Decreased renal perfusion after correction of experimental coarctation

Hemodynamical changes in coarctation were studied with an experimental model. Coarctation of the thoracic aorta was induced in seven puppies at the age of 8 wk. After a 7-month follow-up period a corrective operation with a venous patch was performed. Two dogs were lost a few hours after the correction operation. The remaining five dogs were followed for 12 months postoperatively. Renal perfusion was measured with a 133Xenon washout method just prior to the operation, 1 h, 6 and 12 months postoperatively. The glomerular filtration rate was measured using the 51Cr-EDTA method 1 wk before the operation, 3 wk, 2, 6, and 12 months after it. Six healthy adult dogs were used as controls for glomerular filtration rate measurements. Peripheral renin activity was measured at operation, just before the correction of aortic coarctation, 1/2, 1 h, 1, 3, 7 days, 2 and 6 months after the correction operation. Renal perfusion decreased significantly (p less than 0.05) immediately after the correction operation and rose again during the follow-up. Peripheral renin activity rose significantly (p less than 0.01) from the preoperative values and was at its greatest 1 day after the operation. Later on, peripheral renin activity values returned to normal. Coarctated dogs had significantly (p less than 0.01) lower glomerular filtration rate values than controls in each measurement except at the 2 months postoperative measurement. These results support decreased renal perfusion with resultant increased peripheral renin activity as part of the pathomechanism of the paradoxical hypertension observed after correction of coarctation.