Background: Patients with Fontan circulation may have heart failure resulting in atrial fibrillation during the late phase. Inotropic effects to ameliorate hemodynamics on the Fontan circulation are not well understood, especially when in atrial fibrillation. This study was performed to determine whether dobutamine therapy in patients with Fontan circulation has limited effects on improving hemodynamics.
Methods: Lumped computational models (sinus and atrial fibrillation) were used, including biventricular, atriopulmonary connection, and extracardiac total cavopulmonary connection Fontan models. The condition of atrial fibrillation including lack of atrial beat, irregular ventricular contraction, and time-varying elastance for the ventricle was introduced. A different dose of dobutamine was given by varying the elastance of the ventricle, heart rate, and peripheral resistance.
Results: In all models, the cardiac output decreased by 22.5% to 25.8% in atrial fibrillation. At 10 μg · kg-1 · min-1 dobutamine in sinus rhythm, the cardiac output increased by 32.3% in the biventricular model but by only 9.2% (P < .001) and 9.1% (P < .001) in the atriopulmonary connection and total cavopulmonary connection Fontan models, respectively. At 10 μg · kg-1 · min-1 dobutamine in atrial fibrillation, the percent increase in the cardiac output in the Fontan circulation (11.8% increase in atriopulmonary connection, P < .001; and 11.9% increase in total cavopulmonary connection, P < .001) was significantly less than that in the biventricular circulation (32.3% increase).
Conclusions: In the Fontan circulation, atrial fibrillation itself reduced the cardiac output by approximately 25%, and dobutamine had a limited effect on increasing the cardiac output, especially when in atrial fibrillation. Maintaining sinus rhythm in patients with Fontan circulation is very important.
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