ECHOCARDIOGRAPHIC PREDICTORS OF LEFT-VENTRICULAR OUTFLOW TRACT OBSTRUCTION AFTER REPAIR OF INTERRUPTED AORTIC-ARCH

Objectives. This study was designed to identify preoperative echocardi ographic predictors of left ventricular outflow tract obstruction afte r repair of interrupted aortic arch and ventricular septel defect clos ure. Background. Left ventricular outflow tract obstruction becomes ap parent in nearly 50% of patients after repair of interrupted aortic ar ch and ventricular septal defect closure but is seldom recognized preo peratively. Methods. We analyzed the preoperative echocardiograms of a ll patients with interrupted aortic arch who had postoperative echocar diographic or catheterization data available. Thirty-seven infants (ag ed 1 day to 10 months, median 5 days) were included. Off-line measurem ents were performed on hard copies of selected images. The cross-secti onal area (indexed to body surface area) and diameters (indexed to the square root of body surface area) of the left ventricular outflow tra ct; ascending and descending aorta; ventricular septal defect; and mit ral, aortic and pulmonary valves were compared with outcome by using a nalysis of variance. Outcome was classified according to development o f postoperative left ventricular outflow tract Doppler gradient (Group 1 less than or equal to 20 mm Hg, Group 2 > 20 mm Hg). Results. The c ross-sectional area of the left ventricular outflow tract was signific antly smaller in patients who did than in those who did not develop su baortic obstruction ([mean +/- SD] 0.64 +/- 0.25 vs. 1.7 +/- 1.01 cm(2 )/m(2), p < 0.004). Left ventricular outflow tract and aortic valve di ameters and aortic valve area were not predictive of postoperative lef t ventricular outflow tract obstruction. Incidence of postoperative le ft ventricular outflow tract obstruction was lower (p < 0.03) in inter rupted aortic arch type A (0 of 6) than in type B (15 of 31). The inci dence of aberrant right subclavian artery was lower (p < 0.02) in Grou p 1 (6 of 22) than in Group 2 (10 of 15). Conclusions. The preoperativ ely measured cross-sectional area of the left ventricular outflow trac t is significantly smaller in patients with interrupted aortic arch wh o develop subaortic obstruction postoperatively, with a left ventricul ar outflow tract area less than or equal to 0.7 cm(2)/m(2) being a sen sitive predictor. Aortic arch anatomy (i.e., type of interrupted aorti c arch and presence of aberrant right subclavian artery) is also predi ctive of postoperative left ventricular outflow tract obstruction, pos sibly by influencing the volume of blood flow across the left ventricu lar outflow tract. These data should enable preoperative identificatio n of infants who may require surgical relief of subaortic stenosis.