CASE REPORT Effect of Transcatheter Occlusion of a Pulmonary Arteriovenous Fistula on the Cardiopulmonary Response to Exercise Jonathan Rhodes • Phyllis Pollack • Peter Lang Received: 30 July 2009 / Accepted: 28 September 2009 / Published online: 20 October 2009 Ó Springer Science+Business Media, LLC 2009 Serial exercise testing has demonstrated that transcatheter closure of Fontan fenestrations produces some remarkable alterations in the cardiopulmonary response to exercise. Specifically, in addition to improving oxygen saturations at rest and during exercise, fenestration closure has been found to reduce the minute ventilation/carbon dioxide production relationship slope (VE/VCO 2 slope), raise the end-tidal pCO 2 , and lower the end-tidal pO 2 during exer- cise. These changes reflect more efficient gas exchange after elimination of the right-to-left intracardiac shunt. In these patients, fenestration closure has not, however, been associated with an improvement in the oxygen consump- tion (VO 2 ) at peak exercise [4]. An isolated pulmonary arteriovenous fistula (PAVF) is a rare congenital defect [3, 8] with an obligate right-to-left shunt analogous to that encountered in Fontan patients with patent fenestrations. Surgical [3] and transcatheter [5, 6] techniques for closing PAVFs have been developed recently. Although past studies have reported that exercise function improves after these procedures [1, 2], these studies have provided only limited data regarding the physiologic consequences of PAVF elimination. In the reported case, we present the results of cardio- pulmonary exercise tests performed before and after transcatheter closure of an isolated pulmonary arteriove- nous fistula (AVF). The manner in which the physiologic consequences of this procedure resemble and differ from those observed among patients who have undergone transcatheter closure of Fontan fenestrations provides some unique insights into the physiologic implications of Fontan palliation. Case Report The patient was a 6-lb, 10-oz product of an uncomplicated 42-week gestation. Her early health was excellent. During her early adolescence, however, ‘‘reactive airway disease’’ developed. At the age of 16 years, her oxygen saturation was noted to decline to approximately 85% with exercise and during exacerbations of her reactive airway disease. The degree of desaturation appeared to be out of proportion to the severity of her acute illness. She was therefore referred for cardiologic evaluation. Her physical examination was notable for a resting oxygen saturation of 88–92%. Mild clubbing also was noted. Her cardiac examination results were normal. Fur- ther evaluations included an echocardiogram with contrast injection, chest computed tomography (CT) scan and car- diac magnetic resonance imaging (MRI). These studies showed a large fistulous connection between the right intermediate pulmonary artery and the right upper pulmonary vein. This connection was about 2 cm long, and its diameter varied from 6 to 13 mm. The right lung received 65% of the total pulmonary blood flow, and two-thirds of the right pulmonary blood flow drained into the right upper lobe pulmonary vein. At cardiopul- monary exercise testing (Table 1), her oxygen saturation fell to 79% at peak exercise. Her peak VO 2 and oxygen pulse at peak exercise were mildly depressed. Her VE/ VCO 2 slope was elevated, and her end-tidal pCO 2 at the ventilatory anaerobic threshold (VAT) was low. J. Rhodes (&) Á P. Lang Department of Cardiology, Children’s Hospital, Boston, MA, USA e-mail: jonathan.rhodes@cardio.chboston.org P. Pollack Department of Pediatric, University of Massachusetts Medical Center, Worcester, MA, USA 123 Pediatr Cardiol (2010) 31:142–143 DOI 10.1007/s00246-009-9556-5