Abstract 16739: Regional Variation in the Relationship of Infarct Size to Left Ventricular Ejection Fraction: Implications for Risk Stratification for Sudden Cardiac Death
Introduction: In patients with coronary artery disease (CAD), guidelines for primary prevention of sudden cardiac death (SCD) use left ventricular ejection fraction (LVEF) ≤35%. The substrate for SCD is myocardial infarction (MI); indeed, MI size expressed as percent of LV mass (IM%) measured by cardiac magnetic resonance imaging (CMR) has been shown to be a better predictor of inducible ventricular tachycardia (VT) on electrophysiologic study than LVEF, with a cutoff of > 10% providing the highest sensitivity.
Purpose: To examine the influence of MI location on the relationship between IM% and LVEF.
Methods: We analyzed cine and late gadolinium enhanced (LGE) CMR images for 412 patients with CAD (81% male, age 62.3 ± 11.4) and a history of MI from the DEfibrillators To REduce Risk by MagnetIc ResoNance Imaging Evaluation Trial (DETERMINE trial, www.clinicaltrials.gov). LVEF and IM% were quantified (Medis QMass MR 7.2). We performed segmental visual scoring of cine (from 0 = normal to 4 = dyskinesis) and LGE images (from 0 = none to 4 = 76-100%). Each of the 17 segments was assigned to a coronary artery territory based on American Heart Association segmentation recommendations. MI location was calculated as the territory with the highest LGE score: left anterior descending (LAD), left circumflex (LCX), and right coronary artery (RCA).
Results: Overall, 206/412 (50%) of patients had IM% > 10% while maintaining LVEF > 35%. The distribution of MI location was LAD (205), LCX (84), and RCA (123). The impact of increasing IM% on LVEF differed based on MI location (figure). The expected IM% required to reduce LVEF to 35% for a LCX MI was 19%, for LAD was 26%, and for RCA was 34%.
Conclusions: As a marker of MI burden, LVEF is insensitive and is strongly influenced by MI location. As it best represents the substrate for SCD and is related to both mortality and inducible VT, further efforts are required to investigate IM% as a predictor of SCD, independent of LVEF.
- © 2011 by American Heart Association, Inc.