Disparate Impact of Ischemic Injury on Regional Wall Dysfunction in Acute Anterior vs Inferior Myocardial Infarction.

BACKGROUND: Acute transmural ischemia should induce similar magnitude of wall motion abnormality (WMA) in both anterior myocardial infarction (AMI) and inferior (IMI). However, patients with AMI generally suffer more severe hemodynamic compromise. METHODS: This retrospective study compared WMA's in ST segment elevation MI patients undergoing primary reperfusion and subsequent cardiac MRI. Regional systolic wall motion and thickening were assessed in all segments throughout the left ventricle (LV). RESULTS: We analyzed 37 patients (AMI = 24 vs IMI = 13). Reperfusion success was achieved in all and there were no differences between groups in door-to-balloon time (AMI median 77 vs IMI 119 min, p = 0.085). Compared to IMI, in AMI LV ejection fraction was more depressed (37 ±â€¯7.6% vs 51 ±â€¯10.3%, P = 0.0006) and regional WMA more severe (total regional WMA score = 2.63 ±â€¯0.53 vs IMI = 2.1 ±â€¯0.52, P = 0.007). Regional dyskinesis was commonly observed in AMI patients but was rare in IMI (79% vs 7% of cases). Similarly, AMI manifested systolic thinning, whereas thickening was depressed but still present in IMI patients. Strikingly, WMA severity differed downstream relative to the origin of the infarct artery: In all AMI cases, WMA worsened from proximal anterior toward the distal apical zone; in IMI the pattern was reverse, with WMA consistently most severe in the basal segment of the inferior-posterior wall with preservation toward the apical distribution of the infarct vessel. CONCLUSION: These results demonstrate a disparate impact of ischemic injury on mechanical performance of the anterior vs inferior-posterior walls. These findings may be attributable to differences between the walls in architecture, mechanics and coronary blood flow. These observations may have implications for myocardial salvage, remodeling and prognosis.