The implementation of speckle tracking echocardiography for cardiac resynchronization therapy optimization. A rotational myocardial mechanics interpretation

Abstract

Background: Cardiac resynchronization therapy (CRT) has an additive therapeutic influence on left ventricular function in heart failure patients, but the underlying mechanisms through which it works are not completely explained. Our aim was to further elucidate the role of this intervention via rotational mechanics using 2D speckle tracking echocardiography (2D-STE). Results: We investigated 46 patients (65 ± 9 years) who received CRT. All enrolled patients were assessed on admission by 2D-STE and 6 minute walk test (6 min WT) and followed in the outpatient device clinic by 2D-STE (at one week and 6-month post-implantation) and 6 min WT (at 6 months post-implantation). On their first appointment all biventricular systems were optimized by atrioventricular delay optimization and by changing the temporal activation of ventricular electrodes aiming to reach the highest left ventricular effective stroke volume across all activation options. A new 2D-STE based index (twist integral) targeting to assess the rotational mechanics of the whole cardiac cycle was also measured to further explain the CRT response. Twenty-two (48%) patients with dilated cardiomyopathy as the predominant aetiology of heart failure were responders at 6-month follow-up. The commonest selected mode that was related with the greatest left ventricular performance response was the simultaneous activation of the 2 ventricular leads (39%). The strongest predictor of CRT response was the improvement of effective stroke volume between admission and first appointment at clinic, followed by the improvement of twist integral, the non-existence of coronary artery disease, and the improvement of peak systolic twist. Conclusions: Additional CRT optimization via changing the temporal activation of ventricular electrodes is beneficial for left ventricular performance in heart failure patients. Rotational mechanics essentially explain the beneficial CRT contribution to these patients.