Analysis by mathematical model of haemodynamic data in the failing Fontan circulation

Several late complications jeopardize the clinical performance of recipient s of the Fontan operation. The underlying causes have been referred to dist urbed flow dynamics in the cavopulmonary connections. Presumably, the large pressure drops occurring in the inferior and superior connections play a p ivotal role in the pressure level of the entire circulation, especially in the venous. To address this issue, we retrospectively reviewed catheterizat ion data of six patients with failing Fontan circulation and compared them with those of six patients with functioning Fontan circulation. The impact on the systemic and pulmonary pressure of the increase in the cavopulmonary connection resistances was studied through a steady-state mathematical mod el of the univentricular closed-loop circulation. In the patients with fail ing Fontan, pressure in the venae cavae was found to be significantly highe r, especially at the inferior cava (19.3 +/- 2.2 versus 12.5 +/- 2.3 mmHg) with the pressure drop at the inferior cavopulmonary connection significant ly increased (4.7 +/- 3.1 versus 0.33 +/- 0.82 mmHg). The proposed mathemat ical model permits us to clearly relate the pressure increase in the venae cavae to an increased resistance in the cavopulmonary connections. Therefor e, the present analysis confirms that, to avoid possible congestion of veno us circulation, the definitive palliation of univentricular heart should no t cause pressure drops at the cavopulmonary connections.