American journal of physiology. Heart and circulatory physiology
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Am. J. Physiol. Heart Circ. Physiol. · May 2012
The "systolic volume balance" method for the noninvasive estimation of cardiac output based on pressure wave analysis.
Cardiac output (CO) monitoring is essential for the optimal management of critically ill patients. Several mathematical methods have been proposed for CO estimation based on pressure waveform analysis. Most of them depend on invasive recording of blood pressure and require repeated calibrations, and they suffer from decreased accuracy under specific conditions. ⋯ The difference of SVB-derived CO from model CO (for brachial waves) was 0.042 ± 0.341 l/min, and the limits of agreement were -0.7 to 0.6 l/min, indicating high accuracy. The intraclass correlation coefficient and root mean square error between estimated and "real" CO were 0.861 and 0.041 l/min, respectively, indicating very good accuracy. eSVB also provided accurate estimation of CO. An in vivo validation study of the proposed methods remains to be conducted.
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Am. J. Physiol. Heart Circ. Physiol. · May 2012
Modulation of SR Ca2+ release by the triadin-to-calsequestrin ratio in ventricular myocytes.
Calsequestrin (CSQ) is a Ca(2+) storage protein that interacts with triadin (TRN), the ryanodine receptor (RyR), and junctin (JUN) to form a macromolecular tetrameric Ca(2+) signaling complex in the cardiac junctional sarcoplasmic reticulum (SR). Heart-specific overexpression of CSQ in transgenic mice (TG(CSQ)) was associated with heart failure, attenuation of SR Ca(2+) release, and downregulation of associated junctional SR proteins, e.g., TRN. Hence, we tested whether co-overexpression of CSQ and TRN in mouse hearts (TG(CxT)) could be beneficial for impaired intracellular Ca(2+) signaling and contractile function. ⋯ Echocardiographic and hemodynamic measurements revealed a depressed cardiac performance after isoproterenol application in TG(CxT) compared with TG(CSQ). Our results suggest that co-overexpression of CSQ and TRN led to a normalization of the SR Ca(2+) release compared with TG(CSQ) mice but a depressed contractile function and survival rate probably due to cardiac fibrosis, a lower SERCA2a expression, and a blunted response to β-adrenergic stimulation. Thus the TRN-to-CSQ ratio is a critical modulator of the SR Ca(2+) signaling.
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Am. J. Physiol. Heart Circ. Physiol. · May 2012
Clinical TrialTwo weeks of muscle immobilization impairs functional sympatholysis but increases exercise hyperemia and the vasodilatory responsiveness to infused ATP.
During exercise, contracting muscles can override sympathetic vasoconstrictor activity (functional sympatholysis). ATP and adenosine have been proposed to play a role in skeletal muscle blood flow regulation. However, little is known about the role of muscle training status on functional sympatholysis and ATP- and adenosine-induced vasodilation. ⋯ Training increased skeletal muscle P2Y2 receptor content (P < 0.05), whereas it did not change with immobilization. These results suggest that muscle inactivity impairs functional sympatholysis and that the magnitude of hyperemia and blood pressure response to exercise is dependent on the training status of the muscle. Immobilization also increases the vasodilatory response to infused ATP.
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Am. J. Physiol. Heart Circ. Physiol. · Apr 2012
Cardiac-specific genetic inhibition of nuclear factor-κB prevents right ventricular hypertrophy induced by monocrotaline.
Uncontrolled pulmonary arterial hypertension (PAH) results in right ventricular (RV) hypertrophy (RVH), progressive RV failure, and low cardiac output leading to increased morbidity and mortality (McLaughlin VV, Archer SL, Badesch DB, Barst RJ, Farber HW, Lindner JR, Mathier MA, McGoon MD, Park MH, Rosenson RS, Rubin LJ, Tapson VF, Varga J. J Am Coll Cardiol 53: 1573-1619, 2009). Although the exact figures of its prevalence are difficult to obtain because of the diversity of identifiable causes, it is estimated that the incidence of pulmonary hypertension is seven to nine cases per million persons in the general population and is most prevalent in the age group of 20-40, occurring more commonly in women than in men (ratio: 1.7 to 1; Rubin LJ. ⋯ Despite major advances in the understanding of the pathogenesis of PAH, the molecular mechanism(s) by which PAH promotes RVH and cardiac failure still remains elusive. Of all the mechanisms involved in the pathogenesis, inflammation and oxidative stress remain the core of the etiology of PAH that leads to development of RVH (Dorfmüller P, Perros F, Balabanian K, Humbert M. Eur Respir J 22: 358-363, 2003).
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Am. J. Physiol. Heart Circ. Physiol. · Apr 2012
A coupled hydrodynamic model of the cardiovascular and cerebrospinal fluid system.
Coupling of the cardiovascular and cerebrospinal fluid (CSF) system is considered to be important to understand the pathophysiology of cerebrovascular and craniospinal disease and intrathecal drug delivery. A coupled cardiovascular and CSF system model was designed to examine the relation of spinal cord (SC) blood flow (SCBF) and CSF pulsations along the spinal subarachnoid space (SSS). A one-dimensional (1-D) cardiovascular tree model was constructed including a simplified SC arterial network. ⋯ The properties and anatomy of the SC arterial network and SSS were found to have an important impact on pressure and flow and perivascular fluid movement to the SC. Overall, the coupled model provides predictions about the flow and pressure environment in the SC and SSS. More detailed measurements are needed to fully validate the model.