Cardiac resynchronization therapy by multipoint pacing improves response of left ventricular mechanics and fluid dynamics: A three-dimensional and particle image velocimetry echo study

Conventional biventricular pacing (BiV) involves pacing from the right ventricle (RV), and the left ventricle (LV) usually using a single bipolar lead at one site via the coronary sinus (CS), with the aimto restore electrical and mechanical synchrony in heart failure (HF) patients.1 However, one-third of patients fail to clinically respond to cardiac resyncronization therapy (CRT), which may be partially due to a suboptimal location of the LV lead position with persistent LV dyssynchrony.2 In search for improvements in CRT, several authors have proposed a multisite LV stimulation using multiple leads in different branches of the CS.3 However, this technique is associated with increased procedure duration, fluoroscopy exposure, and potential complications. A new approach that involves a multisite pacing performed within a single CS branch by using a single quadripolar lead (multipoint pacing, or MPP; St. Jude Medical, Sylmar, CA) has been suggested recently. Benefits in acute haemodynamics using pressure-volume loop analysis and LV dyssynchrony using two dimensional echocardiographic (2DE) have been demonstrated with MPP in comparison with BiV.4-7 Nevertheless, the effects of MPP on LV dyssynchrony using three-dimensional echocardiography (3DE) and on diastolic filling have not been established yet. Echocardiographic particle imaging velocimetry (Echo-PIV) is an emerging imaging technique, which allows intraventricular fluid dynamics blood assessment and characterization of diastolic vortex formation that may play a key role in LV filling efficiency.8-12 Recent fluid dynamics data demonstrated that in normal LV, the blood flow is characterized by a longitudinal alignment along the base-apex direction of the intraventricular hemodynamic fluid dynamics in compliance with the empting-filling process.12 Conversely, HF patients show an irregular vortex formation with local stagnation resulting in transversal forces and loss of the physiological longitudinal orientation of the intraventricular velocites.8-12 Changes in intraventricular flow dynamics by CRT are supposed to result in a longitudinal alignment restoration of LV intraventricular velocities.12 Accordingly, the aim of the present studywas to characterize the effect of MPP compared to BiV on: (i) LV geometry and function assessed by conventional 2DE and 3DE and (ii) LV flow dynamics assessed by Echo- PIV.