Pulmonary arteriovenous shunting in the normal fetal lung.
OBJECTIVE
We hypothesized that pulmonary arteriovenous shunting (PAVS) is normally present in fetal lungs and that cavopulmonary anastomosis-induced PAVS may represent a return to an earlier morphologic stage of development.


BACKGROUND
The surgical superior cavopulmonary anastomosis is performed as part of the staged Fontan pathway to treat univentricular forms of congenital heart disease; PAVS is a known sequela after superior cavopulmonary anastomosis and may have important clinical consequences. Although the etiology and true morphology of the structures responsible for PAVS are unknown, a leading theory is that PAVS is caused by absence of normal hepatic venous drainage to the pulmonary circulation.


METHODS
To determine whether normal fetal lungs demonstrate PAVS, we performed contrast echocardiograms on 13 fetal lambs, 8 neonatal lambs, 4 juvenile lambs, and 4 adult sheep using a blended mixture of saline and blood injected directly into the proximal pulmonary artery.


RESULTS
Pulmonary arteriovenous shunting was detected by direct epicardial echocardiography in all fetal lambs (n = 13) and neonatal animals studied at one and three days of life (n = 4) and in two of four animals studied at six to nine days of life. Pulmonary arteriovenous shunting was not present in animals studied at four weeks of life (n = 2) and in adult sheep (n = 5).


CONCLUSIONS
These studies demonstrate that PAVS is normally present in late gestation fetal and early neonatal lambs but then disappears during the later neonatal period. Furthermore, these findings suggest that PAVS associated with cavopulmonary anastomosis or other processes affecting the developing pulmonary circulation may represent a return to an earlier morphologic stage of development.
University of Washington School of Medicine, Seattle, Washington 98105-0371, USA. mcmullan@u.washington.edu <mcmullan@u.washington.edu>
David Michael
DM
McMullan
Frank Louis
FL
Hanley
Gordon Alan
GA
Cohen
Michael Alan
MA
Portman
Robert Kirk
RK
Riemer
D000818:Animals; D000831:Animals, Newborn; D001164:Arteriovenous Fistula / Q000503:physiopathology; D004452:Echocardiography / Q000379:methods; D005333:Fetus / Q000502:physiology* / Q000503:physiopathology; D011652:Pulmonary Circulation; D012756:Sheep