A balloon-dilatable pulmonary artery band in the dog. Results at one year.

Increased pulmonary blood flow and pulmonary hypertension are frequent problems in infants with congenital heart disease. Although the use of pulmonary artery banding to limit pulmonary blood flow has decreased, the procedure may still be beneficial in certain forms of complex heart disease. The ability to noninvasively relieve the obstruction caused by the band may significantly reduce later operative complexity or even avoid reoperation entirely. The present study evaluated the effectiveness of a balloon-dilatable pulmonary artery band. Twenty 1-week-old dogs had a band of an absorbable suture material (Vicryl; Ethicon, Inc., Somerville, N.J.) placed around the main pulmonary artery. Eight dogs underwent angioplasty 6 months after band placement and also underwent follow-up catheterizations 3 and 6 months after angioplasty. Balloon angioplasty acutely reduced both the right ventricle-pulmonary artery pressure gradient (from 37 +/- 7 mm Hg to 3 +/- 1 mm Hg, p less than 0.001) and the right ventricular systolic pressure (from 62 +/- 8 mm Hg to 32 +/- 2 mm Hg, p less than 0.01). At follow-up the gradient remained low, measuring 4 +/- 1 mm Hg at 3 months and 3 +/- 1 mm Hg at 6 months. Twelve dogs did not undergo balloon dilatation until 12 months after band placement to determine whether any obstruction persisted and whether the band could be relieved after long-term placement. These 12 dogs had progressive increases in right ventricle-pulmonary artery gradient, from 27 +/- 3 mm Hg at 6 months to 43 +/- 4 mm Hg at 12 months. Ten of these dogs underwent dilation 1 year after pulmonary artery band placement. This dilation significantly reduced the right ventricular outflow tract gradient (from 43 +/- 4 mm Hg to 1 +/- 1 mm Hg, p less than 0.001). The remaining two dogs underwent successful partial dilation of the band 12 months after placement. This study demonstrated that a pulmonary artery band of absorbable suture material maintains effective right ventricular outflow tract obstruction for at least 1 year. Additionally, the effect of the pulmonary band can be successfully and persistently relieved.

A simple method for long-term biliary access in large animals.

A simple method to obtain long-term access to the biliary tree in dogs and pigs is presented. In ten dogs and four pigs, a cholecystectomy was performed, the cystic duct isolated, and a catheter inserted into the cut end of the cystic duct. The catheter was connected to a subcutaneous infusion port, producing a closed, internal system to allow long-term access. The catheter placement was successful in three of the pigs and all of the dogs. Thirty-five cholangiograms were obtained in the 13 subjects by accessing the port with a 20 gauge Huber needle and injecting small amounts (4-10 mL) of contrast under fluoroscopic control. Cholangiograms were obtained up to four months after catheter placement without evidence for catheter failure or surgically induced changes in the biliary tree. This model provides a simple, reliable means to obtain serial cholangiograms in a research setting.

Effects of hepatic arterial yttrium 90 glass microspheres in dogs.

A 22-micron glass microsphere called TheraSphere (Theragenics Corp., Atlanta, GA) has been developed in which yttrium 89 oxide is incorporated into the glass matrix and is activated by neutron bombardment to form the beta-emitting isotope yttrium 90 (Y 90) before using the spheres as radiotherapeutic vehicles. The injection of up to 12 times (on a liver weight basis) the anticipated human dose of nonradioactive TheraSphere into the hepatic arteries of dogs was well tolerated and produced clinically silent alterations within centrolobular areas. The hepatic arterial (HA) injection of radioactive TheraSphere also produced portal changes similar to those observed in humans after external beam therapy. While the extent of damage increased with the delivered dose, radiation exposures in excess of 30,000 cGy did not cause total hepatic necrosis and were compatible with survival. No microspheres distributed to the bone marrow and absolutely no myelosuppression was encountered in any animal. Proposed hepatic exposures to humans of 5000 to 10,000 cGy by means of these microspheres, therefore, would appear to be feasible and tolerable. Radiotherapeutic microsphere administration preceded by regional infusion of a radiosensitizing agent and/or immediately following the redistribution of blood flow toward intrahepatic tumor by vasoactive agents can potentially yield a synergistic, highly selective attack on tumors confined to the liver.