Post infarction risk stratification using the 3-D angle between QRS complex and T-wave vectors

Abstract

Present experience with prospective identification of patients who might benefit from prophylactic antiarrhythmic intervention is restricted to risk stratification using left ventricular ejection fraction (LVEF). The precision of LVEF-based identification of high risk patients is neither highly sensitive nor highly specific. This study investigated risk stratification of 466 survivors of acute myocardial infarction (86 women, mean age 57.5 years) for whom a 5-year follow-up was available. During the follow-up 67 patients died and 24 of these events were sudden arrhythmic deaths. In addition to LVEF, patients were stratified by mean heart rate, heart rate variability and the slope of heart rate turbulence, all derived from 24-hour Holter recording obtained before hospital discharge, and by the 3D angle between QRS complex and T wave vectors (total cosine R-to-T, TCRT) obtained from digital resting electrocardiogram before hospital discharge. Individual risk characteristics and their combinations were evaluated by calculating the areas under the receiver operator characteristics (ROC). The bootstrap technology was used to investigate these statistically. For the stratification of both all cause mortality and sudden arrhythmic death, TCRT was the strongest risk stratifier (area under ROC of 0.6857 ± 0.0367, and 0.7275 ± 0.0544, respectively) that compared very favourably to LVEF (area under the ROC of 0.6610 ± 0.0362 and 0.6346 ± 0.0595, for all cause and arrhythmic death prediction, both P < 10 −10 for the comparison with TCRT). TCRT was also stronger in combination with other stratifiers, eg, TCRT + LVEF (area under ROC of 0.7631 ± 0.0325 and 0.8057 ± 0.0473, for all cause and arrhythmic death prediction) was stronger than mean heart rate + LVEF (area under ROC of 0.7396 ± 0.0298 and 0.7673 ± 0.0445, respectively, both P < 10 −10 for comparison with TCRT + LVEF). Hence the 3D QRS-T angle is a very powerful risk stratifier especially suited for the prediction of sudden arrhythmic death. It should be prospectively investigated in future trials of prophylactic antiarrhythmic interventions.