Since the Fontan procedure results in low pulsatile pulmonary blood flow similar to that seen in patients with a Glenn shunt, it may also be associated with abnormal distribution of flow to the lower lung lobes and with the development of pulmonary arteriovenous fistulae (PAVF). In 12 patients 0.8 to 4.5 years after Fontan procedure and in 20 patients 0.2 to 18 years after receipt of Glenn shunts we assessed ventilation (with '33Xe) and perfusion (after a peripheral injection of 99mTc-macroaggregated albumin) to compare upper to lower lobe distribution of blood flow with that in a control group. The presence of PAVF was assessed by radionuclide activity in kidneys and the brain and by a twodimensional echocardiographic contrast study. A decreased upper/lower lobe perfusion ratio was noted in 13 of 20 patients with Glenn shunts (65%) and correlated with the time after surgery (p < .05). Despite the shorter follow-up period, two of 12 (16%) patients who had undergone the Fontan procedure also had a decreased upper/lower lobe perfusion ratio, and one of these developed right heart failure. Brain and kidney radionuclide counts above control values were observed in all patients with Glenn shunts and in 11 of 12 patients who had the Fontan operation. However, in only five of 20 (25%) patients with Glenn shunts were PAVF confirmed by the two-dimensional echocardiographic contrast study. Three of the five patients with PAVF had Glenn shunts of long duration. While only two of five patients with PAVF had a decreased upper/lower lobe perfusion ratio at the time of the study, this abnormality may have been present in the other three at an earlier stage. Our data suggest that a decreased ratio of upper/lower lobe perfusion may be one of several factors associated with the development of PAVF after a Glenn shunt. Also, longer follow-up of patients who have had a Fontan procedure will be necessary to determine whether they are also a group at risk. Circulation 72, No. 3, 471-479, 1985 We therefore performed ventilation/perfusion lung scans to determine the distribution of pulmonary blood flow in patients after the Fontan procedure (RA-PA and RA-RV). We assessed the presence of PAVF by the scintigraphic appearance of 99mTc-macroaggregated albumin (MAA) in the brain and kidneys after a peripheral intravenous injection and by two-dimensional echocardiographic contrast studies. Our findings were compared with those obtained in patients with Glenn shunts and in normal subjects.

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