Terminal QRS axis as a promising method to predict ventricular arrhythmogenicity in patients with prior myocardial infarction

Abstract

Objectives: Myocardial infarctions (MI) are commonly associated with ventricular arrhythmias, such as ventricular ectopic beats (VES) or ventricular tachycardia (VT). However, current criteria to determine which MI patient would benefit from an implantable cardioverter-defibrillator (ICD) remain inadequate. This study assesses whether the terminal axis (TA) of the QRS complex on a 12-lead electrocardiogram may serve as a new method to differentiate between arrhythmogenic and non-arrhythmogenic MIs, thereby identifying the best candidates for ICD implantation. Methods: TA was defined as the frontal plane axis of the terminal QRS activation at 20 ms before the end of the QRS. TAs were retrospectively calculated in 21 inferior MI patients with associated VES or VT (mean age 61.3 ± 14.7 years, 78.3% male) and in 82 inferior MI patients without reported arrhythmias (mean age 68.0 ± 6.6 years, 94.4% male). Results: Arrhythmogenic inferior MI patients were more often treated with coronary artery bypass grafting (22.2% vs 0%, p ¼ 0.0021) and less often with percutaneous coronary intervention (72.2% vs 98.3%, p ¼ 0.0021), presented with a higher incidence of left bundle branch block (22.2% vs 0%, p ¼ 0.0021) and had a significantly lower ejection fraction (41.4% vs 54.3%, p < 0.0001). TA direction of arrhythmogenic inferior MI patients differed significantly from TA direction of nonarrhythmogenic inferior MI patients (104.05 (CI¼ [82.06; 126.05]) vs 221.31 (CI ¼ [182.97; 259.65]), p ¼ 0.0001). Furthermore, an arrhythmogenic range for TA direction on a circular diagram was identified (26.04 to 153.95 ), with a sensitivity of 80.95% and a specificity of 73.17% to identify arrhythmogenicity. Conclusions: In contrast to non-arrhythmogenic inferior MI patients, TA in arrhythmogenic inferior MI patients shows a predilection towards the inferior cardiac region, which corresponds to delayed activation and a substrate for arrhythmia. TA could therefore be useful to differentiate between arrhythmogenic and non-arrhythmogenic MIs, representing a valuable additional criterium when selecting patients for ICD implantation.