Recurrency of ventricular arrhythmias after myocardial infarction: correlation with left ventricular function assessed by STI

Background. A myocardial strain reduction by speckle tracking imaging (STI) can potentially be a direct indicator of non-viable myocardium and sudden cardiac death (SCD) risk and could help in identifying high-risk patients currently missed by left ventricular ejection fraction (LVEF) criteria. We aimed to compare strain data of patients with structural heart disease with and without ventricular tachycardia (VT) regardless of LVEF. Methods. We studied 84 patients (pts) with previous myocardial infarction (age, 60±14 years) scheduled for cardioverter-defibrillator (ICD) implantation. Forty-two pts had documented VT and 42 pts presented with no VT. Exclusion criteria were previous coronary artery surgery, moderate-severe or severe valve regurgitation, atrial fibrillation, and left bundle branch block. Left ventricular (LV) function and volumes and score index were determined by two-dimensional echocardiography. Longitudinal LV strain was defined as the average of negative longitudinal strains of 6 segments of the septal and lateral walls in the apical 4-chamber view. Average radial and circumferential strain of 6 mid-LV segments was determined in the mid-short-axis view. Global strain was obtained by averaging the maximum systolic shortening in a 16-segment model. The analysis of strain parameters was performed offline using customized computer software (EchoPAC, version 9.0, GE Ultrasound). Results. No statistical difference in LVEF and LV volumes was shown in pts with recurrent ventricular arrhythmias and those without VT. There were no differences in QRS and QTc duration or in standard global and regional LV function echocardiographic parameters between pts with or without VT occurring during follow-up. Multivariate analysis revealed that global (p=0.021) and posterior wall circumferential strain (p=0.006) were strong and independent predictors of the occurrence of arrhythmic events. The area under the curve (AUC) for QTc was 0.33 yielding a sensitivity and specificity of, respectively, 51% and 63% to predict arrhythmias and AUC for EF was 0.49 yielding a sensitivity and specificity of, respectively, 54% and 68%. AUC for posterior wall circumferential strain was 0.78 and the optimal cutoff value -6.4% for a sensitivity of 69% and a specificity of 88% in predicting arrhythmic events. Conclusions. In patients with previous myocardial infarction scheduled for ICD therapy circumferential strain was the strongest predictor of spontaneous ventricular arrhythmias among other clinical and echocardiographic variables such as score index and LV function and volumes.