Intercenter variability in outcome for patients treated with direct coronary angioplasty during acute myocardial infarction

Direct coronary angioplasty is an effective therapy for acute myocardial infarction, but its success may be dependent on both ready availability and operator skill. The purpose of this study was to investigate the impact of the center performing direct coronary angioplasty for acute myocardial infarction while controlling for parameters known to affect outcome.

The study group consisted of 99 patients with ST elevation who were treated with direct angioplasty in four high-volume centers. Patients were injected with technetium-99m sestamibi intravenously and then taken to the cardiac catheterization laboratory. Antegrade flow was graded before and after direct coronary angioplasty. Single photon emission computed tomography was performed 1 to 6 hours after injection to measure myocardium at risk and residual blood flow to the jeopardized zone using previously published quantitative methods. A repeat sestamibi injection and tomographic acquisition were performed at hospital discharge to measure actual infarct size. There were no significant differences by center for baseline clinical characteristics, mean myocardium at risk (29% to 37% left ventricle [LV]), time to reperfusion (3.1 to 4.1 hours), residual blood flow, infarct location, or antegrade flow. Despite these similarities, there were differences in outcome measures by center. Mean infarct size was as follows: center 1, 15%; center 2, 12%; center 3, 10%, center 4, 23% (all LV; p = 0.11 ). Mean left ventricular ejection fraction at discharge also demonstrated significant differences: center 1, 0.57; center 2, 0.47; center 3, 0.53; center 4, 0.47 (p = 0.002). The prevalence of Thrombolysis in Myocardial Infarction grade 3 flow after angioplasty significantly differed by center: center 1, 92%; center 2, 94%; center 3, 87%; center 4, 71 %; (p = 0.01). There was a low mortality rate for all four centers ranging from 0% to 6%. After adjustment for myocardium at risk, residual blood flow, and time to reperfusion, the primary outcome of the center where the angioplasty was performed was an independent determinant of both infarct size and left ventricular ejection fraction.

The success of direct coronary angioplasty in reducing infarct size and preserving left ventricular function depends on the center performing the procedure. Direct measurement of the effectiveness of this reperfusion modality in community practice is required to assess the impact of this effect.