CORONARY STENT AND OVER-THE-WIRE CATHETER EXCHANGE USING STANDARD LENGTH GUIDEWIRES - JET EXCHANGE (JEX) PRACTICE AND THEORY

The practice and theoretical principles of hydraulic exchange of over- the-wire (OTW) stent end PTCA catheters are described. Seventy-eight P almaz-Schatz coronary stent delivery systems (PS-SDS), 8 Cook Flex-ste nts, and 247 assorted OTW catheters were delivered and extracted over standard length coronary guidewires using Jet Exchange (JEX). JEX was performed by pressurizing the wire lumen of coronary stent catheters t o 18-20 atm and PTCA catheters to 15 atm. Extraction and insertion tim es were measured in the last 10 PS-SDS and PTCA procedures. Mechanical analysis of JEX was performed for PS-SDS and a representative OTW PTC A catheter by solving the Navier Stokes equation for annular flow with changing geometry. The force/mass relationship, extraction time, aver age velocity, net force on the guidewire, and drag force on the guidew ire were determined for varying pressures, catheter masses, and extrac tion wire lumen fluids. JEX was successful in 75/78 (96%) of coronary stents and in 243/247 (98%) of the PTCA catheter exchanges. After cath eter removal, reinsertion of another OTW catheter was successful in 32 4/325 (99%) attempts. The mean force on the guidewire at 15 and 20 atm ranged from 16,000 to 22,000 dynes. Extraction velocity was approxima te to 250% greater when saline was used compared to the more Viscous 5 0/50 contrast-saline solution. Timed JEX extractions for the PS-SDS an d standard PTCA catheters were 8.9 +/- 2.3 sec and 5.3 +/- 1.4 sec and compared favorably to theoretical calculations of extraction times, 9 .8 and 3.8 sec respectively. JEX is a simple, reliable, and cost effec tive means of rapidly exchanging OTW stent delivery and PTCA catheters without using exchange wires, extension, or wire trapping devices. An alysis of the principles of conservation of momentum provides a basis for understanding the physical laws that permit safe and expedient JEX in a clinically setting. (C) 1997 Wiley-Liss, Inc.