Influence of gravity on pulmonary venous flow velocity patterns: Analysis of left and right pulmonary venous flow velocities in left and right decubitus positions

Background The pulmonary venous flow signal measured by transesophageal ech ocardiography is generally recorded from the left upper pulmonary vein in t he left lateral decubitus position, whereas that by transthoracic echocardi ography is from the right upper pulmonary vein in the left semi-lateral dec ubitus position. The purpose of this study was to evaluate the influence of the postural change on the peak flow velocities of the left and right pulm onary veins and whether the parameters of the left and right pulmonary veno us flow can be used interchangeably Methods and Results The study group consisted of 37 patients with normal le ft ventricular filling pressure and in whom the systolic forward flow signa ls From both pulmonary veins recorded in the left and right lateral decubit us positions were clear enough to differentiate as biphasic. The peak early systolic (peak S1) and diastolic velocities were significantly increased w hen the pulmonary vein was on the recumbent subject's upper side, whereas t he peak late systolic velocity (peak S2) was significantly increased when t he pulmonary vein was on the recumbent subject's lower side. The peak S1 wa s higher than the peak S2 when the pulmonary vein was on the recumbent subj ect's upper side, whereas the reverse relation was seen when the pulmonary vein was on the recumbent subject's lower side. Conclusions We should take into consideration the body position and the sid e on which the pulmonary vein is situated in evaluating the peak flow veloc ities of the pulmonary veins.