New mechanoenergetic evaluation of left ventricular contractility in in situ rat hearts

Abstract

We recorded a series of ejecting left ventricular (LV) pressure (P)-volume (V) loops of in situ rat hearts during a gradual ascending aortic occlusion. The end-systolic (ES) P-V relationship (ESPVR) was upward convex curvilinear regardless of LV contractility. The ESPVR was shifted upward in an enhanced contractility by dobutamine and downward in a depressed contractility by propranolol; ESP at a midrange V of 0.1 ml/g LV on each ESPVR increased from 131 +/- 11 to 192 +/- 17 mmHg and decreased from 136 +/- 10 to 110 +/- 7 mmHg, respectively. Furthermore, we obtained an upward concave curvilinear pressure-volume area (PVA; a measure of total mechanical energy)-V (preload) relationship to assess LV work capability in each contractility. This relationship also shifted upward in enhanced contractility and downward in depressed contractility; the PVA at midrange V increased from 7.9 +/- 1.2 to 12.3 +/- 1.5 mmHg. ml.beat-1.g-1 and decreased from 8.2 +/- 0.9 to 6.4 +/- 0.8 mmHg.ml.beat-1.g-1. We conclude that the heights of the ESPVR and PVA-V relationship curves can evaluate LV contractility mechanoenergetically.

New Index for Oxygen Cost of Contractility from Curved End-Systolic Pressure-Volume Relations in Cross-Circulated Rat Hearts.

“…We determined PVA by the method described below because the ESPVR of the rat LV was an upward convex curve [1][2][3][4][5][6]. We fitted the end-systolic and end-diastolic P-V points by the following equations:…”

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Recently, we have consistently observed curved endsystolic pressure-volume relations (ESPVRs) of the left ventricle (LV) in rat blood-perfused [1][2][3] and crystalloid-perfused whole heart preparations [4] and in situ ejecting rat hearts [5,6], like those of the puppy LV [7] and adult canine LV in supernormal contractility [8,9]. These studies suggest more generality of the curvilinear than linear ESPVR in different animal species.

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Force-length relations in isolated intact cardiomyocytes subjected to dynamic changes in mechanical load

“…It has been reported previously that larger mammals (e.g., rabbit and dog) show a linear end-systolic pressurevolume relation (ESPVR) (10,28), whereas smaller rodents (e.g., mouse or rat) have convex ESPVR (9,32). The relation between the intrinsically three-dimensional (3D) processes that underlie ESPVR characteristics and the one-dimensional nature of ESFLR is nontrivial.…”

Ventricular remodeling and diastolic myocardial dysfunction in rats submitted to protein-calorie malnutrition

“…Parameters assessed to evaluate systolic function are those most commonly utilized in this preparation (6,21,38,43,46): 1) slope of end-systolic pressure-volume normalized relationship (ESPVNR; mmHg ⅐ ml Ϫ1 ⅐ g Ϫ1 ) [volume was normalized to LVW as suggested by Suga et al (44) and the mean ESPVNR curve was obtained; steeper slope indicates increased myocardial contractility]; 2) maximum rate of ventricular pressure rise (ϩdP/dt; mmHg/s); and 3) maximum developed pressure (DP max; mmHg), corresponding to the difference between peak systolic pressure and diastolic pressure with the LV balloon filled to develop an end-diastolic pressure of 25 mmHg.…”