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Effects of Right Ventricular Pacing on Ventriculoatrial Conduction and Systemic Venous Responses in Sick Sinus Patients

This study was designed to assess the ventriculoatrial (VA) conduction and systemic venous responses to right ventricular pacing at different pacing rates and the feasibility of identifying patients prone to pacemaker syndrome by means of a Doppler and two- dimensional echocardiographic technique. Twenty-two sick sinus patients who received ventricular-demand permanent pace makers constituted the study group. The proximal inferior vena cava (IVC) diameters were measured by two-dimensional echocardiography. Fourteen patients had VA conduc tion by preimplant electrophysiologic study or paced electrocardiogram (Group II), while the other 8 patients presented no VA conduction (Group I). Abnormal systolic retrograde flow in the hepatic vein following each paced beat could be demonstrated in those patients with VA conduction in the basal state. In the 8 patients without VA conduction, the IVC diameters were significantly increased during rapid right ventricular pacing in those with left ventricular dysfunction (n=4) as compared with those with normal left ventricular function (n=4) (% increment at 120 beats per minute [bpm] pacing rate, 9% ±6% vs 2% ±3%, P = 0.03). Seven of 14 patients with retrograde conduction showed a 1:1 or 2:1 ratio of paced beat to retrograde flow, at 120 bpm pace rate (Group IIA). Their IVC diameter significantly increased at higher pacing rates than those presenting a higher ratio (group IIB) (% increment at 120 bpm paced rate, 7% ±6% vs -4% ±5%, P < 0.005). Four of 7 patients in group IIA developed symptoms of pacemaker syndrome. However, there were no significant changes in the severity of tricuspid regurgitation at different pacing rates. These data suggest that detection of abnormal systolic retrograde flow in the hepatic vein and measurement of percent changes in IVC diameters during high pacing rates could be helpful in identifying possible pacemaker syndrome in patients receiving ventric ular-demand pacemakers.