Andersons pediatric cardiology 1863

FIG 71.12 The lateral tunnel Fontan constructed after a prior hemiFontan (A) The functioning hemi-Fontan showing the intact patch between the superior cavopulmonary anastomosis and the right atrium (B) An atriotomy is performed and the patch between the superior cavopulmonary anastomosis and the right atrium is excised (C) A baffle created by incising a tube graft longitudinally is sewn in place to direct blood from the inferior caval vein to the pulmonary arteries (From Jacobs ML, Pourmoghadam KK The hemi-Fontan operation Semin Thorac Cardiovasc Surg Pediatr Card Surg Annu 2003;6:90–97.) Potential advantages of the lateral tunnel Fontan include growth potential and ease of fenestration Computational fluid dynamic studies suggest better efficiency with lower energy loss.268 The disadvantages of the lateral tunnel include the need for aortic cross clamping and the inclusion of prosthetic (potentially thrombogenic) material exposed to the pulmonary venous atrium, which could increase the risk of stroke and sinus node dysfunction In contrast, the extracardiac Fontan may have less arrhythmias, does not require cross clamping, and, with ideal anatomy, can even be done without cardiopulmonary bypass The disadvantages include the lack of growth potential, neointimal proliferation with obstruction, and thrombus formation Large single-center series show comparable outcomes with both types of completion Fontan.256,269–276 The choice appears to be largely institutional, although the extracardiac Fontan appears to be gaining in popularity due to ease of construction and application to a wide variety of anatomic variations One area where the extracardiac Fontan has been widely applied is in the setting of apicocaval juxtaposition This occurs when the apex of the ventricular mass sits over the ipsilateral entrance of the inferior caval vein into the atrium rather than the more typical situation in which the apex points contralateral to the inferior caval vein Among patients with fUVH this can complicate construction of the Fontan The choice is whether to bring the conduit along the shortest route, behind the ventricular mass, which risks compression of the conduit, or to bring the conduit across the midline, over the vertebral column.277–280 A third option is the intra/extracardiac Fontan, which may be suitable to complex including apicocaval juxtaposition (Fig 71.13) With this approach, through an atriotomy, a conduit is anastomosed to the entrance of the inferior caval vein The conduit runs through the atrium before exiting the roof and continuing to the pulmonary arteries.212 This technique can be applied to a wide variety of anatomic variations and a fenestration to create within the intraatrial portion of the conduit is straightforward FIG 71.13 Intra/extracardiac Fontan (A) An atriotomy is created away from the sinus node (B) A tube graft is anastomosed to the inferior caval vein orifice A fenestration is created in the tube graft that will be contained in the atrium The tube graft exits the atrium via the atriotomy, which is then sewn to the graft to close the atrium (C) The cephalad end of the graft is then anastomosed to the pulmonary arteries ePTFE, Expanded polytetrafluoroethylene (From Jonas RA The intra/extracardiac conduit Semin Thorac Cardiovasc Surg Pediatr Card Surg Annu 2011;14:11–18.) A fenestration is an intentional defect created within the Fontan pathway that connects it to the pulmonary venous atrium The fenestration will shunt right to left, lowering central venous pressure and augmenting ventricular preload, albeit at the expense of some degree of desaturation As a consequence of surgery and cardiopulmonary bypass, all patients in the early postoperative period will experience a transient period of increased PVR A fenestration may be most beneficial in the early postoperative period The combination of lower central venous pressure and increased ventricular preload will improve systemic output and the lower central venous pressure, reducing hydraulic factors leading to persistent pleural effusions In a randomized controlled trial, the use of a fenestration resulted in shorter duration of chest tube output and hospital length of stay.281 A persistent fenestration has risk and benefits In addition to incomplete relief of hypoxemia, a fenestration can result in paradoxic embolism and stroke, although there are as yet insufficient data to suggest that fenestration closure reduces stroke risk in this patient population.282–284 Fenestration has been used as a strategy to manage late complications of the Fontan, including protein-losing enteropathy and plastic bronchitis; therefore a persistent fenestration may be worth maintaining In a retrospective analysis, fenestration closure was associated with improved saturation but not improved event-free survival.285 Decision Making: When Is It Safe to Leave the Operating Room? At the completion of an uncomplicated Fontan procedure, central venous pressure will be elevated in the high teens and saturations should be greater than 90% in those patients without a fenestration and greater than 80% among those with a fenestration Prior to weaning from cardiopulmonary bypass, the team should make certain that ventilation is satisfactory and that electrolytes, particularly calcium, have been normalized Low to moderate inotropic support is common and milrinone is commonly used as a first-line inotropic agent due to its pulmonary vasodilatory action Transesophageal echo should be performed prior to weaning from bypass to make certain that de-airing is complete and after weaning from bypass to make certain that ventricular function is satisfactory and that any residual AV valve regurgitation is acceptable Low cardiac output in the face of an elevated central venous pressure suggests a problem with the Fontan pathway or an elevation of PVR The pulmonary venous atrial pressure can be