Abstract 1972: ST Segment Resolution After Reperfusion Therapy for Acute Myocardial Infarction is Related to Microvascular Obstruction
Introduction: Incomplete ST segment resolution (STR) after reperfusion therapy in ST elevation myocardial infarction (STEMI) is related to increased mortality. Subendocardial hypoenhancement within a region of hyperenhancement on cardiovascular magnetic resonance imaging (CMR) has been shown to represent microvascular obstruction (MVO). We prospectively analyzed the relation of STR with this CMR finding.
Methods: In 25 first STEMI patients (pts) who underwent primary angioplasty (PCI), digital 24-hour 12-lead Holter registration was started immediately after admission and before PCI. ST segment deviation was measured 60 ms after the J-point. STR was calculated from the lead showing maximum ST deviation before PCI and expressed as percent decrease 30 minutes after first balloon inflation. CMR was performed 5 ± 2 days after admission. Ten minutes after Gadolinium injection and with adjusted inversion times, a 3D T1 weighted inversion-recovery gradient echo technique was used to assess microvascular integrity. Subendocardial hypoenhanced areas within a region of hyperenhancement were identified as MVO. Total area of hyper- and hypoenhancement were expressed as percentage of total left ventricular (LV) mass after manual planimetry. CMR and ECG analyses were done by blinded observers.
Results: Mean age was 56 ± 11 years, 23 pts were male, 7 pts had anterior wall infarctions. Median occlusion time was 222 minutes (IQR 156–309). MVO was detected in 12 pts (48%). The MVO to LV mass ratio was 2.0 ± 1.3 %. Pts with MVO had larger regions of hyperenhancement (22.4 ± 10 % vs. 5.5 ± 5.5 %; p < 0.001), total CK release (AUC 69998 ± 27476 vs. 21041 ± 14841; p = 0.002) and lower LV ejection fraction (48.7 ± 6.1 % vs. 55.9 ± 4.2; p = 0.002), all indicating larger infarctions. Mean STR in patients with and without MVO was 66.8 ± 25.6 % and 89.9 ± 13.9 % (p = 0.002). MVO and STR showed an inverse relation of −0.57 (p = 0.003) using Spearman’s correlation coefficient.
Conclusion: We found that STR is inversely related to MVO as assessed by CMR. This suggests STR to be a good reflection of microvascular status 30 minutes after mechanical reperfusion in pts with STEMI.