Computer software for the on-line measurement of the left ventricular end-systolic pressure-dimension relationship

A microcomputer system was designed to measure the end-systolic pressure-dimension relationship (ESPDR), an index of cardiac contractility that is independent of preload, afterload, and heart rate. To test the system, pressure-dimension data were obtained from swine left ventricles and from a mathematical model of the heart. Algorithms for filtering, location of end-systole, selection of the measurement interval, and calculation of the ESPDR were evaluated on the basis of speed, precision, accuracy, and robustness. The resulting program runs on an IBM-AT and measures ESPDR on-line within 60 seconds of the start of data acquisition. By reducing the time spent in data analysis and providing rapid feedback of information, the on-line software has increased productivity and facilitated improvements in experimental technique.