Asynchronous contraction of the 2 ventricles caused by ventricular pacing after a Fontan-type operation in a patient with a biventricular heart.

We treated a 6-year-old boy who had polysplenia syndrome and tetralogy of Fallot with a small right ventricle (RV), an atrial septal defect, a hemiazygos connection, and bilateral superior vena cava. Because the RV was too small for a biventricular repair to be performed, the patient underwent a total cavopulmonary shunt operation although his heart was biventricular and a pacemaker (VVI) had been implanted for management of the sick sinus syndrome complicated by polysplenia syndrome. After the operation, marked asynchronous contraction was noted between the morphological right and left ventricles and was probably responsible for the low cardiac output noted in this patient. In order to clarify the significance of the asynchronous contraction, we determined the cause of the low cardiac output by studying the time course of the volume changes in the morphological right and left ventricles during a cardiac cycle by using angiograms. In addition, we studied the interventricular flow dynamics by using pulsed-Doppler echocardiography. After a Fontan-type operation is performed on patients with a biventricular heart, the 2 ventricles may not function in perfect coordination when they have to work as 1 unit. These patients are likely to develop cardiac dysfunction due to interventricular to-and-fro flow dynamics. Asynchronous contraction between the 2 ventricles caused by abnormal interventricular conduction impaired the cardiac performance in the present case.