Evaluation of long-term variance of left ventricular performance indexes in closed-chest dogs

To assess the long-term variance of several parameters of left ventricular performance, we evaluated maximum rate of pressure development (dP/dtmax), ejection fraction, mean velocity of circumferential fiber shortening (VCF), the slope and volume-axis intercept of the end-systolic pressure-volume (PES-VES) relation, the stroke-work end-diastolic volume (SW-EDV) relation, and the dP/dtmax-EDV relation in six chronically instrumented dogs. Each dog was studied five times over a period of 3 wk in the conscious autonomically intact state, after autonomic blockade, and after administration of anesthesia. For each index under each set of testing conditions, a coefficient of variation was determined, defined as (SD/mean) x 100, and expressed as a percent. In conscious autonomically intact dogs, a low day-to-day variance was present in dP/dtmax (6.4%), ejection fraction (6.8%), mean VCF (6.5%), and the slope and volume intercept of the SW-EDV relation (7.2 and 6.2%), whereas higher variance was seen in the slope and intercept of the PES-VES relation (18.1 and 36.1%). The highest variance was present in parameters of the dP/dtmax-EDV relation. Thus dP/dtmax, ejection fraction, and the slope and volume intercept of the SW-EDV relation may be the most reliable indexes for long-term evaluation of left ventricular performance.