Abstract 3567: Early Prediction of Left Ventricular Ejection Fraction 90 Days After STEMI Using NT-proBNP and Cardiac Magnetic Resonance Imaging
Background Identifying patients with acute ST-segment Elevation Myocardial Infarction (STEMI) who will develop a persistently low ejection fraction three months post-MI is clinically relevant for both medical and invasive therapies.
Methods The Assessment of Pexelizumab in Acute Myocardial Infarction (APEX-AMI) trial tested pexelizumab treatment in STEMI patients presenting within 6 hours of symptom onset who were to undergo primary PCI. We studied 64 patients in a pre-specified substudy who had paired core-lab biomarkers and delayed enhancement cardiac magnetic resonance imaging (CMR) at days 3 and 90, as well as NT-proBNP (pg/ml) measured at randomization and 24 hours. All continuous factors were modeled linearly or with transformations. Values are medians (25th and 75th centiles) unless otherwise stated. A multivariable model predicting day 90 left ventricular ejection fraction (LVEF) was developed from clinical, biomarker and imaging findings.
Results Patients had a median age of 60 years (52 to 68), 89% were male and 60% had anterior STEMI. Time from symptom onset to PCI was 3 hrs. The median baseline LVEF was 48% (38 to 56%), and was 50% (40 to 54%) at 90 days. Only 7 patients (11%) had a LVEF <35% at 90 days. Median baseline and 24 hour NT-proBNP levels were 94 pg/ml (54 to 292) and 1448 pg/ml (958 to 2599), respectively. Patients with a lower 90dLVEF had a higher 24 hour NT-proBNP (p=0.02). Baseline infarct size by CMR (median 15% LV [8 to 20% LV]) was larger in patients with a lower 90dLVEF (p<0.01). Microvascular obstruction as measured by CMR (median 2.8% (1.4 to 6.1%) was larger in patients with a lower 90dLVEF (p<0.01). In the multivariable model with clinical, biomarker, and imaging variables, only 3 variables independently predicted 90dLVEF: 24 hour NT-proBNP, baseline CMR infarct size and microvascular obstruction.
Conclusions Variables representing three physiologic aspects of the post-STEMI myocardium: the baseline infarct size (by CMR), the degree of microvascular obstruction (no reflow), and wall tension (24-hour NT-proBNP) independently predict the 90-day left ventricular ejection fraction. Integration of these measures into clinical practice is warranted.