Persistence of collateral circulation after correction of aortic coarctation

The persistence of collateral circulation was evaluated one year after the correction of experimental aortic coarctation (CoA) by assessing renal perfusion with the Xenon 133-washout method and measuring distal aortic blood pressure during cross-clamping of the thoracic aorta. CoA was created in 7 puppies at 2 months of age and was corrected after a follow-up with a venous patch when the dogs were 9 months old. Two of the dogs were lost during the corrective operation due to anaesthetic complications. Four sham-operated dogs served as controls. One year after correction of CoA, four of the dogs had a pressure gradient of less than 5 mmHg at the site of CoA and one a pressure gradient of 15 mmHg. In renal perfusion measurements a mean decrease of 49% and 96% was found in the study and control groups, respectively. Blood pressures in the distal aorta decreased 47% and 83%, respectively. Two dogs in the study group had a distal blood pressure under 50 mmHg and their renal perfusion decreased markedly. Collateral circulation decreased with time after a good anatomic correction of CoA, so that one year after correction of experimental CoA about one half of the initial collateral capacity remained. This suggests that in most reoperations performed at least one year after the primary corrections, temporal shunting or a left side bypass is necessary to ensure sufficient circulation in the distal organs.