atrium.389 The pediatric and adult congenital electrophysiology society and the Heart Rhythm Society recommend vitamin K antagonists for IART or atrial fibrillation Warfarin is the preferred agent over the newer direct oral anticoagulants (DOACs) such as the direct thrombin inhibitors (dabigatran) or factor Xa inhibitors (rivaroxaban, apixaban, and edoxaban) DOACs are currently not recommended in the Pediatric and Adult Congenital Electrophysiology Society/Heart Rhythm Society guidelines due to the lack of safety and efficacy data in these patients who are prone to liver disease.390 Although there is growing experience with the use of DOACs in the adult congenital population, there remains very little experience in the Fontan population.391 Patients who are not taking any form of thromboembolic prophylaxis appear to be at highest risk of thromboembolic events In the absence of clear indications for anticoagulation, aspirin and vitamin K inhibitors appear to be equally efficacious in reducing thromboembolic events.134,296,392 There is growing interest and experience in testing for aspirin resistance to help guide thromboembolic prophylactic strategy in Fontan patients.393 However, additional studies are needed before the utility of this approach can be recommended Surgical Management of Fontan Failure The surgical management of the failing Fontan circulation is dependent on the underlying etiology of the failure Common problems that may be surgically addressed include pathway obstruction, atrioventricular or semilunar valve regurgitation, bradycardia or absence of sinus rhythm, and atrial arrhythmia In particular, patients with atriopulmonary connections who have arrhythmia and a dilated right atrium may benefit from the Fontan conversion procedure.107 Patients with a “failing Fontan” who are not candidates for any of the aforementioned because of ventricular dysfunction may benefit from heart transplantation (see also Chapter 67).394 Analysis of these patients requires a careful multidisciplinary team approach that includes the cardiac surgeon, interventional cardiologist, electrophysiologist, and the cardiac transplant team Pathway obstruction is most commonly dealt with in the interventional catheterization laboratory with balloon angioplasty and stent placement However, some critical stenosis not responding to these therapies may be addressed by conventional surgical techniques using conduits and/or patch material Patients with sinus bradycardia or junctional rhythm may benefit from dual chamber pacemaker implantation A transsternal approach with placement of atrial and ventricular bipolar steroid-eluting epicardial leads and a pacemaker generator implanted beneath the rectus muscle may be the preferred option in these patients Achieving a paced sinus rhythm can often increase the cardiac output of these patients by 20% to 30% For the patient population with an atriopulmonary Fontan with dilatation of the right atrium and either atrial reentry tachycardia, atrial fibrillation, or both, but with preserved ventricular function, the Fontan conversion operation has been quite successful Conversion to an extracardiac Fontan with arrhythmia surgery (biatrial maze using cryoablation) restores sinus rhythm, improves flow dynamics, and increases cardiac output The operation consists of resection of the enlarged right atrium, creation of an atrial septal defect, biatrial maze with cryoablation, extracardiac Gor-Tex graft from the inferior caval vein to the main pulmonary artery, bidirectional superior caval pulmonary anastomosis, and placement of an epicardial dual chamber antitachycardia pacemaker The final result is illustrated in the completed Fontan conversion picture (Fig 73.28).395 Customized pacemaker therapies will optimize management of the patients following Fontan conversion.396 The largest clinical experience with this procedure is at the Ann & Robert H Lurie Children's Hospital of Chicago, where this type of Fontan conversion has been performed in 147 patients at a median age of 23 years The majority of recent patients have both atrial reentry tachycardia and atrial fibrillation The results of this procedure in properly selected patients are excellent, with an operative mortality of 2.1% and mean length of stay of 13 days Risk factors for cardiac death or transplantation after Fontan conversion include right or indeterminate ventricular morphology, preoperative ascites, or PLE, and a cardiopulmonary bypass time greater than 240 minutes Intermediate-term results are also favorable, with 84% alive and free from transplantation or arrhythmia recurrence at 10 years FIG 73.28 Completed Fontan conversion The right atrium has been reduced in size There are bipolar epicardial pacing leads on the right atrium and the anterior surface of the ventricle A PTFE graft connects the inferior caval vein with the pulmonary artery The pulmonary artery has been patched where the atriopulmonary connection was taken down Finally, there is a bidirectional Glenn (From Backer CL, Deal BJ, Mavroudis C, et al Conversion of the failed Fontan circulation Cardiol Young 2006;16 [suppl 1]:85–91.) The number of patients with an atriopulmonary Fontan is declining, and in survivors, morbidity is increasing over time It is apparent that the Fontan conversion is best done early in the course of Fontan failure and that it is best done in centers with the institutional experience to deal with these complex patients When this is the case, a strategy of surgical conversion at an earlier stage of failure may be associated with better survival free from heart transplantation.397 For example, in a report from the Australia and New Zealand Fontan Registry, a center taking a proactive approach with relatively early Fontan conversion had better results than centers where conversion was delayed At the proactive center, conversion was undertaken at an average of 2.9 years after the first arrhythmia episode and after one cardioversion, whereas the other centers waited an average of 4.5 years and two cardioversions The early conversion center was also the highest volume center Patients at this center had an 86% freedom from death or transplantation at 10 years compared with 51% for those at the other centers (Fig 73.29).398 Patients with end-stage ventricular failure, PLE, plastic bronchitis, ascites, or moderate-to-severe atrioventricular valve regurgitation may require heart transplantation The operative mortality for heart transplantation for patients with a failing Fontan until recently was quite