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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 and PTCA catheters are described. Seventy-eight Palmaz-Schatz coronary stent delivery systems (PS-SDS), 8 Cook Flex-stents, 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 to 18-20 atm and PTCA catheters to 15 atm. Extraction and insertion times were measured in the last 10 PS-SDS and PTCA procedures. Mechanical analysis of JEX was performed for PS-SDS and a representative OTW PTCA catheter by solving the Navier Stokes equation for annular flow with changing geometry. The force/mass relationship, extraction time, average velocity, net force on the guidewire, and drag force on the guidewire were determined for varying pressures, catheter masses, and extraction wire lumen fluids. JEX was successful in 75/78 (96%) of coronary stents and in 243/247 (98%) of the PTCA catheter exchanges. After catheter removal, reinsertion of another OTW catheter was successful in 324/325 (99%) attempts. The mean force on the guidewire at 15 and 20 atm ranged from 16,000 to 22,000 dynes. Extraction velocity was approximately equal to 250% greater when saline was used compared to the more viscous 50/50 contrast-saline solution. Timed JEX extractions for the PS-SDS and 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 effective means of rapidly exchanging OTW stent delivery and PTCA catheters without using exchange wires, extension, or wire trapping devices. Analysis 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.