Immediate and short-term effects of pulmonary artery banding on left ventricular performance in foetal sheep

To evaluate foetal left ventricular performance when its preload was increased by banding the pulmonary artery, a study design where a simultaneous change in left ventricular afterload is unlikely.

Nine ovine foetuses were studied with real-time images and Doppler echocardiography before, 3-4 and 6-8 d after surgery. Seven of these foetuses were also studied during the surgical intervention, immediately before and within 2 min after banding.

The immediate effects of a 90-95% reduction of the pulmonary artery cross-sectional area were: a 53 +/- 20% (mean +/- SD) decrease and a 38 +/- 10% increase of right (RvQ) and left ventricular output (LvQ), respectively. Comparing measurements before and 3-4 d after operation, there was a 64 +/- 16% decrease of RvQ and a 64 +/- 25% increase of LvQ. The increase in LvQ was due to an increase in both heart rate (19 +/- 10%) and stroke volume (38 +/- 18%). After an additional 3-4 postoperative days, heart rate remained increased to the same extent, but there was a more pronounced increase of LvQ (93 +/- 19%) and stroke volume (59 +/- 22%).

The parallel foetal circulation has a capacity to handle a severely increased afterload for the right ventricle by immediately improving and maintaining an increased left ventricular performance. This improvement was in part accomplished by an increase in stroke volume.