BACKGROUND: The time constant of left ventricular (LV) relaxation derived from a monoexponential model has been widely used as an index of LV relaxation rate or lusitropism, although this model has several well-recognized problems. In the present study, we proposed a logistic model and derived a "logistic" time constant (TL) as a better alternative to the conventional "exponential" time constant (TE). METHODS AND RESULTS: A total of 189 beats (147 isovolumic and 42 ejecting beats) were investigated in seven canine excised cross-circulated heart preparations. We found that the logistic model fitted much more precisely all the observed LV isovolumic relaxation pressure-time [P(t)] curves than the monoexponential model (P < .05). The logistic model also fitted well both the time curve of the first derivative of the observed P(t) (dP/dt) and the dP/dt-P(t) phase-plane curve. Like TE, TL indicated that volume loading depressed LV lusitropism and that increasing heart rate and ejection fraction augmented it. TL was independent of the choice of cutoff point defining the end of isovolumic relaxation; TE was dependent on that choice. CONCLUSIONS: 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.
BACKGROUND: The time constant of left ventricular (LV) relaxation derived from a monoexponential model has been widely used as an index of LV relaxation rate or lusitropism, although this model has several well-recognized problems. In the present study, we proposed a logistic model and derived a "logistic" time constant (TL) as a better alternative to the conventional "exponential" time constant (TE). METHODS AND RESULTS: A total of 189 beats (147 isovolumic and 42 ejecting beats) were investigated in seven canine excised cross-circulated heart preparations. We found that the logistic model fitted much more precisely all the observed LV isovolumic relaxation pressure-time [P(t)] curves than the monoexponential model (P < .05). The logistic model also fitted well both the time curve of the first derivative of the observed P(t) (dP/dt) and the dP/dt-P(t) phase-plane curve. Like TE, TL indicated that volume loading depressed LV lusitropism and that increasing heart rate and ejection fraction augmented it. TL was independent of the choice of cutoff point defining the end of isovolumic relaxation; TE was dependent on that choice. CONCLUSIONS: 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.
Authors: Candelas Pérez Del Villar; Javier Bermejo; Daniel Rodríguez-Pérez; Pablo Martínez-Legazpi; Yolanda Benito; J Carlos Antoranz; M Mar Desco; Juan E Ortuño; Alicia Barrio; Teresa Mombiela; Raquel Yotti; Maria J Ledesma-Carbayo; Juan C Del Álamo; Francisco Fernández-Avilés Journal: Cardiovasc Res Date: 2015-02-17 Impact factor: 10.787
Authors: Leslie M Ogilvie; Brittany A Edgett; Jason S Huber; Mathew J Platt; Hermann J Eberl; Sohrab Lutchmedial; Keith R Brunt; Jeremy A Simpson Journal: Am J Physiol Heart Circ Physiol Date: 2020-03-27 Impact factor: 4.733
Authors: Shahryar M Chowdhury; Suma P Goudar; G Hamilton Baker; Carolyn L Taylor; Girish S Shirali; Mark K Friedberg; Andreea Dragulescu; Karen S Chessa; Luc Mertens Journal: Pediatr Cardiol Date: 2016-09-21 Impact factor: 1.655