VENTRICULAR-FUNCTION DURING SUPINE BICYCLE EXERCISE IN UNIVENTRICULAR CONNECTION WITH ABSENT RIGHT ATRIOVENTRICULAR CONNECTION

Fourteen patients with univentricular connection, absent right connection (tricuspid valve atresia) and normally related great arteries underwent rest and supine bicycle exercise equilibrium radionuclide blood pool studies. Ejection fraction, heart rate, systemic blood pressure and oxygen saturation (ear oximetry) were measured. There were 6 male and 8 female patients. Mean age +/- standard error of the mean was 14.5 +/- 1.1 years (range 6.3 to 21.1). Eight patients (group I) had systemic to pulmonary shunts placed as palliation 8.2 +/- 2.2 years before study and 6 patients (group II) had caval to pulmonary shunts placed 11.8 +/- 1.6 years previously. Ejection fraction at rest was 54 +/- 2% and an abnormal response to exercise (failure of ejection fraction to increase greater-than-or-equal-to 5% from rest to peak exercise) was found in 9 of 14 patients. When analyzed separately, ejection fraction at rest in group I was higher than in group II; however, this difference disappeared at peak exercise. There was a significant negative correlation between ejection fraction at peak exercise and the interval since palliative surgery, although it was not apparent at rest. These data suggest that ventricular function is compromised during exercise and that abnormal performance is influenced by long-standing volume overload. Importantly, this abnormal state is concealed at rest and the choice of palliative shunting procedure appears to have little effect on normalizing pump performance.