Balloon embolectomy catheters in small arteries. IV. Correlation of shear forces with histologic injury.

Experiments were performed in 18 dogs to evaluate the character and time course of arterial injury caused by balloon embolectomy catheters. Injury was correlated with balloon-artery shear forces. Shear forces were regulated intraoperatively. Thirty gram force caused no injury in 14 specimens. Sixty gram force stripped the intimal endothelium in two of four specimens examined at 2 days. Repair consisted of myointimal hypercellularity with return to normal one-cell thickness within 28 days. Ninety and 120 gram force stripped the intimal endothelium in 32 specimens with no medial injury. Repair again consisted of myointimal proliferation, which returned to normal in most vessels at 28 days. All vessels appeared normal at 6 months. This indicates that balloon embolectomy catheters can be a safe operative tool provided excessive shear forces are not imposed. This is quite feasible, for usual embolectomies were found to require about 60 gm shear force. Two hundred gram initial force caused intimal injury and fracturing of the internal elastic lamina, with the latter injury persisting even after 6 months.