BACKGROUND Protection of distal embolization by balloon occlusion and thrombus aspiration has not improved microvascular circulation nor decreased myocardial injury during primary percutaneous intervention (PCI) for ST-elevation myocardial infarction (STEMI) in randomized trials. In a prospective randomized trial, we investigated the mechanism of the poor effect of distal protection and thrombus aspiration (DP-TA) in 126 patients with STEMI.

METHODS Patients with first-diagnosed STEMI were randomly assigned to DP-TA pretreatment or conventional PCI (c-PCI). Primary endpoint was reduced left ventricular end-diastolic volume (LVEDV) measured by MRI at post-PCI and 6 months after PCI. Secondary end points were infarct ratio (infarct size to entire LV size) by delayed enhancement (DE), area at risk (AAR) ratio (AAR to entire LV size) by T2 high signal, microvascular occlusion index (MVO) ratio (MVO to entire LV size) by DE, and myocardial salvage index (MSI: (AAR--infarct size)*100/AAR) using cardiac magnetic resonance imaging (MRI) within 3 days after PCI.

RESULTS Baseline characteristics of the patients including cardiovascular risk factors and lesion characteristics were similar between the two groups. DT-PA failed to improve LV remodeling at 6 months (LVEDV 140 ± 39 vs 133 ± 37 in c-PCI group, p=0.418). Infarct ratio, AAR ratio and MSI were not statistically different between DP-TA group and c-PCI group. However, MVO ratio was significantly larger in DP-TA group than in c-PCI group (2.4 ± 2.7 vs 1.1 ± 1.9, p=0.045).

CONCLUSION DP-TA was potentially hazardous in primary PCI for STEMI by increasing MVO. DP-TA should not be used in STEMI.