Effects of primary angioplasty for acute myocardial infarction on early and late infarct size and left ventricular wall characteristics

OBJECTIVES: We aimed to study the effects of early successful primary angioplasty for ST-segment elevation acute myocardial infarction (AMI) on early and late infarct size and left ventricular (LV) wall characteristics. BACKGROUND: Early reperfusion treatment for AMI preserves LV function, but the effects on early and late infarct size, end-diastolic wall thickness (EDWT), and segmental wall thickening (SWT) are not well known. METHODS: In 22 patients with successful primary angioplasty for first AMI, cine-magnetic resonance imaging (MRI), first-pass perfusion, and delayed-enhancement imaging was performed at five days and five months. The extent of microvascular obstruction (MO) was evaluated on perfusion images. Infarct shrinkage was defined as the difference between the volume of delayed-enhancement at five days and five months. The EDWT and SWT were quantified on cine-MRI. RESULTS: Infarct shrinkage occurred to the same extent in small and large infarctions [r = 0.92; p < 0.001], with a mean decrease of 31% (35 ± 21 g to 24 ± 17 g). Dysfunctional segments without MO had an increased EDWT at five days compared with remote myocardium (9.2 ± 1.7 mm vs. 8.4 ± 1.7 mm; p < 0.001). At five months, EDWT in these segments became comparable to the thickness of remote myocardium (7.8 ± 1.6 mm vs. 7.6 ± 1.4 mm; p = 0.60), and SWT improved (21 ± 15% to 40 ± 24%; p < 0.001) but remained impaired (40 ± 24% vs. 71 ± 29%; p < 0.001). Segments with MO demonstrated wall thinning at five months (6.4 ± 1.3 mm vs. 7.6 ± 1.4 mm; p = 0.006) and no significant recovery in SWT (12 ± 14% to 17 ± 20%; p = 0.15). CONCLUSIONS: Infarct size decreased by 31%. Segments without MO had early increased wall thickness and late partial functional recovery. Segments with MO showed late wall thinning and no functional recovery at five months.