Functional properties of a prototype rheolytic catheter for percutaneous thrombectomy. In vitro investigations

The performance of a rheolytic catheter designed to provide rapid fragmentation and evacuation of debris was evaluated. Specifically, fragmentation and evacuation efficiency was investigated in vitro.

Fragmentation, aspiration, and recanalization of large thrombotic occlusions (8-cm length, 6-mm inner diameter) composed of clot (n = 11) or collagen gels (n = 20) of different stiffness were performed with different jet pressures at rates optimized by visual observation and were recorded on videotape for subsequent analysis. The size and number of the resulting particles in the evacuated fluid and those remaining in the artificial vessel were determined using filtration and laser light scattering techniques. The rate of fragmentation, mean particulate size, and efficiency of evacuation were evaluated as a function of operating parameters and "clot stiffness."

Complete fragmentation of fresh thrombus occurred at 11,000 psi by direct action of the 6 radially disposed jets, which created a trapping vortex from which most of the particles (80%) were evacuated by suction. At lower pressure (5,500 psi), fragmentation efficiency was unchanged for fresh thrombus and softer 5% gels. Ninety-five percent of the thrombus was fragmented in very small particles with a mean diameter of 0.8 +/- 0.4 micron, while 5% of the mass of the fragmented thrombus was in particles > 40 microns. At 11,000 psi, the maximal rate of advancement associated with complete material fragmentation decreased with stiffness. For very stiff gels or heavily cross-linked old thrombus, complete fragmentation and removal of material was not achieved.

The high-pressure rheolytic catheter rapidly fragmented and evacuated large thrombi much larger than the catheter diameter--features with potential for treating large thrombi, such as acute pulmonary emboli or deep vein thrombi. However, this rapid forceful disruption may damage vessel walls and invariably creates a broad range of particulate sizes, which makes evacuation of almost all of the particulate material imperative to minimize clinically relevant distal embolization.