ABSTRACT 80

AORTIC OCCLUSION IN CARDIAC SURGERY:  CRITICAL ELEMENT ANALYSIS OF CLAMP INSERT DESIGN FOR IMPROVED SAFETY AND PERFORMANCE

Jerome B. Riebman, MD, John E. Orlando, Phillip Pesta, and Thomas J. Fogarty, MD
Santa Clara Valley Medical Center, San Jose, CA USA and Stanford University Medical Center, Stanford, CA USA

Purpose.  Temporary aortic occlusion for cardiac procedures is most commonly accomplished by external clamping.  Injury caused by clamps can be significant, including immediate problems like intimal tears / flaps, mural dissections and arterial rupture, or may lead to sequella such as thrombosis, embolism, intimal hyperplasia, or aneurysm formation.  Current clamp technology forces the vessel to change geometry and conform to the clamp to achieve occlusion.  Atherosclerotic vessels (with rigid plaques and calcification) are particularly susceptible to clamp injury due to their mural fragility and resistance to deformation.  While padded inserts are thought to lessen the impact, the elements of conformability, applied force and traction must be optimized for maximum safety and performance.

Methods.  After analyzing these critical mechanical elements, a novel clamp insert system was designed to provide improved performance.  Design engineering, mechanical and materials analysis lead to a clamp insert with the optimal design points.  The new insert design provides a high degree of conformability to irregularities in the vessel wall, maximizes the dispersion of the applied force, and maintains the required vascular traction.

Results.  Performance of the new design was evaluated in comparison to other commercially available clamps with padded inserts.  Conformability of the insert was determined by measuring the point-force resistance to generating a standard change in conformation.  The new insert design demonstrated a 46% improvement in conformability over the comparison group (mean 3.6 lbs. vs. 6.6, range 0.8-11).  Traction of the clamps with inserts was quantified by recording the movement of the clamp applied to a tissue model when a calibrated distracting force was applied.  The new insert design had a 110% improvement in traction versus the comparison clamps (mean 2.26 lbs. vs. 1.09, range 0.39-1.74).

Conclusion.  For surgical procedures requiring aortic occlusion, this innovative clamp insert is an improved device for vascular occlusion clamps in comparison to current external clamping technologies, demonstrating superior conformability and vascular traction.