BACKGROUND: The extra-cardiac conduit Fontan (EC) has a lower incidence of tachyarrhythmias than other types of Fontan. However, some intrinsic arrhythmogenic conditions, such as atrial isomerism, have been associated with a high incidence of arrhythmias. METHODS AND RESULTS: We retrospectively reviewed the clinical course of the supraventricular tachyarrhythmias (SVTs) in 212 patients after an EC, compared the results according to the atrial situs and investigated the substrate of the SVTs. The atrial situs was a solitus or inversus (SS/SI) in 152 patients, right isomerism (RI) in 45 and left isomerism (LI) in 15. Twenty-four SVTs occurred in 22 (11%) patients ≥3 months after the EC. The freedom from SVT after the EC was 95%, 76% and 77% in the SS/SI, RI and LI patients at 5 years, respectively (P<0.0001). Among the 16 SVTs associated with atrial isomerism, 10 were not related to the atrioventricular (AV) node. For the atrial isomerism, the predictors of SVT ≥3 months after the EC were a history of an AV valve repair (risk ratio (RR) 1.9; P=0.02) and complications associated with sinus node dysfunction (RR 1.9; P=0.03). Death related to SVT occurred in 3 patients. CONCLUSIONS: Postoperative SVTs after the EC with an atrial isomerism were not uncommon, mostly did not involve the AV node and possibly were caused by atrial tissue damage. A comprehensive therapeutic strategy should be considered.
BACKGROUND: The extra-cardiac conduit Fontan (EC) has a lower incidence of tachyarrhythmias than other types of Fontan. However, some intrinsic arrhythmogenic conditions, such as atrial isomerism, have been associated with a high incidence of arrhythmias. METHODS AND RESULTS: We retrospectively reviewed the clinical course of the supraventricular tachyarrhythmias (SVTs) in 212 patients after an EC, compared the results according to the atrial situs and investigated the substrate of the SVTs. The atrial situs was a solitus or inversus (SS/SI) in 152 patients, right isomerism (RI) in 45 and left isomerism (LI) in 15. Twenty-four SVTs occurred in 22 (11%) patients ≥3 months after the EC. The freedom from SVT after the EC was 95%, 76% and 77% in the SS/SI, RI and LIpatients at 5 years, respectively (P<0.0001). Among the 16 SVTs associated with atrial isomerism, 10 were not related to the atrioventricular (AV) node. For the atrial isomerism, the predictors of SVT ≥3 months after the EC were a history of an AV valve repair (risk ratio (RR) 1.9; P=0.02) and complications associated with sinus node dysfunction (RR 1.9; P=0.03). Death related to SVT occurred in 3 patients. CONCLUSIONS: Postoperative SVTs after the EC with an atrial isomerism were not uncommon, mostly did not involve the AV node and possibly were caused by atrial tissue damage. A comprehensive therapeutic strategy should be considered.