Acute Effects of Right Ventricular Apical Pacing on Left Ventricular Synchrony and Mechanics

BACKGROUND: Chronic right ventricular (RV) apical pacing has a detrimental effect on left ventricular (LV) function. However, the acute effects of RV apical pacing on LV mechanics remain unclear. The purpose of the study was to assess the acute impact of RV apical pacing on global LV function, evaluating LV contraction synchrony and LV shortening and twist, using 2D speckle-tracking strain imaging. METHODS AND RESULTS: A group of 25 patients with structural normal hearts referred for electrophysiological study were studied. Two-dimensional echocardiography was performed at baseline and during RV apical pacing at the time of the electrophysiological study. Changes in LV synchrony and mechanics (longitudinal shortening and twist) were assessed using speckle-tracking strain imaging. In addition, 25 controls matched by age, sex, and LV function were studied during sinus rhythm. The group of patients (44+/-12 years, 10 men) and the group of controls (48+/-3 years, 8 men) showed comparable LV synchrony, LV longitudinal shortening, and LV twist at baseline. However, during RV apical pacing, a more dyssynchronous LV contraction was observed in the patients (from 21 ms Q(1):10, Q(3):53 to 91 ms Q(1):40, Q(3):204, P<0.001) together with an impairment in LV longitudinal shortening (from -18.3+/-3.5% to -11.8+/-3.6%, P<0.001) and in LV twist (from 12.4+/-3.7 degrees to 9.7+/-2.6 degrees , P=0.001). CONCLUSIONS: During RV apical pacing, an acute induction of LV dyssynchrony is observed. In addition, LV longitudinal shortening and LV twist are acutely impaired.