Predicting ventricular arrhythmias in patients with ischemic heart disease: clinical application of the ECG-derived QRS-T angle.

BACKGROUND: In patients with primary prevention implantable cardioverter-defibrillators (ICDs), the incidence of life-threatening ventricular arrhythmias resulting in ICD therapy is relatively low, prompting for better risk stratification. The aim of this study was to assess the value of the QRS-T angle for prediction of ICD therapy and mortality in primary prevention patients with ischemic heart disease. METHODS AND
RESULTS: ICD patients (n=412, 361 men; age, 63+/-11 years) with ischemic heart disease and a left ventricular ejection fraction < or = 40% were included. After device implantation, the occurrence of appropriate ICD therapy and mortality was noted. A survival analysis was performed comparing patients with a planar QRS-T angle < or = 90 degrees (n=124, 30%) with patients with a planar QRS-T angle >90 degrees before device implantation. Furthermore, patients with a spatial QRS-T angle < or = 100 degrees (n=56, 14%) were compared with patients with a spatial QRS-T angle >100 degrees , before implantation. For patients with a planar QRS-T angle >90 degrees as compared with < or = 90 degrees , the adjusted hazard ratio for the occurrence of appropriate device therapy was 2.4 (95% CI, 1.1 to 5.2); a spatial QRS-T angle >100 degrees was associated with an adjusted hazard ratio of 7.3 (95% CI, 1.0 to 53.8). Furthermore, a spatial QRS-T angle < or = 100 degrees exhibited a positive predictive value of 98% (95% CI, 95 to 100) for the prediction of an appropriate therapy-free follow-up.
CONCLUSIONS: A wide QRS-T angle is a strong predictor of appropriate device therapy in primary prevention ICD recipients with ischemic heart disease. Furthermore, a spatial QRS-T angle < or = 100 degrees might be of value in the identification of patients in whom, although currently indicated, ICD treatment should be reconsidered.