Risk factors for a positive neoaortic arch gradient after stage I palliation for hypoplastic left heart syndrome.

BACKGROUND

Providing unobstructed systemic blood flow is one goal of stage I palliation for hypoplastic left heart syndrome. Although clinically significant obstruction is defined when the arch gradient exceeds 15 mm Hg, any positive gradient constitutes obstruction, which may impair ventricular function. We sought to identify risk factors before stage I palliation that result in a positive neoaortic arch gradient before bidirectional Glenn.

METHODS

Reviewed were 51 neonates who underwent stage I palliation and subsequent bidirectional cavopulmonary anastomosis procedures for hypoplastic left heart syndrome. Echocardiograms before stage I palliation were reviewed for aortic dimensions. Cardiac catheterization before bidirectional cavopulmonary anastomosis determined the aortic arch gradient and degree of right ventricular dysfunction.

RESULTS

Of the 51 patients, 24 (47%) had a negative or absent arch gradient. Patients with a positive gradient had a median gradient of 5 mm Hg (range, 1 to 60 mm Hg). The diameter of the ascending aorta and proximal transverse arch indexed to the descending thoracic aorta (0.5 ± 0.2 vs 0.7 ± 0.4 and 0.4 ± 0.2 vs 0.6 ± 0.2 mm, p = 0.02 and p = 0.01) and lower birth weight (3.1 ± 0.5 vs 3.4 ± 0.4 kg, p = 0.03) were risk factors of a positive neoaortic arch gradient. Further, the degree of arch obstruction was inversely related to the degree of right ventricular function (odds ratio, 1.08; p < 0.01).

CONCLUSIONS

Lower birth weight and a smaller aortic diameter confer a higher risk of developing a positive neoaortic arch gradient, resulting in reduced right ventricular function.