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 differen t pacing rates and the feasibility of identifying patients prone to pa cemaker syndrome by means of a Doppler and two-dimensional echocardiog raphic technique. Twenty-two sick sinus patients who received ventricu lar-demand permanent pace makers constituted the study group. The prox imal inferior vena cava (IVC) diameters were measured by two-dimension al echocardiography. Fourteen patients had VA conduction by preimplant electrophysiologic study or paced electrocardiogram (Group II), while the other 8 patients presented no VA conduction (Group I). Abnormal s ystolic retrograde flow in the hepatic vein following each paced beat could be demonstrated in those patients with VA conduction in the basa l state. In the 8 patients without VA conduction, the IVC diameters we re significantly increased during rapid right ventricular pacing in th ose with left ventricular dysfunction (n=4) as compared with those wit h 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 p aced 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 al 120 bpm paced r ate, 7% +/- 6% vs -4% +/- 5%, P < 0.005). Four of 7 patients in group IIA developed symptoms of pacemaker syndrome. However, there were no s ignificant changes in the severity of tricuspid regurgitation at diffe rent pacing rates. These data suggest that detection of abnormal systo lic retrograde flow in the hepatic vein and measurement of percent cha nges in IVC diameters during high pacing rates could be helpful in ide ntifying Possible pacemaker syndrome in patients receiving ventricular ;demand pacemakers.