Predicting chronic left ventricular dysfunction 90 days after ST-segment elevation myocardial infarction: An Assessment of Pexelizumab in Acute Myocardial Infarction (APEX-AMI) Substudy

Justin A Ezekowitz, Paul W Armstrong, Christopher B Granger, Pierre Theroux, Amanda Stebbins, Raymond J Kim, Manesh R Patel
American Heart Journal 2010, 160 (2): 272-8

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.

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