Prognostication in 3-Vessel Coronary Artery Disease Based on Left Ventricular Ejection Fraction During Exercise

Abstract

Background —Previous data indicate that left ventricular ejection fraction (LVEF) provides prognostic information among patients with coronary artery disease (CAD), but the value of such testing specifically for defining benefits of coronary artery bypass grafting (CABG) may relate to severity of exercise-inducible ischemia measured noninvasively before surgery. Methods and Results —To determine the independent prognostic importance of preoperative ischemia severity for predicting outcomes of CABG among patients with extensive CAD, we monitored 167 stable patients with angiographically documented 3-vessel CAD (average follow-up of 9 years in event-free patients) who previously had undergone rest and exercise radionuclide cineangiography. Their course was correlated with data obtained during initial radionuclide testing, coronary arteriography, and clinical evaluation at study entry. Fifty-two patients received medical treatment only, and 115 underwent CABG (44 early [≤1 month after initial study]). Multivariate Cox model analysis indicated that change (Δ) in LVEF from rest to exercise during radionuclide study was the strongest independent predictor of major cardiac events ( P =0.003) before surgery and also predicted magnitude of CABG benefit ( P =0.04). Patients with ΔLVEF −8% or less derived significant survival-prolonging and event-reducing benefit from CABG performed ≤1 month after initial testing ( P <0.02 for cardiac death and P =0.008 for cardiac events], early CABG versus medical-treatment-only patients); similar benefits were absent among patients with ΔLVEF more than −8%, and among those in whom CABG was deferred. Conclusions —Assessment of ischemia severity based on LVEF response to exercise enables effective prognostication among patients with 3-vessel CAD and defines the likelihood of life-prolonging and event-reducing benefits from CABG.

Time-dependent bias was common in survival analyses published in leading clinical journals

“…In three studies (7.9% [2.7-20.8%]), correction of time-dependent bias could have made the permissive hazard ratio or relative risk statistically significant [47,48,86]. In 20 studies where the relative risk was less than 1 (52.6% [37.3-67.5%]), correction of timedependent bias could have nullified previously significant hazard ratios or relative risks or could have transformed the preventive relative risk into a permissive hazard ratio or relative risk [45,50,52,53,55,57,[61][62][63]65,71,77,78,81,83,[87][88][89][90][91].…”

Ventricular asynchrony: A shift to the right?

“…4,5 Further work demonstrated that synchronicity of LV contraction could be derived from RNV by Fourier analysis of pixel by pixel labeled RBC time-activity curves, assigning a phase to each pixel (percent of the R-R interval from 0°-360°) to identify time of maximum contraction.…”

“…2,3 Clinical trials soon showed that noninvasively determined LVEF was a strong predictor of survival in a broad range of heart diseases. 4,5 Further work demonstrated that synchronicity of LV contraction could be derived from RNV by Fourier analysis of pixel by pixel labeled RBC time-activity curves, assigning a phase to each pixel (percent of the R-R interval from 0°-360°) to identify time of maximum contraction. 6 Synchronicity has important effects on LV performance: patients with inter-or intra-ventricular asynchrony have lower LVEF relative to normal control subjects.…”