Standardization of end-systolic pressure-volume relation in the dog

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Abstract
Left ventricular (LV) volume elastance (Emax) and its volume intercept (Vo) are subject to considerable intersubject and interspecies variation. In humans, indexing with body surface area does not decrease variance. Because these are volume indexes, it was considered they would better standardize against body or LV weight. Fifteen open-chest mongrel dogs (mean wt 25.9 +/- 8.0 kg, range 15.6-42.5) were studied under 1% halothane anesthesia. Emax, derived by caval occlusion, averaged 9.0 +/- 4.4 mmHg X ml-1 (range 4.1-16.1) with a coefficient of variation (CV) of 48%. Average Vo was 19.6 +/- 10.5 ml (range 8.3-40.3) with a CV of 53%. LV weight was 110 +/- 21 g (range 78-147). Vo correlated best with LV weight: Y = 0.47 X - 31.78, r = 0.93, and adjustment of Vo by regression reduced CV to 20%. Emax was closely correlated with either 1/dog wt [Y = 313.02 (1/X) - 4.16, r = 0.88, CV = 23% after adjustment by regression] or 1/LV wt [Y = 2088.63 (1/X) - 10.72, r = 0.86, CV = 25% after adjustment]. Indexing of Emax by dog weight (CV = 29%) or LV weight (CV = 35%) reduced variation but by less than adjustment by regression. A subset of eight dogs had inotropic state varied, which had no effect on the relation between Vo and LV weight, but which resulted in an appropriate change (P less than 0.025) in the relation between Emax and 1/LV wt.(ABSTRACT TRUNCATED AT 250 WORDS)