Despite excellent results of repair of the balanced AVSD, there are no criteria to judge adequacy of the LV for biventricular (BiV) repair in the severely unbalanced AVSD. We hypothesized that feasibility for BiV repair depends largely on ventricular geometry because of right ventricular (RV) volume loading; that is, despite a small true pre-op LV volume,potential LV volume may allow BiV repair, as predicted from pre-op LV dimensions. The echocardiograms of 5 recent consecutive patients with right-dominant AVSD, all of whom underwent BiV repair, were retrospectively reviewed. Median age of AVSD repair was 3 mos (23 days to 5 mos). All patients had an adequate LV, aortic annulus, and aortic arch to support the systemic circulation post-operatively (post-op), with 1 inhospital death. LV volume was estimated by the method of Rhodes et al. (Circulation 1991; 84:2325). Measurements showed severe LV hypoplasia pre-op, with an RV-forming apex in all cases; 3 patients had true LV volumes <10 ml/M2. Potential LV area derived from short-axis measurements just below the AV valve was defined as twice the area bounded by the posterior endocardial LV surface and a theoretical line drawn from one end of the crescent-shaped LV to the other end. Potential pre-op LV volumes ranged from 14.78 - 61.90 ml/M2 (mean 32.04 ± 18.82). All patients post-op had true volumes >30 ml/M2. Pre-op potential volume and post-op true volume correlated well (post-op true=1.54 pre-op potential- 0.735 ml; r=0.88, p<0.05) with, as expected, worse correlation between pre-op and post-op true volumes (r=0.70, p=0.19). Increases in LV length and mitral annulus size indicated contributions of volume loading and surgical patching to the increase in LV size. In summary, BiV repair can be achieved in the severely unbalanced AVSD. In this small series, pre-op potential LV volume≥15 ml/M2 allowed BiV repair, while true pre-op volumes would have predicted an inadequate LV in most cases. This study has broad implications for this and other right-sided volume-loaded lesions in which the LV initially is judged to be hypoplastic but in which BiV repair may be feasible.Table

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