EARLY CHANGES IN VENTRICULAR SEPTAL-DEFECT SIZE AND VENTRICULAR GEOMETRY IN THE SINGLE LEFT-VENTRICLE AFTER VOLUME-UNLOADING SURGERY

Objectives. This study investigated the phenomenon of, and the relatio n between, alterations in ventricular geometry after acute surgical vo lume unloading of the ventricle and the development of subaortic steno sis in patients with a single ventricle and ventricular septal defect- dependent systemic flow. Background. Subaortic outflow obstruction has been observed to occur in patients with a single left ventricle after placement of a pulmonary artery band. The timing and etiology of this phenomenon are not well defined. Methods. The preoperative and postop erative echocardiograms of 18 patients 14.9 +/- 22.8 months old (mean +/- SD) with a diagnosis of single left ventricle who underwent pulmon ary artery banding or cavopulmonary connection were reviewed. Postoper ative studies were performed a mean of 7.0 +/- 6.5 days after operatio n. The ventricular septal defect diameter was measured in two orthogon al views and the area calculated using the formula for an ellipse. Int erventricular septal and posterior wall thickness and left ventricular diameter and length were also measured. Results. Mean ventricular sep tal defect area indexed to body surface area diminished by 36 +/- 23% (3.1 +/- 2.7 to 2.0 +/- 1.8 cm(2)/m(2), p < 0.01). Mean interventricul ar septal and posterior wall thickness increased significantly, and le ft ventricular diameter and length decreased significantly. A greater diminution in ventricular septal defect area was noted after cavopulmo nary connection (41 +/- 19%, p < 0.01) than after pulmonary artery ban ding (25 +/- 28%, p = 0.22). Conclusions. In the single left ventricle , diminution in ventricular septal defect size occurs early and is rel ated to an acute alteration in ventricular geometry that accompanies t he decrease in ventricular volume. Ventricular septal defect diminutio n was greater after volume unloading of the ventricle after cavopulmon ary connection than after pulmonary artery banding.