Right Ventricular Outflow Tract Pacing Causes Intraventricular Dyssynchrony in Patients With Sick Sinus Syndrome: A Real-Time Three-Dimensional Echocardiographic Study

Background

The optimal right ventricular pacing site remains controversial. The aim of this study was to assess how acute right ventricular outflow tract (RVOT) pacing affects global left ventricular function and intraventricular dyssynchrony of the left ventricle.

Methods

Thirty-six patients with sick sinus syndrome and intact intrinsic atrioventricular conduction were enrolled. All patients underwent dual-chamber permanent pacemaker implantation, with the atrial lead placed in the right atrial appendage and the right ventricle lead positioned at the septal site of the RVOT. Chamber size, dyssynchrony index, myocardial performance index, and global left ventricular ejection fraction were determined using transthoracic two-dimensional echocardiography, tissue Doppler echocardiography, and real-time three-dimensional echocardiography.

Results

RVOT pacing increased the myocardial performance index (0.42 ± 0.21 with RVOT pacing vs 0.35 ± 0.21 without RVOT pacing, P = .002) and decreased the global left ventricular ejection fraction on real-time 3-dimensional echocardiography (51.4 ± 6.2% with RVOT pacing vs 55.9 ± 7.1% without RVOT pacing, P = .001). Intraventricular dyssynchrony of the left ventricle induced by RVOT pacing was determined by increased septal-to-posterior wall motion delay (69.7 ± 54.0 ms with RVOT pacing vs 22.8 ± 22.3 ms without RVOT pacing, P < .0001), increased systolic and diastolic dyssynchrony by tissue Doppler echocardiography, and increased systolic dyssynchrony index when assessed using real-time three-dimensional echocardiography (5.56 ± 1.74% with RVOT pacing vs 4.05 ± 1.61% without RVOT pacing, P < .0001).

Conclusion

Acute RVOT pacing adversely affects left ventricular function and increases intraventricular dyssynchrony in patients with sick sinus syndrome.

Keywords: Cardiac pacing, Echocardiography, Intraventricular dyssynchrony, Sick sinus syndrome, Ventricular function

Abbreviations: 2D, Two-dimensional, 3D, Three-dimensional, MOST, Mode Selection Trial, RT3DE, Real-time 3D echocardiography, RV, Right ventricular, RVOT, RV outflow tract, SSS, Sick sinus syndrome, Te, Times to peak myocardial early diastolic velocity, Te-SD, Standard deviation of Te, Ts, Times to peak myocardial sustained systolic velocity, Ts-SD, Standard deviation of Ts