scholarly journals Temperature-dependent inotropic and lusitropic indices based on half-logistic time constants for four segmental phases in isovolumic left ventricular pressure–time curve in excised, cross-circulated canine heart

2017 ◽  
Vol 95 (2) ◽  
pp. 190-198 ◽  
Author(s):  
Ju Mizuno ◽  
Satoshi Mohri ◽  
Takeshi Yokoyama ◽  
Mikiya Otsuji ◽  
Hideko Arita ◽  
...  
Keyword(s):  
Least Squares Method ◽  
Left Ventricular Pressure ◽  
Left Ventricular ◽  
Canine Heart ◽  
Temperature Dependent ◽  
Time Curve ◽  
Time Constants ◽  
Pressure Time ◽  
Systolic And Diastolic Function ◽  
Increasing Temperature

Varying temperature affects cardiac systolic and diastolic function and the left ventricular (LV) pressure–time curve (PTC) waveform that includes information about LV inotropism and lusitropism. Our proposed half-logistic (h-L) time constants obtained by fitting using h-L functions for four segmental phases (Phases I–IV) in the isovolumic LV PTC are more useful indices for estimating LV inotropism and lusitropism during contraction and relaxation periods than the mono-exponential (m-E) time constants at normal temperature. In this study, we investigated whether the superiority of the goodness of h-L fits remained even at hypothermia and hyperthermia. Phases I–IV in the isovolumic LV PTCs in eight excised, cross-circulated canine hearts at 33, 36, and 38 °C were analyzed using h-L and m-E functions and the least-squares method. The h-L and m-E time constants for Phases I–IV significantly shortened with increasing temperature. Curve fitting using h-L functions was significantly better than that using m-E functions for Phases I–IV at all temperatures. Therefore, the superiority of the goodness of h-L fit vs. m-E fit remained at all temperatures. As LV inotropic and lusitropic indices, temperature-dependent h-L time constants could be more useful than m-E time constants for Phases I–IV.

scholarly journals Logistic Characterization of Left Ventricular Isovolumic Pressure-Time Curve.

1995 ◽  
Vol 45 (3) ◽  
pp. 535-552 ◽  
Author(s):  
Hiromi MATSUBARA ◽  
Junichi ARAKI ◽  
Miyako TAKAKI ◽  
Sachiko T. NAKAGAWA ◽  
Hiroyuki SUGA
Keyword(s):  
Left Ventricular ◽  
Time Curve ◽  
Pressure Time

Loading sequence is a major determinant of afterload-dependent relaxation in intact canine heart

1985 ◽  
Vol 249 (4) ◽  
pp. H747-H754 ◽  
Author(s):  
M. Hori ◽  
M. Inoue ◽  
M. Kitakaze ◽  
K. Tsujioka ◽  
Y. Ishida ◽  
...  
Keyword(s):  
Left Ventricular ◽  
Autonomic Nerve ◽  
Segment Length ◽  
Exponential Fitting ◽  
Canine Heart ◽  
Total Load ◽  
Time Constants ◽  
Fitting Method ◽  
Loading Sequence

To elucidate the role of loading sequence in afterload-dependent slowed relaxation in hearts in situ, the time constants (Texp from best exponential fitting method and TL from semilogarithmic method) of isovolumetric left ventricular (LV) pressure decay were studied in nine anesthetized open-chest dogs under the pharmacological blockade of autonomic nerve activity. An afterload change was imposed by clamping the ascending or descending aorta to make the peak LV pressure early or late in systole. During afterload interventions, in contractions with the peak LV pressure in late systole Texp and TL were significantly (P less than 0.05) larger than in those with the peak LV pressure in early systole in any comparable peak LV pressure range. Moreover, both time constants were directly correlated (P less than 0.01) with the time of peak LV pressure irrespective of peak LV pressure and clamp mode of aorta. In another protocol, marked differences both in Texp and TL were also observed between each of 25 pairs of contractions with different loading sequence but with comparable peak LV pressure and LV dimension (segment length). Thus afterload-dependent slowed relaxation in hearts in situ could not be attributed to an increased total load but to the altered loading sequence associated with an increase in afterload.

Half-logistic time constant: a more reliable lusitropic index than monoexponential time constant regardless of temperature in canine left ventricle

2008 ◽  
Vol 86 (3) ◽  
pp. 78-87 ◽  
Author(s):  
Ju Mizuno ◽  
Hiromi Matsubara ◽  
Satoshi Mohri ◽  
Juichiro Shimizu ◽  
Shunsuke Suzuki ◽  
...  
Keyword(s):  
Time Constant ◽  
Time Course ◽  
Least Squares Method ◽  
Diastolic Pressure ◽  
Time Derivative ◽  
Left Ventricular ◽  
Monoexponential Model ◽  
Increasing Temperature ◽  
T Tau ◽  
Pressure Fall

