[Evaluation of cardiac and myocardial inotropism and lusitropism using half-logistic curve-fitting].
Half-logistic (h-L) function, which is half of the sigmoidal, logistic function with a boundary at the inflection point, curve-fits the isovolumic relaxation left ventricular (LV) pressure curve from the minimum of the first order time derivative of pressure (dP/dt(min)), and the myocardial isometric relaxation tension curve from the minimum of the first order time derivative of tension (dF/dt(min)) superior to the conventional mono-exponential function. Recently, we found that h-L function could curve-fit the other partial curves. The isovolumic LV pressure curve in the excised, cross-circulated canine heart, was divided into four distinct phases with boundaries set at the maximum of dP/dt (dP/dt(max)), peak LV pressure, dP/dt(min), and LV end-diastolic pressure (LVEDP) resulting in the first phase from the point corresponding to QR on the electrocardiogram to dP/dt(max); the second phase from dP/dt(max) to the peak LV pressure; the third phase from the peak LV pressure to dP/dt(min); and the fourth phase from dP/dt(min) to LVEDP. Similarly, the isometric twitch tension curves in the mouse LV and rabbit right ventricular (RV) papillary muscles were divided into four distinct phases with boundaries set at the maximum of dF/dt (dF/dt(max)), peak tension, dF/dt(min), and resting tension resulting in the first phase from the point corresponding to twitch stimulation to dF/dt(max); the second phase from dF/dt(max) to the peak tension; the third phase from the peak tension to dF/dt(min); and the fourth phase from dF/dt(min) to resting tension. The h-L correlation coefficient (r) values for the sequential curves were larger than the m-E r values, respectively, and the h-L residual mean squares (RMS) were smaller than the m-E RMS values, respectively. The h-L time constants are indices which quantify cardiac and myocardial inotropism and lusitropism more accurately. We consider that the h-L approach also applies for evaluation of the isovolumic contraction phase and the isovolumic relaxation phase in the beating hearts.
Mizuno
Ju
J
Department of Anesthesiology, Teikyo University School of Medicine, Tokyo 173-8605.
Morita
Shigeho
S
Otsuji
Mikiya
M
Hanaoka
Kazuo
K
Kurihara
Satoshi
S
D000818:Animals; D004285:Dogs; D006334:Heart Function Tests / Q000379:methods*; D006801:Humans; D066298:In Vitro Techniques; D016015:Logistic Models; D051379:Mice; D009200:Myocardial Contraction; D011817:Rabbits