INTRODUCTION: The Fontan procedure is an anatomically complex cardiac revision performed in children with univentricular congenital heart diseases, including tricuspid atresia. The surgery has undergone multiple revisions since its inception by Dr. Francis Fontan in 1971, with a resulting evolution in its complication profile. We present the case of a 23-year-old female who presents with a well-known and life-threatening complication of the Fontan procedure.
CASE PRESENTATION: K.L. is a 23 yo female who presented to clinic with 1 week of SOB and palpitations. Shortly after birth, she was found to have tricuspid atresia. She underwent a Blalock-Taussig shunt at 6 weeks of age. At age 4, she underwent a Fontan procedure with right atrial to pulmonary artery anastomosis and ligation of the BT shunt. Her post-Fontan history was complicated by atrial tachyarrhythmias that were treated medically. On presentation, the patient appears uncomfortable and tachypneic. Her lungs are clear and her cardiac exam reveals an irregular tachycardia with no JVD, gallop, or RV heave. She required high-flow oxygen to maintain normal oxygenation. EKG revealed atrial tachycardia with a 2:1 AV block. An urgent TEE for planned cardioversion showed a 3 cm X 2 cm right atrial thrombus. A followup CTA revealed bilateral lobar and segmental acute pulmonary emboli. She was started on a high-dose heparin drip and given two courses of systemic TPA, the second initiated after the patient developed worsening hypoxia and a bedside TTE showed disruption of the right atrial clot with downstream embolization. The patient also underwent direct infusion of TPA into the right atrium for 60 hours. Given the dependence of the Fontan circuit on low pulmonary artery pressures, the patient was started on sildenafil and inhaled nitric oxide. By discharge, CTA showed a significant decrease in clot burden, TEE showed resolution of the right atrial thrombus, and the patient was not hypoxemic. The patient was discharged on coumadin, enoxaparin, and sildenafil 30 mg tid. She was referred for a Fontan revision to an extracardiac conduit with Maze procedure.
DISCUSSIONS: Our patient's complex cardiac history began when she was born with tricuspid atresia. a univentricular system with parallel systemic and pulmonary circulations. The Blalock-Taussig shunt is a palliative procedure that manufactures a shunt between the subclavian and pulmonary arteries to divert more blood to the lungs for oxygenation. This intervention is commonly performed as a bridge to the Fontan procedure that is usually delayed until later in life to allow reduction of pulmonary vascular resistance and enlarging of the vena cava. The classic Fontan procedure creates a communication between the pulmonary artery and the right atrium, effectively bypassing the right ventricle altogether and allowing the systemic venous circulation to flow directly into the pulmonary arterial system. A more updated version of the Fontan is the total cavopulmonary connection, which is a 2-stage operation that connects the caval circulation directly to the pulmonary artery, bypassing both the right atrium and the right ventricle. The cavopulomonary connection evolved out of an understanding of some of the common complications of the classic Fontan procedure, including atrial arrhythmias and cardiac thrombus with pulmonary embolism. The atrial arrhythmias are attributed to postsurgical scarring and sinus node injury, and have been shown to have low recurrence rates in Fontan patients who undergo conversion to the cavopulmonary Fontan with atrial arrhythmia surgery (cryoablation vs Maze). Cardiac thromboemboli have been attributed to a low-flow state and atrial arrhythmias. Decreasing the incidence of atrial arrhythmias, and bypassing both the right atrium and right ventricle should theoretically decrease the incidence of cardiac thrombotic events, although further studies are still necessary.
CONCLUSION: This case demonstrates the creativity required to manage complex and hemodynamically sensitive post-Fontan patients with life-threatening complications.
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