Area at risk and collateral circulation in a first acute myocardial infarction with occluded culprit artery. STEMI vs non-STEMI patients.

BACKGROUND: It is unclear why among patients with first acute myocardial infarction and an occluded culprit artery only some present ST segment elevation. In fact, there is no study that compares the angiographic area at risk and the collateral circulation in first NSTEMI vs STEMI patients.

METHODS AND RESULTS: 205 patients admitted for myocardial infarction with occluded culprit artery were included, 132 STEMI and 73 NSTEMI. Demographic data, the area at risk determined by the BARI score and collateral supply by the Rentrop score from the 2 groups were compared. NSTEMI patients showed lower peak Tn I than STEMI in the overall group but also in the 3 subsets with different culprit arteries (p < .001). They also presented a higher rate of left circumflex coronary artery (CFX) as culprit artery (52% vs 14%, p < .001), smaller BARI score area of the culprit artery (5.4 vs 7.6, p < .001), and higher frequency of well-developed collaterals (Rentrop score ≥ 2, 1.82 vs 0.41, p < .001). The latter was also higher in each of the 3 different culprit arteries (p = .002-<0.001) Among 38 NSTEMI patients with CFX occlusion, 20 with ≥1 mm ST depression in V2 to V4 (possible posterior infarction) showed a similar Rentrop score than the 18 with other ECG changes but lower Tn I peak (p = .012).

CONCLUSIONS: In first acute myocardial infarction with an occluded culprit artery NSTEMI patients - including those with possible posterior infarction - present smaller infarct size and higher collateral blood supply than STEMI patients in each of the 3 main culprit arteries.