Cardiac Energetics

Han, June‐Chiew; Tran, Kenneth; Taberner, Andrew J.; Chapman, B.J.; Loiselle, Denis S.

doi:10.1016/b978-0-12-814593-7.00023-2

Cited by 5 publications

(6 citation statements)

References 163 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…During twitch force production, a portion of the energy is used for cellular Ca 2+ handling, and is accompanied by release of heat, which is coined 'activation heat' (Gibbs et al, 1988;Han et al, 2019b). The heat release comes from i) ATP hydrolysis by transmembrane transporters to remove Ca 2+ from the cytosol following Ca 2+ -induced Ca 2+ release, and ii) ATP replenishment from mitochondrial oxidative phosphorylation.…”

Section: Introductionmentioning

confidence: 99%

Resolving an inconsistency in the estimation of the energy for excitation of cardiac muscle contraction

Han,

Pham,

Taberner

et al. 2023

Front. Physiol.

View full text Add to dashboard Cite

In the excitation of muscle contraction, calcium ions interact with transmembrane transporters. This process is accompanied by energy consumption and heat liberation. To quantify this activation energy or heat in the heart or cardiac muscle, two non-pharmacological approaches can be used. In one approach using the “pressure-volume area” concept, the same estimate of activation energy is obtained regardless of the mode of contraction (either isovolumic/isometric or ejecting/shortening). In the other approach, an accurate estimate of activation energy is obtained only when the muscle contracts isometrically. If the contraction involves muscle shortening, then an additional component of heat associated with shortening is liberated, over and above that of activation. The present study thus examines the reconcilability of the two approaches by performing experiments on isolated muscles measuring contractile force and heat output. A framework was devised from the experimental data to allow us to replicate several mechanoenergetics results gleaned from the literature. From these replications, we conclude that the choice of initial muscle length (or ventricular volume) underlies the divergence of the two approaches in the estimation of activation energy when the mode of contraction involves shortening (ejection). At low initial muscle lengths, the heat of shortening is relatively small, which can lead to the misconception that activation energy is contraction mode independent. In fact, because cardiac muscle liberates heat of shortening when allowed to shorten, estimation of activation heat must be performed only under isometric (isovolumic) contractions. We thus recommend caution when estimating activation energy using the “pressure-volume area” concept.

show abstract

Section: Introductionmentioning

confidence: 99%

Resolving an inconsistency in the estimation of the energy for excitation of cardiac muscle contraction

Han,

Pham,

Taberner

et al. 2023

Front. Physiol.

View full text Add to dashboard Cite

show abstract

“…Suga even exploited his ‘pressure–volume area’ concept to derive mechanical efficiency as a function of preload and afterload (Suga et al., 1985 ). We have recently provided further evidence (Loiselle et al., 2021 ) that so‐called ‘Suga's efficiency’ is thermodynamically flawed given the physiological untenability of Suga's ‘potential energy’ term (Han, Taberner, Tran, Gao et al., 2012 ; Han, Taberner, Tran, Nickerson et al., 2012 ; Han, Tran et al., 2019 ).…”

Section: Discussionmentioning

confidence: 99%

Cardiac efficiency and Starling's Law of the Heart

Han

Taberner

Loiselle

et al. 2022

The Journal of Physiology

Self Cite

View full text Add to dashboard Cite

show abstract

“…Myocardial O 2 consumption

is linked to cardiac mechanical power by the energetic equivalent of O 2 for the myocardium EE (Han et al, 2019 ):

…”

Section: Methodsmentioning

confidence: 99%

“…Myocardial O 2 consumption

({\dot{normalV} O}_{2})

is linked to cardiac mechanical power by the energetic equivalent of O 2 for the myocardium EE (Han et al, 2019):

\begin{matrix} left \overset{V}{true} O_{2} = EE \times ({\overset{W}{true}}_{LV} + {\overset{W}{true}}_{RV}) = EE \times HR \times SV \times ()(, PejAo + PejPa) \end{matrix}

…”

Section: Methodsmentioning

confidence: 99%

Modeling the oxygen transport to the myocardium at maximal exercise at high altitude

Richalet

Hermand

2022

Physiological Reports

View full text Add to dashboard Cite

Exposure to high altitude induces a decrease in oxygen pressure and saturation in the arterial blood, which is aggravated by exercise. Heart rate (HR) at maximal exercise decreases when altitude increases in prolonged exposure to hypoxia. We developed a simple model of myocardial oxygenation in order to demonstrate that the observed blunting of maximal HR at high altitude is necessary for the maintenance of a normal myocardial oxygenation. Using data from the available scientific literature, we estimated the myocardial venous oxygen pressure and saturation at maximal exercise in two conditions: (1) with actual values of maximal HR (decreasing with altitude); ( 2) with sea-level values of maximal heart rate, whatever the altitude (no change in HR). We demonstrated that, in the absence of autoregulation of maximal HR, myocardial tissue oxygenation would be incompatible with life above 6200 m-7600 m, depending on the hypothesis concerning a possible increase in coronary reserve (increase in coronary blood flow at exercise). The decrease in maximal HR at high altitude could be explained by several biological mechanisms involving the autonomic nervous system and its receptors on myocytes. These experimental and clinical observations support the hypothesis that there exists an integrated system at the cellular level, which protects the myocardium from a hazardous disequilibrium between O 2 supply and O 2 consumption at high altitude.

show abstract

Cardiac Energetics

Cited by 5 publications

References 163 publications

Resolving an inconsistency in the estimation of the energy for excitation of cardiac muscle contraction

Resolving an inconsistency in the estimation of the energy for excitation of cardiac muscle contraction

Cardiac efficiency and Starling's Law of the Heart

Modeling the oxygen transport to the myocardium at maximal exercise at high altitude

Contact Info

Product

Resources

About