Ductus arteriosus wave intensity analysis in fetal lambs: midsystolic ductal flow augmentation is due to antegrade pulmonary arterial wave transmission.
In midsystole, fetal pulmonary trunk (PT) and arterial (PA) blood flows characteristically fall, despite pulmonary blood pressure increasing, while ductus arteriosus (DA) flow continues to rise to a delayed peak. Wave intensity (WI) analysis indicates that midsystolic fetal PT and PA flow reductions are related to a very large midsystolic PA backward-running compression wave (BCW(ms)), which originates in the pulmonary microvasculature and is partially transmitted into the PT. This study tested the hypothesis that midsystolic augmentation of DA blood flow was related to transmission of the PA BCW(ms) into the DA. DA, PT, and PA WI analysis was performed in eight anesthetized late-gestation fetal sheep instrumented with DA, PT, and left PA micromanometer catheters to measure pressure (P) and transit-time flow probes to obtain blood velocity (U). In a subgroup (n = 5), the main PA was briefly occluded to abolish wave transmission from the lungs. WI was calculated as the product of P and U rates of change. PA and PT WI profiles both contained a prominent BCW(ms), approximately 5-fold larger in the PA (P < 0.005), which increased P but decreased U. By contrast, the DA WI profile demonstrated a large midsystolic forward-running compression wave (FCW(ms)), which increased DA P and U, and occurred 5 ms after PA BCW(ms). Furthermore, both DA FCW(ms) and PT BCW(ms) were abolished by main PA occlusion. These results suggest that the fetal PA BCW(ms) undergoes retrograde transmission into the PT as a BCW(ms), but antegrade transmission into the DA as a FCW(ms) that augments midsystolic DA flow.
Smolich
Joseph J
JJ
Department of Paediatrics, Heart Research Group, Murdoch Children's Research Institute, University of Melbourne, Melbourne, Australia. joe.smolich@mcri.edu.au
Mynard
Jonathan P
JP
Penny
Daniel J
DJ
D000818:Animals; D001783:Blood Flow Velocity; D001794:Blood Pressure; D002245:Carbon Dioxide / Q000097:blood; D003326:Coronary Circulation; D004373:Ductus Arteriosus / Q000000981:diagnostic imaging / Q000502:physiology*; D015150:Echocardiography, Doppler; D005260:Female; D005312:Fetal Blood / Q000378:metabolism; D005865:Gestational Age; D006863:Hydrogen-Ion Concentration; D010100:Oxygen / Q000097:blood; D011247:Pregnancy; D011651:Pulmonary Artery / Q000000981:diagnostic imaging / Q000196:embryology / Q000502:physiology*; D011652:Pulmonary Circulation; D012039:Regional Blood Flow; D012756:Sheep
D002245:Carbon Dioxide; D010100:Oxygen