Incomplete resolution of ST-segment elevation is a marker of transient microcirculatory dysfunction after stenting for acute myocardial infarction

Background - Incomplete ST-segment resolution (STR) after successful primary angioplasty for acute myocardial infarction ( AMI) is associated with a poor prognosis. We used intracoronary Doppler velocimetry to investigate whether incomplete STR after primary angioplasty is a marker of severe microcirculatory dysfunction. Methods and Results - Fifty patients with less than or equal to12-hour AMI underwent successful primary angioplasty and systematic stenting with a Doppler guidewire. Patients with incomplete (<50%) STR 60 minutes after TIMI 3 flow was restored had flow velocity features suggestive of severe microcirculatory dysfunction, including a higher incidence of early systolic retrograde flow (41% versus 9%, P = 0.007) and lower coronary flow velocity reserve (CVR, 1.3 versus 1.6, P < 0.001). CVR improved immediately after stenting in patients with greater than or equal to50% STR but not in patients with <50% STR. There was a significant correlation between STR and poststent CVR. At 3 months, CVR was similar in patients with <50% and greater than or equal to50% STR. However, left ventriculography indicated lower global (42% versus 55%, P = 0.001) and regional (16% versus 20%, P = 0.03) left ventricular ejection fractions and Tl-201 rest-redistribution scintigraphy indicated a larger infarct size (34% versus 16% Tl-201 defect, P = 0.007) in patients with <50% STR. Conclusions - After successful primary angioplasty with systematic stenting, <50% STR is a marker of severe albeit transient microcirculatory dysfunction in patients with AMI and is associated with more extensive myocardial damage.