/- 0.10 vs 0.44 +/- 0.11, p <0.001) in both patients with and without left anterior descending disease. The magni tude of both inferior ST elevation and precordial ST depression correl ated with the angiographic distribution score, but only precordial ST depression was independently related in multivariate analysis. Precord ial ST depression during inferior wall AMI indicates a larger extent o f posterolateral and total perfusion of the infarct-related artery ind ependent of the presence or absence of left anterior descending narrow ing, and identifies a subgroup who may derive greater benefit from rep erfusion.