Quantitative Measures of Electrocardiographic Left Ventricular Mass, Conduction, and Repolarization, and Long-Term Survival After Coronary Artery Bypass Grafting

Abstract

Background— Quantitative ECG measures of left ventricular mass and repolarization predict outcome in population-based cohorts and patients with hypertension. We assessed the prognostic value of preoperative quantitative electrocardiography in patients who underwent isolated coronary artery bypass grafting. Methods and Results— For 6 years we followed 8166 patients who underwent primary isolated coronary artery bypass grafting between 1990 and 2003, all of whom had routine preoperative ECGs. With use of specialized digital software, quantitative measures were recorded on ventricular rate, P duration, PR interval, QRS duration, QT interval, QRS axis, Sokolow-Lyon and Cornell voltages, and ST-segment depression and slope. There were 1516 deaths. After adjustment for age, gender, clinical characteristics, left ventricular ejection fraction, and other confounders, death was independently predicted by ventricular rate (adjusted hazard ratio [AHR] for 90 versus 60 beats per minute, 1.34; 95% confidence interval [CI], 1.21 to 1.50; P <.0001), PR interval (AHR for 200 versus 150 ms, 1.05; 95% CI, 1.00 to 1.10; P <.0001), QRS duration (AHR for 120 versus 80 ms, 1.24; 95% CI, 1.07 to 1.44; P <.0001), Sokolow-Lyon voltage (AHR for 3.5 versus 1.5 mV, 1.18; 95% CI, 1.05 to 1.31; P <.0001), and ST-segment slope (AHR for −0.1 versus 0 mV, 1.16; 95% CI, 1.02 to 1.31; P <.0001). We derived a quantitative ECG score and demonstrated that, with the exception of age, it was the most powerful predictor of long-term death. Conclusions— Quantitative ECG measures of left ventricular rate, mass, and repolarization are predictive of mortality among patients who underwent isolated coronary artery bypass grafting. These findings suggest that quantitative electrocardiography may be valuable for risk stratification in patients with severe coronary artery disease.