We evaluated the physical characteristics of the pulmonary trunk in 32 patients with complete transposition after the arterial switch operation, calculating the pulmonary input impedance. In 6 of the patients, the characteristic impedance was equal to, or less than, the value in patients with ventricular septal defect. In those patients with an intact ventricular septum, or those with a ventricular septal defect who had undergone the arterial switch operation or banding of the pulmonary trunk before 3 months age, the frequency of the first modulus minimum also agreed with the values obtained in patients with ventricular septal defect. The value was high, however, in patients with complete transposition with ventricular septal defect who had undergone an arterial switch operation or banding of the pulmonary trunk after 4 months of age. Our data suggest decreased distensibility of the proximal pulmonary trunk after the arterial switch operation, and mild changes in the pulmonary vasculature in patients with complete transposition with ventricular septal defect who had undergone either an arterial switch operation or banding of the pulmonary trunk after 4 months of age. Long-term follow-up is needed clarify whether or not these features affect right ventricular function by means of an increase in afterload.

Accurate bedside assessment of the ratio of pulmonary to systemic flow (Qp/Qs ratio, referred to as “the flow ratio” or “the ratio”) plays an important role in the management of many congenital heart defects, especially the complexes unified by univentricular atrioventricular connections. Arterial oxygen saturation can be a misleading measure of the ratio, and may not reflect derangements until they are quite large. Theoretical analysis suggests that systemic venous oxygenation may be a better indicator of the ratio. To examine this, we created a widely patent atrial septal defect in neonatal piglets (weight =4–6.5 kg, n=6). Snares aruond the aorta and pulmonary trunk were adjusted to alter the flow ratio from 0.1 to 6.5. Venous oxygen saturations, measured in the mid-inferior caval vein, were at a maximum at a ratio about 1, and declined rapidly with increases or decreases in the ratio beyond a limited range. The venous oxygen saturation was found to vary much more than arterial oxygen saturation, with arterial oxygen saturation only falling when the ratio dropped below 0.5. Oxygen delivery (Oxygen Content x Cardiacoutput) was found to parallel closely systemic venous oxygen saturation, and was at a maximum at the same ratio that produced a maximum value of systemic venous oxygen saturation. The study suggests that systemic venous oxygen saturation provides a better estimate than does systemic arterial oxygen saturationof the flow ratio and oxygen delivery. Interventions that maximize systemic venous oxygen saturation should maximize oxygen delivery, and determination of systemic venous oxygen saturation should be a helpful addition in managing children with a number of congenital heart defects.

Background: We sought to determine if the acute gains in pulmonary arterial diameter achieved by using Cutting Balloons to dilate stenoses in small arteries are maintained at follow-up. Methods: A search of our database identified all patients who underwent dilation with Cutting Balloons for pulmonary arterial stenosis between June 2001 and September 2003. We reviewed the procedural and angiographic data obtained at the initial and follow-up procedures. Results: Over the period of study, 29 patients with a median age of 3.7 years, and a range from 0.4 to 46.6, underwent treatment with Cutting Balloons at 41 procedures for one or more pulmonary arterial obstructions resistant to conventional angioplasty. At the initial procedure, we enlarged 79 vessels, with an initial minimal luminal diameter of 1.5 plus or minus 0.8 millimetres, to a diameter of 3.0 plus or minus 1.1 millimetres (p smaller than 0.001). Angiographic data indicated that 49% of the vessels showed evidence of vascular damage not requiring intervention, while stents were placed in 9 vessels. Follow-up angiography was available for 39 of the vessels, evaluated at a median of 6 months, with a range from 3 to 24 months, after the initial procedure. In these vessels, there was a mean loss of 10 plus or minus 25% in luminal diameter, p not significant. Of the 39 vessels, 8 had returned to a diameter within half of the initial diameter, giving a failure rate at follow-up of 21%, with 95% confidence intervals from 9% to 36%. All complications were identified within 24 hours of the catheterization procedure, and there were no late complications or deaths during the period of follow-up. Placement of stents produced both greater increases in diameter at the initial procedure (p smaller than 0.001), and greater losses at follow-up (p equal to 0.01). Conclusions: Despite the frequent identification of intravascular trauma, initial gains in luminal diameter after use of Cutting Balloons to dilate stenotic pulmonary arteries are maintained at follow-up.