ECG GATED PRESSURE VOLUME RELATIONSHIPS UTILIZING SCINTIGRAPHIC IMAGE DATA.

A computer-aided measurement and control (CAMAC)-based acquisition system is described which is capable of acquiring real-time ECG-gated nuclear scintigraphic cardiac images synchronized with simultaneous ECG-gated pressure-time relationships. The system can simultaneously acquire both real-time frame-mode and list mode data and up to seven pressures. Both gated and beat-by-beat pressures and volume data can be analyzed. Communication to the host computer controlling the CAMAC crate is via the IEEE-488 interface standard. Gamma camera data rates of up to 50,000 16-b events/s can be handled (over 100,000 events/s if real-time list mode is disabled) including writing list mode data to disk. Applications in the study of left ventricular (LV) function in the region of negative dP/dV for subjects with systemic hypertension are presented. LV pressure/scintigraphic images were acquired at rest, and at three pacing levels. This sequence was repeated for the hypertensives after administration of drugs (ergonovine, nitroprusside, and/or verapamil). The resulting time activity curves (TACs) were Fourier filtered (four to seven harmonic sharp cutoff) to create dP/dV relationships at each pacing level, as well as P-V loops. Thus systolic and diastolic contractility or compliance could be studied under a variety of load conditions. In the region of negative dP/dV immediately following opening of the mitral value, dP/dV was found to exhibit an approximately exponential behavior.