Doppler echocardiographic analysis of flow in the ductus arteriosus of infants with hypoplastic left heart syndrome: relationship of flow patterns to systemic oxygenation and size of interatrial communication.

Excessive pulmonary overcirculation related to imbalance in the pulmonary/systemic vascular resistance ratio contributes to hemodynamic instability in infants with the hypoplastic left heart syndrome. Because the ductus arteriosus bridges the two vascular circuits in this lesion, we studied the Doppler echocardiographic flow patterns in the ductus arteriosus of 50 infants with hypoplastic left heart syndrome to investigate their relationship to the degree of pulmonary blood flow as measured by simultaneously obtained levels of partial pressure of oxygen in arterial blood. The degree of restriction to pulmonary venous egress as determined by size of the interatrial communication was also correlated with ductal flow patterns and partial pressure of oxygen in arterial blood. Biphasic flow was noted in all infants. Mean peak velocity of antegrade flow (pulmonary artery to aorta) was greater than that of retrograde flow (aorta to pulmonary artery) (131 +/- 45 cm/sec versus 54 +/- 15 cm/sec; p < 0.001), mean time of retrograde flow was greater than that of antegrade flow (246 +/- 60 msec versus 174 +/- 28 msec; p < 0.001), and mean velocity-time integral of antegrade flow was greater than that of retrograde flow (13.3 +/- 4.8 cm versus 6.3 +/- 3.4 cm; p < 0.001). The ratio of velocity-time integral of retrograde flow/antegrade flow (a volumetric estimate of diastolic reversal into the pulmonary vascular bed indexed to systemic output) correlated extremely well with partial pressure of oxygen in arterial blood (r = 0.91; p < 0.0001). Categoric size of the interatrial communication (none, n = 2; small [<2 mm], n = 9; moderate [3 to 4 mm], n = 23; and large [>4 mm], n = 16) correlated with partial pressure of oxygen in arterial blood (r = 0.82; p < 0.001); the smaller the interatrial communication the lower the partial pressure of oxygen in arterial blood and velocity-time integral ratio of retrograde/antegrade flow. Doppler flow patterns in the ductus arteriosus of infants with hypoplastic left heart syndrome are reflective of the resistance ratio between the pulmonary and systemic vascular circuits and may be helpful in monitoring the hemodynamics of these infants.