Logistic Time Constant of Isovolumic Relaxation Pressure–Time Curve in the Canine Left Ventricle

Abstract

We conclude that the logistic model better fits LV isovolumic relaxation P(t) than the monoexponential model in the present heart preparation. We therefore propose TL as a better alternative to TE for evaluating LV lusitropism.

Superior Logistic Model for Decay of Ca2+ Transient and Isometric Relaxation Force Curve in Rabbit and Mouse Papillary Muscles

“…Such superiority of logistic fitting for the [Ca 2+ ] i decline over the conventional monoexponential function has not been reported previously, whereas the superiority of logistic fitting for the relaxation force curve has been found in previous studies. [18][19][20][21][22][23][24][25] Therefore, logistic fitting enables Caτ L and Fτ L to be obtained as more reliable indices for decay of the Ca 2+ transient and myocardial lusitropism. Calcium handling and relaxation: [Ca 2+ ] i is a central factor in excitation-contraction (E-C) coupling.…”

“…Despite the widespread use of monoexponential functions, the relaxation pressure curves may not be precisely characterized by this function as shown in semilogarithmic plots of pressure versus time 16) and the first time-derivative of pressure (dP/dt) versus time. 17) Furthermore, a logistic function has been proven to fit the isovolumic relaxation LV pressure curve in the excised canine heart more accurately, compared to the conventional monoexponential function, 18) and a logistic relaxation pressure time constant (Pτ L ) has been proposed and found to be a better ventricular lusitropic index than the Pτ E . 18,19) Moreover, the logistic function provides a better fit to the isometric relaxation force curve in the ferret right ventricular (RV) papillary muscle, compared to a monoexponential function, 20) and the logistic relaxation force time constant (Fτ L ) has been proposed as a better myocardial lusitropic index than the monoexponential relaxation force time constant (Fτ E ).…”

“…17) Furthermore, a logistic function has been proven to fit the isovolumic relaxation LV pressure curve in the excised canine heart more accurately, compared to the conventional monoexponential function, 18) and a logistic relaxation pressure time constant (Pτ L ) has been proposed and found to be a better ventricular lusitropic index than the Pτ E . 18,19) Moreover, the logistic function provides a better fit to the isometric relaxation force curve in the ferret right ventricular (RV) papillary muscle, compared to a monoexponential function, 20) and the logistic relaxation force time constant (Fτ L ) has been proposed as a better myocardial lusitropic index than the monoexponential relaxation force time constant (Fτ E ). 20) Furthermore, logistic fitting has been used in both animal experiments, such as for the rabbit RV papillary muscle 21) and trabeculae, 21) and calf, 22) rat 23) and ferret hearts, 24) and clinical settings.…”

“…16,17,27) However, it is evident that there is a considerable gap between the best-fit monoexponential curve and the actual relaxation curve near dP/dt min . 18) Similarly, the maximum rate of decline (ie, the minimum time-derivative of force (dF/dt min )) has been used as the onset of relaxation, 28) however, other starting points for relaxation have ] i decline have been used. 6) Therefore, the best starting point for the [Ca 2+ ] i decline and relaxation force curve remains unclear, and whether and how the onset of relaxation affects both logistic and monoexponential fitting remain to be elucidated.…”

Stunning and Right Ventricular Dysfunction Is Induced by Coronary Balloon Occlusion and Rapid Pacing in Humans: Insights From Right Ventricular Conductance Catheter Studies

“…Effective arterial elastance (Ea) to assess afterload was also assessed. The diastolic parameters of ventricular function were end‐diastolic pressure (EDP), the maximum rate of isovolumic relaxation (dP/dt min ), and the time constant of diastolic relaxation (Tau) 22, 23, 24. Tau represents the exponential decay of the RV pressure during isovolumic relaxation.…”