Acute Mechanical Effect of Right Ventricular Pacing at Different Sites Using Velocity Vector Imaging

OBJECTIVE: Velocity vector imaging (VVI) allows noninvasive measurement of left ventricular (LV) strain and rotation angle-independently. We investigated strain, rotation and myocardial synchrony when pacing at different sites in the right ventricle to determine which site yields the most physiological pacing, as determined with VVI imaging. METHOD: Thirty-one patients with normal LV function referred for elective electrophysiology exam were used in this study. Catheters (6F quadripolar) were positioned in the right atrium, right ventricular apex, right ventricular outflow tract, and His bundle after electrophysiology exam was done. Regional and global LV circumferential strain (CS), radial strain (RS), and LV rotation of LV short-axis measurements were obtained. Two dyssynchrony parameters (AS-P delay and SDt(6S)) of CS and RS were obtained. Compare these values among each pacing, respectively. RESULT: CS, RS, and twist, which represent the LV systolic function, were significantly reduced in RVOT pacing and RVA pacing than RA pacing. Two dyssynchrony parameters (AS-P delay and SDt(6S)) were significantly longer in response to RVOT or RVA pacing compared to RA pacing. No significant differences were found between RVOT pacing and RVA pacing. CS and RS were obviously reduced in the regions surrounding the pacing site. There was no significant difference in CS, RS, twist, and mechanical dyssynchrony parameters when comparing His and RA pacing. CONCLUSION: Among these alternate right ventricular pacing locations, His bundle pacing is most like physiological pacing. Both RVOT pacing and RVA pacing worsen the normal LV systolic function with regard to strain, twist, and mechanical dyssynchrony along the LV short axis.