Cardiodynamic conditions for the linearity of preload recruitable stroke work

Abstract

Studies reported in the literature show that the stroke work (SW) versus end-diastolic volume (Ved) relationship, namely, the preload recruitable stroke work relation (PRSW), is experimentally linear in closed-chest dog hearts and its slope reflects left ventricular contractility. We considered the theoretical cardiodynamic conditions necessary for the linearity of the SW-Ved relation by utilizing ventricular end-systolic elastance, Emax (ventricular contractility), and effective arterial elastance, Ea (arterial afterload). We simulated the SW-Ved relation, using four theoretical models of the left ventricle, as follows: Ea is constant and the end-systolic pressure-volume relation (ESPVR) is linear (model 1), or nonlinear (model 2), and Ea is variable and ESPVR is linear (model 3), or nonlinear (model 4). The results show that the SW-Ved relation can be linear in both linear and nonlinear ESPVR models (models 3 and 4) only when Ea is variable. In these models, end-systolic pressure (Pes) and Ea should gradually fall, maintaining the stroke volume (SV) relatively constant with decreases in Ved until the low end of the physiological Ved range. Then, Ea should rise sharply so that Pes does not fall below the critical level. These results suggest that the autoregulation mechanisms of an intact animal operate to adapt the arterial afterload against acute changes in LV preload, maintaining cardiac output and coronary artery pressure. Such mechanisms may thus produce a linear SW-Ved relation over a wide range of conditions.

β2-Microglobulin knockout mice treated with anti-asialoGM1 exhibit improved hemodynamics and cardiac contractile function during acute intra-abdominal sepsis

“…This approach also allows for determination of variables such as the ESPVR, left ventricular E max , and PRSW that are believed to be load-insensitive indicators of myocardial contractility (12,34,35). The intact animal model also allows measurement of cardiac function in the presence of circulating cytokines, autonomic nervous system contributions, and humeral factors during sepsis.…”

Endothelin-1 Receptor Antagonist Prevents Deterioration of Left Ventricular Function and Coronary Flow Reserve in Brain-Dead Canine Heart

“…26 In addition, the SW-V ed relation can be linear only when afterload falls gradually with V ed until the low end of the physiologic range (about 20 ml), and rises sharply with decreases in V ed in the non-physiologic low V ed range. 27 After brain death, V ed was lower than the physiologic range (Table 2) and afterload could not rise because of loss of sympathetic tone. 6,28 In the present study, neither E es nor dE/dt max , rather only M SW , was significantly decreased-even in the TAK group at 60 minutes after brain death.…”

Experimental validation of the prestretch-strain relationship as a non-invasive index of left ventricular myocardial contractility

“…Despite the remarkable progress in cardiovascular research, the accurate (non-invasive) quantification of left ventricular (LV) contractile function remains a major challenge in clinical practice. As such, many studies have focused on identifying the best possible index of LV contractility taking into account its load dependency, its sensitivity to inotropic and chronotropic state and its reproducibility [1][2][3][4][5][6][7][8][9][10][11].Currently, the slope (E max ) of the end systolic pressure volume relationship (ESPVR) and the preload recruitable stroke work (PRSW) are considered the gold standards measurements of LV contractility. Additionally, the slope of the dP/dt max -end diastolic volume (EDV) relationship is also commonly used as an estimate of LV contractility.…”

“…Additionally, the slope of the dP/dt max -end diastolic volume (EDV) relationship is also commonly used as an estimate of LV contractility. All these measurements are based on the Frank-Starling law of the heart that describes a direct relation between preload and the active force developed by the ventricle [1][2][3][4][5]8]. Available data from experimental studies on mammals and humans points towards PRSW as the most reliable index due to its load independency, its sensitivity to contractile changes and its low measurement variability [1,3,5,6,7,9].…”

“…All these measurements are based on the Frank-Starling law of the heart that describes a direct relation between preload and the active force developed by the ventricle [1][2][3][4][5]8]. Available data from experimental studies on mammals and humans points towards PRSW as the most reliable index due to its load independency, its sensitivity to contractile changes and its low measurement variability [1,3,5,6,7,9]. In contrast, the maximal slope of the dP/dt max -EDV relationship was reported to be load dependent and sensitive to measurement variability while data on E max is contradictory, with some studies reporting a degree of load dependency and non-linearity of the measurement under non-physiologic conditions while others do not [1][2][3][4][5][6][10][11][12][13][14][15].…”