Abstract 1749: Structural Abnormalities and Functional Implications of Predischarge ST-Segment Elevation after Acute Myocardial Infarction
Background persistence of ST-segment elevation (STE) lasting for a long time after ST-segment elevation myocardial infarction has been ascribed to left ventricular aneurysm. However, its pathological basis is still lacking. We sought to evaluate myocardial structural abnormalities and underlying predischarge STE, using contrast-enhanced magnetic resonance (ce-MR).
Methods: 40 patients underwent direct angioplasty for first acute STEMI of the anterior myocardial wall were studied by ce-MR. Predischarge STE was defined by ≥ 2 mm STE in two or more leads on pre-discharge electrocardiogram. At ce-MRI, the presence and extent of myocardial necrosis (late hyperenhancement) and persistent microvascular obstruction (PMO) (late hypoenhancement), as well as wall motion abnormalities were assessed on a 17-segment model. Myocardial necrosis was labelled as transmural if late-hyperenhancement extended to > 75% of the thickness of at least 2 contiguous segments.
Results: Patients with predischarge STE had larger risk area as assessed by sum of ST elevation and number of leads showing ST elevation at baseline (p = 0.01), and showed a trend toward longer pain-to-balloon time (p = 0.06), and less TIMI flow after intervention (92.9% vs 45.5%, p = 0.003). At ce-MRI, patients with predischarge STE had more often transmural necrosis and PMO than patients without STE (90.0% vs 55.2%, p = 0.03; 81.8% vs 44.8%, p = 0.002, respectively). Left ventricular aneurysm was seen in 40.0% of patients with STE and in 14.3 patients without STE (p = 0.08). Furthermore in patients with STE, transmural necrosis involved 5.4 ± 2.4 myocardial segments vs 3.06 ± 2.87 segments in patients without STE (p = 0.20); PMO involved 3.45 ± 2.80 myocardial segments in patients with STE and 0.93 ± 1.51 in patients without STE. In a multivariate model the extent of PMO was the only independent predictor of predischarge STE (OR 2.39, CI 1.28 – 4.48, p = 0.006).
Conclusions: Predischarge ST-segment elevation after myocardial infarction is related to a larger extent of transmural necrosis and persistent microvascular damage as assessed by ce-MR. However, the extent of microvascular damage is an independent determinants of predischarge ST segment elevation.