Balloon embolectomy catheters in small arteries. I. Lateral wall pressures and shear forces

Balloon embolectomy catheters were studied in 2 to 3 mm canine arteries in vitro to evaluate the determinants of lateral wall pressure (LWP), balloon-artery shear force, and shear stress. LWP was determined by examination of the pressure-diameter curve of each artery and identification of the diameter at each level of infected volume. The following results were obtained: (1) LWP was determined by balloon diameter and was poorly related to balloon pressure. (2) When balloons were filled to clinical criteria, mean LWPs of 50 to 10 mm Hg for 24 Shiley catheters and 62 +/- 11 mm Hg for 24 Edwards catheters were recorded. (3) Shear forces increased directly with LWP. (4) In most cases, shear forces at any LWP were not significantly different for Edwards and Shiley catheters. (5) Shear forces had a high initial component and a lower dynamic component; the latter component was decreased slightly by increasing withdrawal velocity. (6) Shear forces were lower (P less than 0.05) with small catheters than with larger catheters, i.e., 3F less than 4F less than 5F. (7) Shear stresses were at least 84 times greater than the critical stress for the intima. These data suggest the following clinical guidelines: (1) Every effort should be made to achieve the low LWP since this strongly influences shear force. (2) The smallest effective catheter should be used. (3) Negligible benefit may be gained if catheters are withdrawn at moderate velocities.