Objective—To study the mechanisms underlying the dominant `a' wave seen in patients with primary pulmonary hypertension.
Design—Retrospective and prospective examination of the jugular venous pulse recording, flow in the superior vena cava, and Doppler echocardiographic studies.
Setting—A tertiary referral centre for both cardiac and pulmonary disease, with facilities for invasive and noninvasive investigation, and assessment for heart and heart-lung transplantation.
Patients—12 patients with primary pulmonary hypertension, most being considered for heart-lung transplantation.
Results—Two distinct patterns of venous pulse and superior vena caval flow were identified: a dominant `a' wave with no `v' wave, an absent or poorly developed `y' descent, and exclusively systolic downward flow in the superior vena cava (group 1, n = 8), and a dominant `v' wave, deep `y' descent and exclusively diastolic downward flow in the superior vena cava (group 2, n = 4). A comparison between the two groups showed age (mean (SD)) 42 (18) ν 36 (7) years, RR interval 700 (65) ν 740 (240) ms, left ventricular end diastolic dimension 3·6 (0·8) ν 3·2 (1·0) cm and end systolic dimension 2·1 (0·5) ν 2·3 (0·3) cm, right ventricular end diastolic dimension 2·6 (0·5) ν 2·8 (0·6) cm, and pressure drop between right ventricle and right atrium 60 (8) ν 70 (34) mm Hg to be similar. Duration of tricuspid regurgitation 520 (30) ν 420 (130) ms and the time interval of pulmonary closure to the end of the tricuspid regurgitant signal 140 (30) ν 110 (40) ms were longer in group 1 compared with group 2, whereas right ventricular filling time was much shorter 180 (70) ν 350 (130) ms. In seven patients from group 1, a single peak of forward tricuspid flow was present, but this pattern was seen in only one patient from group 2.
Conclusions—In patients with primary pulmonary hypertension, the apparent `a' wave seen in the venous pulse is, in fact, a summation wave. It is probably the result of large pressure changes that must underlie rapid acceleration and deceleration of blood across the tricuspid valve when the right ventricular filling time is short.