Growth of left heart structures following the hybrid procedure for borderline hypoplastic left heart

The 'hybrid' procedure is an alternative to the Norwood operation in classical hypoplastic left heart syndrome to support the systemic circulation until subsequent palliation. This approach has been extended to infants with the borderline development of left heart structures. We investigated whether or not a hybrid procedure for 'borderline' cases of underdevelopment of the left heart would lead to any improvement in the growth of those structures relative to body size or would impact on eventual repair. Serial echocardiograms were reviewed in cases in whom left heart development was judged borderline for adequacy to support the systemic circulation. z-scores of left heart structures and aortic discriminant scores were plotted sequentially following the hybrid procedure and random-coefficient linear-mixed models were applied to quantify growth rates. Seven infants met the inclusion criteria. At birth, the median (range) of aortic discriminant scores was -2.67 (-3.26 to -1.22), suggesting that a biventricular repair would not be feasible. Following a hybrid procedure, aortic discriminant scores increased with time and three infants were managed with a biventricular repair. The rate of change was significantly higher in infants who achieved a biventricular repair compared with those who did not (P = 0.01). The hybrid procedure allows time for growth of left heart structures in selected infants, and serial echocardiography may assist in identifying those children who may ultimately achieve a biventricular circulation.