Integrated instrumentation for ventricular pressure-volume relationship analysis

摘要

A PC based instrument has been developed for the study of the left ventricular pressure-volume relationship, based on the time-variable elastance theory. A multielectrode impedance catheter has been used to assess continuous on-line left ventricle volume. The acquisition system is composed of a 486-PC equipped with a National Instruments board, that supplies up to 16 analog input channels, and a Leycom Sigma-5 signal conditioner processor, that evaluates 5 segmental volumes and the total ventricular volume. ECG, ECG synchronism, five segmental volumes, total volume, left ventricle and aortic pressures are acquired and on-line displayed together with the P-V loop. Real time processing provides a continuous check of the loops shape related to the catheter position. An user friendly interface drives the operator by an ad-hoc menu and windows. The managing program has been developed in LabView software environment to guarantee the necessary robustness and safety of instrumentation to be used for cath-lab. The totality of the acquired signals is stored for subsequent retrieval and analysis; an off-line processing supplies the evaluation of the parallel volume, the end systolic pressure-volume relationship, the end diastolic pressure volume relationship, the useful ventricular work, the mechanical efficiency, and other standard parameters. The developed system has been accurately tested and calibrated by laboratory in-vitro measurements and subsequently used in more than 50 studies on patients. The study protocol consists of a basal acquisition, followed by the evaluation of the parallel conductance, necessary for the absolute left ventricle volume measurement. The transitory obstruction of the inferior venae Cavae by means of an inflated large size balloon is used to modify the cardiac preload in order to assess the end systolic and diastolic elastance. The on-line analysis capability and the parameters availability during the study allow the instrument to be used to assess drug infusions or long term hemodynamic monitoring in coronary care unit.