Early myointimal hyperplasia after balloon catheter embolectomy: effect of shear forces and multiple withdrawals.

Arterial stenosis occurring after balloon catheter embolectomy may be caused by myointimal hyperplasia (MIH). This study investigated the effects of shear force and repeated catheter withdrawals on the development of MIH after embolectomy. The procedures were performed in the common carotid and common femoral arteries of 18 anesthetized dogs. During catheter withdrawal, the balloons were filled gradually to produce shear forces rising smoothly from 50 to 200 gm. Four weeks after embolectomy, the vessels were perfusion-fixed in situ with 2% glutaraldehyde and were excised. The thickness and circumferential extent of MIH were measured in cross sections from segments of the vessels exposed to shear forces of 50, 100, and 200 gm. Sixty-nine of 72 arteries remained patent. Low shear force (50 gm) consistently elicited less MIH than did higher shear forces (p less than 0.05). At each level of shear force, repeated withdrawals resulted in greater circumferential extent of MIH than did single withdrawals (p less than 0.005). Although clinically it usually is necessary to perform multiple passes during balloon embolectomy, these data suggest that, in humans, attempts should be made to perform a minimal number of catheter withdrawals at low shear force to minimize the subsequent development of MIH.