Background: The predictors of left ventricular outflow tract obstruction (LVOTO) after the repair of coarctation of the aorta or interruption of the aortic arch (CoA/IAA) with ventricular septal defect have been investigated. However, the predictors remain controversial.

Methods: We performed primary repair of CoA/IAA with ventricular septal defect for 75 patients from 1996 to 2005. Four of the 75 patients died within 5 years after primary repair without relation to LVOTO. The morphology of the aortic valve of 71 survivors was bicuspid in 23 patients and tricuspid in 48 patients. The mean follow-up was 9.2 ± 2.6 years after primary repair.

Results: There were 12 patients who showed LVOTO of 3.0 m/s or greater after primary repair. All of the 6 bicuspid patients demonstrated valvular aortic stenosis, and all of the 6 tricuspid patients showed discrete subvalvular LVOTO. In 5 of the 6 tricuspid patients, the aortic annular z-score before primary repair was -3.0 or less. A bicuspid aortic valve (p = 0.016) and the aortic annular z-score of -3.0 or less (p = 0.019) were significant risk factors for LVOTO after primary repair. At 10 years after primary repair, 82.6% and 95.6% of the bicuspid and tricuspid patients, respectively, were free from reoperation (p = 0.015).

Conclusions: The presence of a bicuspid aortic valve and an aortic valve annular z-score of -3.0 or less before primary repair are risk factors for LVOTO, and stenotic bicuspid valves and discrete subvalvular LVOTO are the main causes of LVOTO after primary repair of CoA/IAA with ventricular septal defect. The bicuspid patients more frequently required reoperation than the tricuspid patients.