Heart disease is the leading cause of death in the western world, and percutaneous transluminal coronary angioplasty (PTCA) and stent deployment are standard procedures used to reopen and/or stabilize blocked coronary arteries. Despite considerable improvements in these techniques, restenosis is still a long term problem, with patients requiring repeated procedures. Hence, further investigation of the mechanisms that contribute to arterial wall remodelling may help to improve the success of percutaneous coronary interventions (PCI).
The aim of this study was to assess a measurement technique for its ability to determine the compliance of mock arteries using different balloon catheters during a standard angioplasty procedure. Pressure-volume (PV) curves were used to determine the combined mechanical response of the system, the balloon catheters and mock arteries in real time. The validity of subtracting the system compliance from the PV curves containing the system, balloon and/or mock artery was assessed using two-independent measurement techniques to determine the balloon inflation volume.
Eighteen balloon catheters from four different manufactures were inflated inside three mock arteries with differing compliances (high, medium, low) and the resulting PV curves were recorded. The compliances of the three mock arteries were then determined from the PV curves. The results were compared to reference values of the three mock arteries, which were determined from one of the independent mechanical tests. Corrections for each balloon catheter type and each individual balloon catheter were studied. A correlation coefficient of 0.99 between the two-independent volume measurement techniques confirmed the validity of subtracting the system compliance. The compliance values for the high, medium and low compliant mock arteries, obtained by using the different balloon catheters, varied between 4 and 12, 3 and 9 and, 2 and 5 (µl/bar) mm-1, respectively. Standard deviation varied from 0.1 up to 2.1 (µl/bar) mm-1. This was equivalent to a mean variation factor (root mean square/mean) of 29%, which reduced to 12% with correction. The system was always able to detect differences between mock arteries in spite of the large variation with different balloon catheters.
The study has shown that it is possible to determine compliances of different mock arteries using different balloon catheters. However, the determined compliances needed to be corrected for different mechanical properties of the balloons used.
Olbrich T, Murray A. Assessment of a technique to determine the mechanical properties of coronary arteries using mock arteries. Physiol Meas 2004; 25: 1-15.
Mr. Tom Olbrich, Freeman Unit, Newcastle upon Tyne. Tel: +44 (0)191-223-1370.
Regional Medical Physics Department, Newcastle General Hospital, Newcastle upon Tyne, NE4 6BE, UK.
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