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

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 min walk test (6 min WT) and followed in the outpatient device clinic by 2D-STE (at 1 week and 6 months post-implantation) and 6 min WT (at 6 months post-implantation). On their first appointment all biventricular systems were optimised by atrioventricular delay optimisation 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 were responders at 6-month follow-up and most of them had dilated cardiomyopathy. 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 absence of coronary artery disease, and the improvement of peak systolic twist. CONCLUSIONS: Additional CRT optimisation via changing the temporal activation of ventricular electrodes is beneficial for left ventricular performance in heart failure patients. The success of biventricular pacing may also be explained by the improvement of left ventricular rotational mechanics.