Mechanical restitution and post extrasystolic potentiation of perfused rat heart: Quantitative comparison of normal right and left ventricular responses

Nasrin Mesaeli, J. S. Juggi

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Interval-force relationship of right and left ventricles of the isolated perfused rat heart was quantified by fitting polynomial, linear and mixed linear-exponential functions to the mechanical restitution (MRC) and post extrasystolic potentiation (PESPC) curves. Ventricular maximum developed pressure (Pmax) and its first derivative (dP/dtmax) were used as indices of contractility. MRCs and PESPCs could be separated into two distinct phases: phase A and phase B of MRCs; phase I and phase II of PESPCs. These phases for the right and left ventricle of the rat heart could be explained on the same model of cellular kinetics of the activator calcium, but showed distinct differences from other species. Right and left ventricle inotropic reserve (CRmax), as quantified from the centre of mass of the phase B of MRCs (from normalized Pmax), was (mean ± SE): 132.4±2.05% and 132.1±1.7% at 1 Hz, which increased significantly (P<0.001) to 181.0±5.8% and 182.3±5.2% at 3.3 Hz, respectively. Linear regression of normalized right ventricle extrasystolic responses on the left ventricle responses gave a high correlation coefficient (typically r2=0.97). Time constants of the fitted mechanical restitution (T(MRC)) and post extraystolic potentiation (T(PESPC)) curves were nearly identical for both the ventricles atthe same priming frequency. Typically at 1 Hz, T(MRC) and T(PESPC) (from normalized dP/dtmax) were (mean±SE): 161.6±10.8 and 159.0±13.2 ms for right ventricle, and 196.1±14.5 and 188.3±10.7 ms for left ventricle, respectively. The results of this study indicate that interval-force relationship of the rat heart, as exemplified by CRmax and time constants of the fitted curves, could provide a usefull index for quantifying and comparing right and left ventricular functions.

Original languageEnglish
Pages (from-to)164-172
Number of pages9
JournalCanadian Journal of Cardiology
Issue number2
Publication statusPublished - 1992
Externally publishedYes


ASJC Scopus subject areas

  • Cardiology and Cardiovascular Medicine

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