Fontan connections

This illustration demonstrates a classic atriopulmonary Fontan connection (figure A) in a patient with a history of a Blalock-Thomas-Taussig shunt (also commonly called the Blalock-Taussig shunt). The right atrial appendage has been anastomosed to the PA confluence, and the atrial septal defect has been closed. These maneuvers direct venous flow from both of the venae cavae through the right atrium and to the pulmonary vascular bed without the assistance of a ventricular pump. The connection of the main PA to the ventricle has been interrupted to eliminate any residual left-to-right shunting. Figures B and C illustrate modifications of the original Fontan concept. They both utilize a direct, bidirectional anastomosis of the SVC to the right PA and a conduit to connect the IVC to the PA. Figure B shows an example of an intra-atrial conduit connecting the IVC to the PA. This modification may still be used when pulmonary venous or other anomalies complicate the placement/use of an extracardiac conduit. Figure C illustrates the anatomy of a patient with an extracardiac Fontan. A nonvalved conduit completes the connection of the IVC to the PA. This conduit is placed within the pericardial space but outside of the heart itself. This type of connection is preferred because it places all of the patient's native atrial volume under the lowest possible distending pressure. In both the intra-atrial conduit and the extracardiac conduit types, a small fenestration can be placed between the conduit and atrium, allowing for a small, persistent right-to-left atrial shunt. An epicardial pacemaker is generally placed during this conversion procedure; the leads are seen attached to the heart in this schematic.