M.S. Thesis Presentation by Nathan Earl Brewton
Tuesday, February 23, 1999

(Dr. David N. Ku, advisor)

"Intimal and Medial Alterations Following Balloon Catheter Intervention"

Abstract

Balloon catheter embolectomy is a surgical procedure for minimally invasive removal of occlusive emboli and thrombi. In this procedure, a catheter is first inserted into a vessel through an incision and forced past a vascular occlusion. Then a balloon at the distal tip of the catheter is inflated via syringe and withdrawn removing the occlusion. Though this procedure is the excepted means for removal of vascular occlusions, it is associated with some long-term complications. Intimal thickening and thrombosis are common clinical sequela believed to result from sub-acute injury to the intimal surface and medial tissue. Balloon catheter design represents a compromise between balloon efficacy and injurious properties of the balloon.

In this study, several means for quantification of balloon catheter efficacy and incurred damage were developed. Efficacy was determined by measuring the mass of synthetic clot removed from porcine carotid arteries. Intimal damage was assessed by staining catheterized intimal surfaces with MTT. MTT staining density was quantified by image analysis and used as an estimate of injury. Finally, a test stage was developed so that real-time catheter tension could be measured during balloon withdrawal from excised porcine carotid artery segments. These techniques were applied to a textured prototype balloon and the standard Fogarty balloon.

None of the synthetic clots used in this experiment were adherent to the arterial wall. However, the use of synthetic clot illustrated a particular design flaw of the prototype balloon. MTT staining proved to be an effective means for intimal damage quantification, showing significant differences in damage between the Fogarty balloon and the prototype. Based on catheter tension, estimates of balloon-artery dynamic friction coefficients during withdrawal were made. The friction coefficient on the first withdrawal for the prototype balloon was significantly higher than that for the Fogarty balloon.

These techniques established definitive differences between the prototype and Fogarty balloons. Ultimately, better insight into the nature of injury was gained and possible design improvements for the prototype balloon were realized.