Postexercise recovery of the spatial QRS/T angle as a predictor of sudden cardiac death

Postexercise measurement of heart rate (HR) recovery and QT interval dynamics provides prognostic information in various patient populations.

The purpose of this study was to assess whether the measurement of the spatial relationship between the depolarization and repolarization wavefronts (total cosine R-to-T [TCRT]) during the postexercise recovery phase would yield prognostic information.

The population consisted of 1297 patients (56 ± 13 years; 67% men) who performed a clinically indicated bicycle stress test. The exercise-recovery hysteresis of TCRT was quantified from the 12-lead exercise electrocardiogram by measuring the TCRT/HR loop area bounded by the exercise and first 3-minute postexercise recovery curves. The HR-corrected TCRT/HR hysteresis was calculated by dividing the area with the HR decrement during the first 3 minutes of recovery. HR recovery was measured at 1 minute postexercise recovery. End points were cardiac death and sudden cardiac death.

During an average follow-up of 45 ± 12 months, 74 patients died (5.7%); 35 (2.6%) were cardiac deaths and 24 (1.9%) were sudden cardiac deaths. Reduced TCRT/HR loop area and TCRT/HR hysteresis were associated with cardiac mortality (P <.001). After adjustments for clinical variables, including ejection fraction, TCRT/HR loop area remained an independent predictor of cardiac death (hazard ratio 5.6; 95% confidence interval 1.6-19.1; P = .007) and sudden cardiac death (10.7; 95% confidence interval 1.4-83.7; P = .024). HR recovery did not remain a significant predictor in the multivariate analysis.

Attenuated hysteresis of the depolarization and repolarization wavefronts during postexercise recovery is associated with an increased risk of cardiac and sudden cardiac death. Analysis of repolarization dynamics from exercise electrocardiogram represents a promising tool for risk stratification.