Radionuclide evaluation of ventricular function at rest and during exercise in double inlet ventricle

We studied ventricular volumes and ejection fraction by radionuclide angiography (equilibrium technique) in 15 patients (aged 3–48 years) with double inlet ventricle not yet submitted to corrective surgery. The end-diastolic volume (measured in nine cases) ranged from 108 to 219 ml/m2 (156 ± 32), being lower than the normal theoretical value (right plus left ventricle) in six cases. Ejection fraction ranged from 30 to 77% (56.4 ± 13). The value was significantly higher in the subgroup of 10 patients with a dominant left ventricle as compared to the five cases with dominant right or indeterminate ventricular morphology (63.2 ± 8.3 versus 42.8 ± 9, P < 0.01). In seven of the 15 patients, measurements were obtained both at rest and during dynamic exercise in the semi-upright position. The end-diastolic and end-systolic volumes, stroke volume, ejection fraction underwent a slight non-significant reduction (from 158 ± 29 to 147 ± 24 ml/m2, from 58 ± 16 to 56 ± 24 ml/m2, from 100 ± 27 to 90 ± 24 ml/m2, from 64% ± 9 to 61% ± 13). During exercise, ventricular volumes mostly behaved as follows: slight reduction of end-systolic volume, decrease of end-diastolic volume, no increase (no change or decrease) of ejection fraction. In the small group studied, we can conclude that: end-diastolic ventricular volume varies considerably; basal ejection fraction is significantly lower when the ventricular morphology is of right or indeterminate type; in most patients with double inlet left ventricle, the ejection fraction is normal at rest but does not increase during dynamic exercise; during effort no recruitment of pre-load reserve (Frank-Starling mechanism) takes place and this partly accounts for the abnormal behaviour of ejection fraction.