Temperature changes influence cardiac diastolic function. The monoexponential time constant (tauE), which is a conventional lusitropic index of the rate of left ventricular (LV) pressure fall, increases with cooling and decreases with warming. We have proposed that a half-logistic time constant (tauL) is a better lusitropic index than tauE at normothermia. In the present study, we investigated whether tauL can remain a superior measure as temperature varies. The isovolumic relaxation LV pressure curves from the minimum of the first time derivative of LV pressure (dP/dtmin) to the LV end-diastolic pressure were analyzed at 30, 33, 36, 38, and 40 °C in excised, cross-circulated canine hearts. tauL and tauE were evaluated by curve-fitting using the least squares method and applying the half-logistic equation, P(t) = PA/[1 + exp(t/tauL)] + PB, and the monoexponential equation, P(t) = P0exp(–t/tauE) + P∞. Both tauL and tauE increased significantly with decreasing temperature and decreased with increasing temperature. The half-logistic correlation coefficient (r) values were significantly higher than the monoexponential r values at the 5 above-mentioned temperatures. This implies that the superiority of the goodness of the half-logistic fit is not temperature dependent. The half-logistic model characterizes the amplitude and time course of LV pressure fall more reliably than the monoexponential model. Hence, we concluded that tauL is a more useful lusitropic index regardless of temperature.

O2cost of contractility but not of mechanical energy increases with temperature in canine left ventricle

1999 ◽  
Vol 277 (1) ◽  
pp. H65-H73 ◽  
Author(s):  
Takeshi Mikane ◽  
Junichi Araki ◽  
Shunsuke Suzuki ◽  
Ju Mizuno ◽  
Juichiro Shimizu ◽  
...  
Keyword(s):  
Mechanical Energy ◽  
Left Ventricular ◽  
Beating Heart ◽  
Canine Heart ◽  
Oxygen Cost ◽  
Temperature Dependent ◽  
Total Mechanical Energy ◽  
Myocardial Temperature ◽  
Linear Manner ◽  
Dependent Processes

We investigated the effects of myocardial temperature on left ventricular (LV) mechanoenergetics in the excised, cross-circulated canine heart. We used the framework of the LV contractility ( Emax)-pressure-volume area (PVA; a measure of total mechanical energy)-myocardial oxygen consumption (Vo2) relationship. We have shown this framework to be useful to integrative analysis of the mechanoenergetics of a beating heart. In isovolumic contractions at a constant pacing rate, increasing myocardial temperature from 30 to 40°C depressed Emaxand increased the oxygen cost of Emax, which was enhanced by dobutamine, in a linear manner. However, the slope of the Vo2-PVA relation (reciprocal of contractile efficiency) and its Vo2intercept remained constant. Q10values of Emax, the oxygen cost of Emax, and the oxygen cost of PVA were 0.4, 2.1 and 1.0, respectively, around normothermia. We conclude that the temperature-dependent processes of cross-bridge cycling and Ca2+handling integratively depress Emaxand augment its oxygen cost without affecting the oxygen cost of PVA as myocardial temperature increases by 10°C around normothermia.

Increased afterload intensifies asynchronous wall motion and impairs ventricular relaxation

1993 ◽  
Vol 75 (1) ◽  
pp. 389-396 ◽  
Author(s):  
T. Miura ◽  
V. Bhargava ◽  
B. D. Guth ◽  
K. S. Sunnerhagen ◽  
S. Miyazaki ◽  
...  
Keyword(s):  
Angiotensin Ii ◽  
Wall Motion ◽  
Left Ventricular Pressure ◽  
Left Ventricular ◽  
Apical Region ◽  
Left Ventricular Relaxation ◽  
Ventricular Relaxation ◽  
Pressure Time ◽  
Contrast Ventriculography ◽  
Temporal Dispersion

To clarify whether impaired left ventricular relaxation elicited by increased afterload is attributable to regional dyssynchrony, we analyzed in dogs simultaneous left ventricular contrast ventriculography and pressure before and during angiotensin II infusion. Regional shortening was measured by a centerline method and a video-intensity method that served to define asynchronous motion. During angiotensin II, peak left ventricular pressure increased 35 +/- 6 mmHg, and the isovolumic pressure time constant (tau) was prolonged from 32.7 +/- 4.1 to 39.2 +/- 7.6 ms (P < 0.01). During increased afterload, early diastolic asynchrony, confined to the apical (5 of 7) and inferior regions (2 of 7), was detected in all dogs. Early systolic asynchrony was detected in the apical (5 of 7) and inferior (1 of 7) regions in six dogs. At control, systolic excursion was lower in the anteroapical than in the anterobasal region (P < 0.05). During angiotensin II, excursion of all regions was reduced, with the apical region lower than other regions (P < 0.01). In the normal dog heart, impaired relaxation with augmented afterload is coincident with asynchronous wall motion, especially in the apical-inferior region. Temporal dispersion of regional contraction may explain delayed left ventricular relaxation associated with increased afterload.

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