Abstract 15075: QRS-T Morphology Measured from Exercise Electrocardiogram as a Predictor of Cardiac Mortality
Purpose: Total cosine R-to-T (TCRT) measured from standard 12-lead ECG reflects the spatial relationship between depolarization and repolarization wavefronts. Reduced TCRT value indicates an increased risk of mortality. We tested the hypothesis that measurement of TCRT or QRS/T angle from exercise ECG gives even more powerful prognostic information.
Methods: The prognostic significance of the rate-dependence of TCRT and QRS/T angle were assessed from standard exercise ECG recordings in 1297 patients (age 56±13 years [mean±SD], 67% males) undergoing a clinically indicated bicycle stress-test.
Results: During an average follow-up of 45±12 months, 74 patients died (5.7%); 34 (2.6%) were cardiac deaths and 24 (1.9%) were sudden cardiac deaths. TCRT and QRS/T angle had a correlation with the RR intervals in the total cohort, but the individual responses were variable, e.g. median correlation coefficient between TCRT and RR intervals (TCRT-RR) was 0.89 with an inter-quartile range of 0.55 − 0.98. After adjustments with age, beta-blockers, body mass index, coronary heart disease, diabetes, left ventricular ejection fraction, maximum heart rate, metabolic equivalent, previous infarction, sex and smoking, reduced TCRT-RR value during the recovery phase of exercise ECG was a stronger predictor of cardiac death (adjusted HR 3.6; 95%CI: 1.8–7.2; p=0.001) than TCRT measured from baseline 12-lead ECG (adjusted HR 1.8; 95% CI: 1.2–2.9; p=0.01). Poor TCRT-RR correlation coefficient both during the exercise and recovery was specifically related to a high risk of sudden cardiac death (adjusted HR 7.1; 95%CI; 2.5–20.3; p<0.001; Figure 1).
Conclusions: Loss of rate-dependence of depolarization and repolarization wavefronts is a strong predictor of cardiac death, especially of sudden cardiac death.
- © 2010 by American Heart Association, Inc.