Transesophageal echocardiographic color Doppler evaluation of pulmonary vein flow during ventricular pacing.

Hemodynamic changes induced by ventriculo-atrial retroconduction has been considered an important factor in pacemaker syndrome. The contraction of atrial muscles, when the mitral valve is closed, induces a reverse systolic flow into the pulmonary veins, because the outlet of the pulmonary vein in the left atrium is not protected by a valve. The profile of the pulmonary vein forward flow of 25 patients was examined using transesophageal echocardiography (TEE) technique. Doppler evaluation of velocity-time integrals of forward flow (fVTI) and reverse flow (rVTI) was measured both during sinus rhythm or fully automatic (DDD) pacing, and ventricular demand pacing (VVI) accompanied by ventriculoatrial (VA) retroconduction or atrioventricular (AV) dissociation. The mean fVTI was reduced from 21.1 cm +/- 6.2 cm in DDD or sinus rhythm (SR) to 16.4 cm +/- 6.6 cm in VVI (p < 0.001). The mean rVTI was increased from 1.4 cm +/- 0.8 cm in DDD or SR to 4.3 cm +/- 1.8 cm in VVI (p < 0.001). The degree of such alterations varied considerably from patient to patient and this may explain the variability of clinical symptoms reported for pacemaker syndrome. It has not been possible to establish a direct correlation between the magnitude of hemodynamic changes and the severity of the symptoms observed because all the patients were in sequential stimulation or in SR and were temporarily submitted to VVI stimulation during the echocardiographic examination.