Circulation Research, Vol 66, 218-233, Copyright © 1990 by American Heart Association

ARTICLES

Late-systolic pumping properties of the left ventricle. Deviation from elastance-resistance behavior

KB Campbell, RD Kirkpatrick, GG Knowlen and JA Ringo
Department of Veterinary and Comparative Anatomy, Physiology, and Pharmacology, Washington State University, Pullman 99164-6520.

Elastance-resistance [E(t)-R] representations of the left ventricle (LV) were evaluated for their ability to reproduce instantaneous pressure [P(t)] and outflow [Q(t)]. Experiments were performed in open- chest rats. P(t) and Q(t) were measured during steady-state ejecting beats and during a beat in which the aorta was suddenly clamped. The degree of clamping varied from partial to total occlusion. The total occlusion beat was considered an isovolumic beat that generated an isovolumic pressure [Piso(t)] with a characteristic time to maximal Piso(t) [Tpisomax]. In ejecting beats, 34% of stroke volume was delivered after Tpisomax. P(t) and Q(t) from the steady-state ejecting beats and Piso(t) from the clamped beat were then used to estimate parameters of an E(t)-R model. Components of P(t) and Q(t) not accounted for by E(t)-R were identified and termed extra-pressure [Pext(t)] and extra-outflow [Qext(t)]. Pext(t) and Qext(t) were near- zero valued until Tpisomax; then they became systematically positive and finally negative valued after end ejection. During partial aortic occlusion, P(t) was elevated and Q(t) was reduced. However, the time of ejection was extended, and the fraction of stroke volume delivered after Tpisomax increased as P(t) was made higher. Partial occlusion also prolonged the positive phase of Pext(t) and Qext(t). Elements possessing "active" and "deactive" properties were added to the E(t)-R model in an attempt to account for Pext(t) and Qext(t) during partial occlusion. Optional forms of these elements were considered. These expanded E(t)-R models were fitted to basal ejecting data and then asked to predict data from a partial occlusion beat. All expanded models failed to adequately predict the partial occlusion pressure and/or outflow. It was concluded that 1) late ejection was quantitatively important to LV pumping, 2) behavior during late ejection was inconsistent with E(t)-R, and 3) ad hoc modification of E(t)-R models was not likely to yield LV pumping models that could satisfactorily reproduce instantaneous P(t) and Q(t) behavior over the entire ejection period.

This article has been cited by other articles:

				K. B. Campbell, A. M. Simpson, S. G. Campbell, H. L. Granzier, and B. K. Slinker Dynamic left ventricular elastance: a model for integrating cardiac muscle contraction into ventricular pressure-volume relationships J Appl Physiol, April 1, 2008; 104(4): 958 - 975. [Abstract] [Full Text] [PDF]

				D.-F. Yeih, L.-Y. Lin, H.-I Yeh, Y.-J. Lai, F.-T. Chiang, C.-D. Tseng, S.-H. Chu, and Y.-Z. Tseng Temporal changes in cardiac force- and flow-generation capacity, loading conditions, and mechanical efficiency in streptozotocin-induced diabetic rats Am J Physiol Heart Circ Physiol, February 1, 2008; 294(2): H867 - H874. [Abstract] [Full Text] [PDF]

				D. Burkhoff, I. Mirsky, and H. Suga Assessment of systolic and diastolic ventricular properties via pressure-volume analysis: a guide for clinical, translational, and basic researchers Am J Physiol Heart Circ Physiol, August 1, 2005; 289(2): H501 - H512. [Abstract] [Full Text] [PDF]

				K. B. Campbell, Y. Wu, A. M. Simpson, R. D. Kirkpatrick, S. G. Shroff, H. L. Granzier, and B. K. Slinker Dynamic myocardial contractile parameters from left ventricular pressure-volume measurements Am J Physiol Heart Circ Physiol, July 1, 2005; 289(1): H114 - H130. [Abstract] [Full Text] [PDF]

				K.-C. Chang, H.-M. Lo, and Y.-Z. Tseng Systolic Elastance and Resistance in the Regulation of Cardiac Pumping Function in Early Streptozotocin-Diabetic Rats Experimental Biology and Medicine, April 1, 2002; 227(4): 251 - 259. [Abstract] [Full Text] [PDF]

				K.-C. Chang, Y.-I Peng, F.-C. Lee, and Y.-Z. Tseng Effects of Food Restriction on Systolic Mechanical Behavior of the Ventricular Pump in Middle-aged and Senescent Rats J. Gerontol. A Biol. Sci. Med. Sci., March 1, 2001; 56(3): 108B - 115. [Abstract] [Full Text]

				K.-C. Chang, Y.-I Peng, S.-H. Dai, and Y.-Z. Tseng Age-Related Changes in Pumping Mechanical Behavior of Rat Ventricle in Terms of Systolic Elastance and Resistance J. Gerontol. A Biol. Sci. Med. Sci., September 1, 2000; 55(9): 440B - 447. [Abstract] [Full Text]