Assessment of computer-controlled inflation/deflation for determining the properties of PTCA balloon catheters with pressure-volume curves

Restenosis is a significant problem after percutaneous transluminal coronar y angioplasty (PTCA), leading to further angina or even death. The mechanis ms causing restenosis are not well understood and the effect of the angiopl asty balloon on the artery wall is generally unknown. The aim of the resear ch presented here was to assess the repeatability with which measurements o f balloon pressure-volume characteristics could be made, to ensure that dif ferent balloons could be distinguished easily, an essential first step befo re the arteries themselves could be characterized. An inflation/deflation device was inflated with and without an attached bal loon under computer control at a constant speed to 8 bar. The accuracy and repeatability of the technique was assessed within a single measurement ses sion and between measurement sessions on six separate days. For each measur ement session, four repeated inflations/deflations were carried out and the average was determined. Compliance (volume change/pressure change), inflat ion volume and pressure drop at 8 bar were determined for various balloon c atheters of different size, type and manufacturer. The system repeatability SD for measuring volume without a balloon was +/-0 .0005 ml within a single measurement session, and +/-0.002 ml between indep endent days. With an attached balloon the repeatability SD for measuring vo lume was +/-0.001 ml within, and +/-0.003 ml between days. Compliance was d etermined with a repeatability SD of +/-0.16 mul bar(-1) within, and +/-0.9 4 mul bar(-1) between days. The inflation/deflation device and technique employed allowed small changes in volume and compliance to be differentiated. The system also enabled dif ferences due to the material characteristics for different PTCA balloons to be determined. Measured balloon characteristics were similar to the data g iven by manufacturers. This gives confidence in development of the techniqu e for clinical use.