Pulmonary arteriovenous malformations after cavopulmonary anastomosis.

Pulmonary arteriovenous malformation (PAVM) is common after cavopulmonary anastomosis. PAVMs appear on chest X-ray film as diffuse opacity in one or both lungs. Angiographically, it appears as spidery diffuse vascularity with near simultaneous opacification of pulmonary arteries and veins.

We present images of pulmonary arteriovenous malformation (PAVM) in a 6-year-old child after cavopulmonary anastomosis. The right pulmonary angiogram shows extensive and diffuse spidery PAVMs [Figure 1a] in the right lower lobe. The pulmonary artery and vein are seen to opacify almost simultaneously. The left pulmonary angiogram shows normal pulmonary arborization with no PAVMs [Figure 1b]. A chest skiagram shows diffuse opacification in the right lower lobe [Figure 2].

Figure 1

(a) Right pulmonary angiogram showing spidery PAVMs in the right middle and lower lobe; (b) Left pulmonary angiogram showing normal arborization pattern of the left pulmonary artery in the same patient without PAVMs

Figure 2

A chest X-ray PA view showing diffuse opacification in right middle and lower lobe due to the presence of PAVM

PAVMs are a cause of progressive cyanosis after cavopulmonary anastomosis in children with single ventricle physiology who are on the pathway to a Fontan procedure. Clinically significant PAVMs occur in as many as 25% of patients who are followed for several years after cavopulmonary anastomosis.[1] The exact cause of PAVMs after cavopulmonary anastomosis remains unknown. The absence of pulsatile flow, hepatic factor, and hypoxia are the various reasons cited for the development of PAVMs after cavopulmonary anastomosis. Recent studies suggest a key role of the liver in the development of these lesions.[2] PAVMs develop whenever hepatic venous effluent does not perfuse the pulmonary arteries directly either on a congenital basis or postoperatively.[3‐5] The liver is known to produce precursors of angiogenesis inhibitors. Collagen XVIII and plasminogen are produced in large quantities by the liver and secreted into hepatic venous effluent where subsequent action by proteolytic enzymes cleaves these precursors into the potent angiogenesis inhibitors endostatin and angiostatin, respectively. Exclusion of these substances from the pulmonary arterial circulation after cavopulmonary anastomosis may result in vascular proliferation that would normally be held in check.[67]

Chest X-ray shows spidery pulmonary blood vessels distributed evenly throughout both lungs. The diagnosis is confirmed by pulmonary angiography; the central and the middle sized arteries are dilated and untapered, filling a myriad of spidery small branches that extend far into the periphery of the lung with evidence of right-to-left shunting demonstrated by the rapid appearance of contrast in the pulmonary veins after pulmonary artery injection. Contrast echocardiography is considerably more sensitive than angiography for detecting this condition. It shows the early appearance of micro bubbles in the pulmonary venous atrium after peripheral venous injection of agitated saline. When used as a screening tool, contrast echocardiography detects intrapulmonary right-to-left shunting in a large percentage of children after cavopulmonary anastomosis, even in the absence of clinically evident PAVMs.[78]