Mechanical dispersion as a predictor of arrhythmic death in patients with ischaemic and non-ischaemic left ventricular dysfunction

Background: Arrhythmic death is a leading cause of mortality among patients with ischaemic and non-ischaemic heart failure. Solid evidence shows that, among high-risk patients with left ventricular dysfunction, implantable cardioverter-defibrillators (ICD) is a cost-effective treatment in the primary and secondary prevention of life threatening ventricular arrhythmia. The decision to implant an ICD should take into account several factors including clinical history, NYHA class, left ventricular ejection fraction and life expectancy. Myocardial strain assessed using speckle tracking echocardiography represents a novel tool to quantify global and regional myocardial function. It has been recently shown that mechanical dispersion is a predictor of ventricular arrhythmias in patients after myocardial infarction. Purpose: The aim of our study was to evaluate the correlation between myocardial strain and ventricular arrhythmias in patients treated with ICD in primary or secondary prevention. Methods: We recruited 48 patients with ischaemic and non-ischaemic dilative cardiomyopathy (39 male, 9 female), middle aged (63.7 years), implanted with ICD or CRT-D in primary (34 pts) or secondary (14 pts) prevention. Each patient underwent clinical examination, ECG, transthoracic echocardiography with the analysis of traditional and speckle tracking parameters (Global Longitudinal Strain GLS, Mechanical Dispersion MD) and periodical device interrogation before and after device implantation. The average follow-up was 34.6 months. Results: During the follow-up, life-threatening ventricular arrhythmias occurred in 16 patients (events group). No statistical difference in terms of age, gender, cardiovascular risk factors and etiology of the myocardial disfunction were observed. Furthermore, echocardiographic traditional parameters (LVEF) and wall motion score index were comparable between the two groups before and after device implantation. In univariate analysis there were no difference in terms of GLS (p=0,58), but there was a significant correlation with MD (SD time to peak 112.7±33 msec vs 68.5±30.8 msec, p=0.0001), supported also by ROC curve analysis (r=-0,56, p=0.0001). The correlation between arrhythmic events and MD was confirmed in both ischaemic and non-ischaemic patients (r=0.61, p=0.001 e r=0.48, p=0.0178). A MD value ≥103 msec has been found to be a good predictor of ventricular sustained arrhythmias in the two groups (ischaemic pts: log rank p=0.012, Ki square 6.0 - non ischaemic pts: log rank p=0.015, Ki square 5.885). Conclusions: Mechanical dispersion evaluated using speckle tracking technique is a valid technique for risk stratification of ventricular arrhythmias in patients with dilative ischaemic or non-ischaemic cardiomyopathy.