Balloon embolectomy catheters in small arteries. III. Surgical significance of eccentric balloons.

Some embolectomy balloons distend eccentrically. This study was undertaken to compare balloon eccentricity in air with that which occurs in arteries, to determine the influence of balloon eccentricity on shear force, and to estimate the injury potential of eccentric balloons. We studied 21 Edwards and 17 Shiley catheters in 24 dog carotid arteries in vitro. Each vessel was mounted horizontally in a Krebs-Ringer bath with one end of the vessel suspended from a force gauge. Catheters were inserted through an arteriotomy, and balloons were distended to lateral wall pressures of 25, 75, and 125 mm Hg. X-ray studies were used to measure balloon eccentricity--that is, the ratio of larger radius (R) to smaller radius (r). Comparison revealed a high correlation (r = 0.88, P less than 0.05) between R/r values in air and R/r values within arteries. Shear forces were produced when balloons were withdrawn through arteries. Regression equations revealed that the shear force increased about 10% for each unit increase in R/r. However, extremely eccentric balloons (R/r 8:1) pushed the catheter shaft deep into the vessel wall, gouging a linear tear in the media. This was seen in vitro and in two dogs studied 2 and 14 days after embolectomy. We conclude that balloon eccentricity in air is an accurate indicator of balloon eccentricity within arteries, that moderately eccentric balloons (R/r 3:1) are acceptable for clinical use, but that extremely eccentric balloons (R/r greater than 3:1) may cause severe injury and should not be used in the operating room.