Critical left ventricular outflow tract obstruction: The disproportionate impact of biventricular repair in borderline cases.

OBJECTIVE: In critical left ventricular outflow tract obstruction, the common perception that biventricular physiology is superior to univentricular physiology has led to a bias favoring biventricular repair. We hypothesized that pursuit of biventricular repair in borderline candidates increases mortality.
METHODS: Between 1994 and 2001, 362 neonates with critical left ventricular outflow tract obstruction were prospectively enrolled by 26 institutions. Initial procedure indicated intended univentricular repair (n = 223; 84 deaths) or biventricular repair (n = 139; 39 deaths). Parametric risk-hazard analysis identified predictors of death for univentricular and for biventricular repair, which allowed prediction of the 5-year univentricular survival advantage for every infant. Survival was scrutinized for children managed discordantly to univentricular survival advantage predictions.
RESULTS: Incremental factors for death after univentricular repair were as follows: tricuspid regurgitation, smaller mitral annulus z-score, smaller indexed dominant ventricular length, and presence of a large ventricular septal defect; risk factors after biventricular repair were as follows: minimum left ventricular outflow tract diameter, endocardial fibroelastosis, left ventricular dysfunction, and smaller mid-aortic arch. These variables formed the univentricular survival advantage tool (all P < .0001, R(2) = 0.92). Discordant management was more common with biventricular than with univentricular repair (56% vs 21%; P < .01). Discordant pursuit of biventricular repair was associated with significantly more observed versus expected deaths (biventricular repair 30 vs 14; P < .001; univentricular repair 20 vs 13; P = .02). Survival after biventricular repair is sensitive to changes in univentricular survival advantage values, especially in borderline candidates. In contrast, univentricular repair survival is insensitive to changes in univentricular survival advantage values.
CONCLUSIONS: Inappropriate pursuit of biventricular repair in borderline candidates is more frequent and more consequential in survival terms than is inappropriate pursuit of univentricular repair. Use of the univentricular survival advantage tool will help identify infants for whom univentricular repair may be a better choice than attempting biventricular repair.