Superior vena cava flow and tricuspid anular motion after cardioversion of atrial fibrillation, and role of right atrial relaxation on systolic venous return.

To determine whether atrial relaxation or systolic descent of the tricuspid anulus is the predominant factor determining systolic venous return, 22 patients with atrial fibrillation were studied. Venous return (i.e., superior vena cava (SVC) flow) was measured using pulsed Doppler echocardiography. Systolic descent of the tricuspid anulus (i.e., total excursion of tricuspid anulus during systole) was also measured using echocardiography. Serial examinations were performed before and after cardioversion of atrial fibrillation in 15 patients. In 11 patients, both the total excursion of the tricuspid anulus and SVC flow were examined in relation to the ratio of the preceding to the pre-preceding RR interval (R2/R1). Systolic forward flow of SVC increased as the ratio of late diastolic to total excursion of the tricuspid anulus (i.e., right atrial systolic function) increased. It correlated significantly with the ratio of late diastolic to total excursion of the tricuspid anulus but not with total excursion. Total excursion of the tricuspid anulus correlated significantly with R2/R1, but systolic forward flow of SVC did not. These results indicate that atrial relaxation rather than systolic descent of the tricuspid anulus was the predominant factor determining systolic forward flow in the SVC.