Abstract 515: Mechanical Dyssynchrony Measured by Gated Single Photon Emission Computed Tomography Phase Analysis Predicts Ventricular Remodeling After Acute ST-Elevation Myocardial Infarction
Background: Left ventricular dyssynchrony is an adverse consequence of ST elevation myocardial infarction (STEMI) and bears an unfavorable prognosis. Mechanical dyssynchrony as measured by phase analysis from gated single photon emission computed tomography (GSPECT) correlates well with other imaging methods of assessing dyssynchrony but has not been studied in STEMI. We hypothesized that dyssynchrony as measured by GSPECT would predict adverse remodeling after STEMI.
Methods: In 28 subjects suffering STEMI, GSPECT with technicium-99m sestamibi was performed immediately after presentation (day 5) and remotely (6 months). Parameters of left ventricular dyssynchrony (QRS width, histogram bandwidth [HBW] and phase standard deviation [PSD]) were measured from GSPECT using the Emory Cardiac Toolbox. Left ventricular volumes, ejection fraction (LVEF) and infarct size were also assessed.
Results: After successful primary percutaneous coronary intervention to the infarct-related artery, subjects had an LVEF of 46.4±11% and a resting perfusion defect of 27.4±16% at baseline. Baseline QRS width was normal (91.5 ±17.5 msec). Subjects with STEMI had dyssynchrony compared with a cohort of 22 normal subjects (age 57.2±10.6 years, <5% perfusion defect) by both HBW (100.3±70.7 versus 26.5±5.3 degrees, p<0.0001) and PSD (35.3±16.9 versus 7.9±2.1 degrees, p<0.0001). Baseline HBW correlated with resting perfusion defect size (r=0.67, p<0.001), end-systolic volume (r=0.72, p<0.001), end-diastolic volume (r=0.63, p=0.001), and inversely with LVEF (r=−0.74, p<0.001). Baseline HBW similarly predicted LVEF at 6 months in comparison to baseline infarct size (r=0.62, p=0.001 and r=0.58, p=0.002). HBW and PSD improved over the follow up period (−24.1±35.9 degrees, p=0.003 and −8.7±14.6 degrees, p=0.006, respectively), and improvement in HBW correlated with reduction in LV end-systolic volumes (r=0.43, p=0.034).
Conclusions: After STEMI, subjects exhibit mechanical dyssynchrony as measured by GSPECT phase analysis without evidence of electrical dyssynchrony. Improvement in mechanical dyssynchrony correlates with beneficial ventricular remodeling. The full predictive value of this measure in post-infarct patients warrants further study.