Early onset of pulmonary vascular obstruction in patients with aortopulmonary transposition and intact ventricular septum.

Of 29 patients with aortopulmonary transposition with intact ventricular septum who underwent cardiac catheterization as neonates, five subsequently developed increased pulmonary vascular resistance at an early age (7 months to 2 1 2 years). The resistance was high in two patients (11.0 and 12.9 units (U)/m-2), moderate in one (5.5 U/m-2) and mild in two (3.6 and 4.6 U/m-2). The two patients with the highest resistances died as a result of the pulmonary vascular obstruction and it was probably a contributing factor in the death of a third patient. The finding of pulmonary vascular obstruction at an early age in five of 29 patients with transposition of the great arteries with intact septa is noteworthy. It assumes even greater significance as the measurement methods tend to underestimate pulmonary vascular resistance. The possible errors in assessing pulmnary vascular resistance and factors possibly contributing to early development of pulmonary vascular obstruction are discussed.