Is there a reversal of pulmonary arteriovenous malformation afternredirection of anomalous hepatic venous flow to the lungs?

July 5, 2005

July 5, 2005

Georghiou GP, Birk E and Vidne BA., Cardiothoracic Registrars (Department of Cardiothoracic Surgery,Children's Medical Center of Israel)

Joel Dunning, Department of Cardiothoracic Surgery,Children's Medical Center of Israel

In [patients with an intrapulmonary shunt accompanying anomalous hepatic venous drainage] does [redirection of the hepatic venous drainage to the lungs] improve [patient hypoxemia]

You are scheduled to perform corrective surgery on a 3-year-old boy with a diagnosis of secundum atrial septal defect (ASD). The child presented with progressive cyanosis of one year's duration accompanied by easy fatigability on exercise. There were no indications of hepatic disease. On physical examination, clubbing was noted. Oxygen saturation was 74% in room air, and hemoglobin was 21 g/dl. Echocardiography demonstrated an interrupted inferior vena cava with azygos continuation to a right superior vena cava and a small secundum ASD. Heart catheterization was performed revealing anomalous drainage of all hepatic veins into the left atrium and a small secundum ASD with no measurable cross shunting. Contrast echocardiography confirmed the presence of a pulmonary arteriovenous malformation. You explain to the boy's father that during surgery you will be diverting the hepatic flow and coronary sinus from the left to the right atrium using an autologous pericardial patch. The father asks if this procedure will improve his child's oxygen saturation and if the child will regain a normal level of activity. You are unable to answer him to your satisfaction and therefore you resolve to check the literature for evidence of regression of intrapulmonary shunts after surgical correction of anomalous hepatic venous drainage.

Medline 1966 to January 2005 using OVID interface.

[exp arteriovenous malformations/OR arteriovenous fistula/OR shunt.mp] and (exp cyanosis/OR hypoxemia.mp]

Our survey of the literature revealed 704 papers among which only 3 case reports of 4 cases of anomalous hepatic venous drainage into the left atrium were similar to our case. Cross-checking the reference lists provided an additional 10 papers with 11 cases. These papers were reviewed in full and are presented in the table. In 7 of the reported cases, the hepatic venous drainage was due to a cardiac surgical shunt procedure; in 2, it was due to unintentional surgical exclusion of the hepatic venous flow from the pulmonary circulation; and in 6, it was congenital.

We suspect that the intrapulmonary shunt in the reported patients was caused by the exclusion of hepatic venous blood from the lungs. Indeed, this process has been amply described in children undergoing Glenn shunt (superior vena cava to right pulmonary artery anastomosis), Fontan procedure (atriopulmonary anastomosis to allow bilateral pulmonary arterial flow), and Kawashima operation for tricuspid atresia, which are associated with a 21% rate of intrapulmonary shunts [Srivastava]. The shunts have been shown to regress when the hepatic venous drainage is diverted back through the pulmonary circulation [Tofeig, Johnson]. Furthermore, intrapulmonary shunt was described in 2 patients with anomalous hepatic venous drainage to the left atrium accompanying the interruption and azygos extension of the inferior vena cava [Lee]; again, the shunt regressed with surgical correction of the anomalous venous drainage. In an earlier report of anomalous hepatic venous drainage into the left atrium, Yee suggested that the malformation involves an abnormal enlargement of the sinus venosus (the precursor of the heart) and preservation of the right subcardinal vein, thus inviting an embryologic explanation.
The putative mechanism underlying the development of intrapulmonary shunts apparently involves the exclusion of a hepatic factor from the pulmonary circulation [Knight, Duncan]. Duncan et al, proposed that this factor may be an inhibitor of endothelial proliferation. This notion was supported by their observation of lakes of dilated, thin-walled vessels and chains of clustered small vessels in the lungs of 2 children with post-cardiac-surgery intrapulmonary shunts. The similar development of intrapulmonary vascular dilatations in patients with hepatopulmonary syndrome, and their reversal after liver transplantation [Lange], invites speculation that nitric oxide is implicated in the vascular changes [Soderman, Fallon]. Further evidence of a humoral mediator in cases of anomalous hepatic venous drainage is provided by the reversal of the intrapulmonary shunt after surgical diversion of the anomalous hepatic venous blood into the pulmonary circulation, in addition to the ipsilateral, single-lung angiographic appearance of the intrapulmonary shunt when hepatic venous blood is excluded from only one lung [Srivastava].

In summary, the prior reports documenting the disappearance of intrapulmonary shunts once the hepatic venous drainage is diverted to the right atrium suggest that exclusion of hepatic venous blood from the lungs can predispose the patient to a reversible intrapulmonary shunt

The presence of an anomalous hepatic venous return accompanied by cyanosis may lead to the development of pulmonary arteriovenous malformations. If surgical redirection of hepatic venous flow to the pulmonary arterial system is possible, it should be undertaken to prevent or treat the pulmonary arteriovenous malformations and their sequelae. With proper repair, intrapulmonary shunts due to pulmonary arterial exclusion of hepatic venous return can be rapidly reversed.

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