Predicting chronic left ventricular dysfunction 90 days after ST-segment elevation myocardial infarction: An Assessment of Pexelizumab in Acute Myocardial Infarction (APEX-AMI) Substudy.
OBJECTIVES
The purpose of this study was to determine predictors of 90-day left ventricular function following acute ST-segment elevation myocardial infarction (STEMI) using variables from clinical presentation, biomarker testing, and cardiovascular magnetic resonance imaging (CMR).


BACKGROUND
Identifying patients with acute STEMI who experience adverse remodeling and develop left ventricular dysfunction 3 months post-MI is a priority for guiding subsequent therapy.


METHODS
The Assessment of Pexelizumab in Acute Myocardial Infarction trial tested pexelizumab treatment in STEMI patients presenting within 6 hours of symptom onset who were to undergo primary percutaneous coronary intervention. We studied 64 patients within this trial according to a prespecified substudy that included paired core laboratory delayed-enhancement CMR at days 3 and 90 as well as plasma N-terminal pro-B-type natriuretic peptide (NT-proBNP; in picograms per milliliter) measured at randomization and 24 hours. 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 (52-68), 89% were male, and 60% had anterior STEMI. Time from symptom onset to percutaneous coronary intervention was 3 hours. The median baseline LVEF was 48% (38%-56%) and was 50% (40%-54%) at 90 days: 7 patients (11%) had an LVEF <35% at 90 days. Patients with a lower 90-day LVEF (as a continuous variable) had a higher 24-hour NT-proBNP (P = .02) and a larger baseline infarct size by CMR (median 15% LV [8%-20% LV]) (P < .01). Microvascular obstruction (no reflow) was greater as measured by CMR (median 2.8% [1.4%-6.1%]) in patients with a lower 90-day LVEF (P < .01). Median baseline and 24-hour NT-proBNP levels were 94 pg/mL (54-292 pg/mL) and 1,448 pg/mL (958-2,599 pg/mL), respectively. In a multivariable model with clinical, biomarker, and imaging variables, only 3 variables independently predicted 90-day LVEF: 24-hour NT-proBNP, baseline CMR infarct size, and microvascular obstruction.


CONCLUSIONS
Three key pathophysiologic variables of the post-STEMI myocardium measuring baseline infarct size and the extent of microvascular obstruction on CMR and wall tension (24-hour NT-proBNP) independently predicted 90-day LVEF. Further studies linking these measures with earlier use of clinical therapies may be warranted.