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Source: American Journal of Physiology. Heart and Circulatory Physiology

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Total 253 results found since Jan 2013.

Human Fetal Hearts with Tetralogy of Fallot have Altered Fluid Dynamics and Forces.
In this study, we performed patient-specific ultrasound-based flow simulations of 3 TOF and 7 normal human fetal hearts. TOF right ventricles (RV) had smaller end-diastolic volumes (EDV) but similar stroke volumes (SV), while TOF left ventricles (LV) had similar EDV but slightly increased SV compared to normal ventricles. Simulation showed that TOF ventricles had elevated systolic intra-ventricular pressure gradient (IVPG), and required additional energy for ejection, but IVPG elevations were considered to be mild relative to arterial pressure. TOF RV and LV had similar pressures due to equalization via ventricular septal ...
Source: American Journal of Physiology. Heart and Circulatory Physiology - September 14, 2018 Category: Physiology Authors: Wiputra H, Chen CK, Talbi E, Lim GL, Soomar SM, Biswas A, Mattar CNZ, Bark D, Leo HL, Yap CH Tags: Am J Physiol Heart Circ Physiol Source Type: research

Post Stroke Cognitive Impairment and Hippocampal Neurovascular Remodeling: The Impact of Diabetes and Sex.
Abstract Diabetes increases the risk and severity of cognitive impairment, especially after ischemic stroke. Pathological remodeling of the cerebrovasculature has been postulated to contribute to poor neuronal repair and worsened cognitive deficits in diabetes. However, little is known about the effect of diabetes on the vascularization of hippocampus, a domain critical to memory and learning. Therefore we had two aims for this study: 1) to determine the impact of diabetes on hippocampal neurovascular remodeling and the resulting cognitive impairment after stroke using two models with varying disease severity, and...
Source: American Journal of Physiology. Heart and Circulatory Physiology - August 17, 2018 Category: Physiology Authors: Ward R, Valenzuela JP, Li W, Dong G, Fagan SC, Ergul A Tags: Am J Physiol Heart Circ Physiol Source Type: research

Age-Dependent Cardiac Function during Experimental Sepsis: Effect of Pharmacological Activation of AMP-Activated Protein Kinase by AICAR.
Abstract Age represents a major risk factor of multiple organ failure, including cardiac dysfunction, in patients with sepsis. AMP-activated protein kinase (AMPK) is a crucial regulator of energy homeostasis, which controls mitochondrial biogenesis by activation of peroxisome proliferator-activated receptor-γ co-activator-α and disposal of defective organelles by autophagy. We investigated whether AMPK dysregulation contributes to age-dependent cardiac injury in young (2-3 months) and mature adult (11-13 months) male mice subjected to sepsis by cecal ligation and puncture, and whether AMPK activation by 5-amino-...
Source: American Journal of Physiology. Heart and Circulatory Physiology - July 6, 2018 Category: Physiology Authors: Inata Y, Piraino G, Hake PW, O'Connor M, Lahni P, Wolfe V, Schulte C, Moore V, James JM, Zingarelli B Tags: Am J Physiol Heart Circ Physiol Source Type: research

No-reflow Phenomenon in Heart and Brain.
Abstract The no-reflow phenomenon refers to the observation that when an organ is made ischemic by occlusion of a large artery supplying it, restoration of patency in that artery does not restore perfusion to the microvasculature supplying the parenchyma of that organ. This has been observed following prolonged arterial occlusions in the heart (30 to 90 minutes), brain, skin, and kidney. In experimental models, zones of no-reflow in the heart are characterized by ultrastructural microvascular damage, including focal endothelial swelling obstructing the lumen of small vessels. Blood elements such as neutrophil plug...
Source: American Journal of Physiology. Heart and Circulatory Physiology - June 8, 2018 Category: Physiology Authors: Kloner RA, King KS, Harrington M Tags: Am J Physiol Heart Circ Physiol Source Type: research

Exercise cardiac MRI unmasks right ventricular dysfunction in acute hypoxia and chronic pulmonary arterial hypertension.
Conclusions - Non-invasive cardiac imaging during exercise unmasks depleted RV contractile reserves in healthy adults under hypoxic conditions and PAH patients under normoxic conditions despite preserved ejection fraction. PMID: 29775415 [PubMed - as supplied by publisher]
Source: American Journal of Physiology. Heart and Circulatory Physiology - May 18, 2018 Category: Physiology Authors: Jaijee SK, Quinlan M, Tokarczuk P, Clemence M, Howard LS, Gibbs JSR, O'Regan D Tags: Am J Physiol Heart Circ Physiol Source Type: research

Hemodynamic effects of incremental lung hyperinflation.
Abstract Dynamic hyperinflation (DH) is common in COPD and is associated with dyspnea and exercise intolerance. DH also has adverse cardiac effects, though the magnitude of DH and the mechanisms responsible for the hemodynamic impairment remain unclear. We hypothesized that incrementally increasing DH would systematically reduce left-ventricular (LV) end diastolic volume (LVEDV) and stroke volume (LVSV) due to direct ventricular interaction (DVI). Twenty-three healthy subjects (22{plus minus}2yrs) were exposed to varying degrees of expiratory loading to induce DH such that inspiratory capacity (IC) was decreased b...
Source: American Journal of Physiology. Heart and Circulatory Physiology - May 4, 2018 Category: Physiology Authors: Cheyne WS, Gelinas JCM, Eves ND Tags: Am J Physiol Heart Circ Physiol Source Type: research

Dynamic cerebral autoregulation is impaired during sub-maximal isometric handgrip in patients with heart failure.
CONCLUSIONS: HF patients are more likely to have impaired dCA during iHG in comparison with age-matched controls. Our results also suggest an impairment of myogenic, neurogenic and metabolic control mechanisms in HF. The relationship between impaired dCA and neurological complications in HF patients during exercise deserves further investigation. PMID: 29652541 [PubMed - as supplied by publisher]
Source: American Journal of Physiology. Heart and Circulatory Physiology - April 13, 2018 Category: Physiology Authors: Caldas JR, Panerai RB, Salinet ASM, Bor-Seng-Shu E, Galas FRBG, Ferreira GSR, Camara L, Passos RH, Almeida JP, Nogueira RC, Oliveira M ML, Robinson TG, Hajjar LA Tags: Am J Physiol Heart Circ Physiol Source Type: research

Cardiorespiratory interactions in humans and animals: Rhythms for life.
Abstract The cardiorespiratory system exhibits oscillations from a range of sources. One of the most studied oscillations is heart rate variability, which is thought to be beneficial and can serve as an index of a healthy cardiovascular system. Heart rate variability is dampened in many diseases including depression, autoimmune diseases, hypertension and heart failure. Thus, understanding the interactions that lead to heart rate variability, and its physiological role, could help with prevention, diagnosis and treatment of cardiovascular diseases. In this review we consider three types of cardiorespiratory interac...
Source: American Journal of Physiology. Heart and Circulatory Physiology - March 9, 2018 Category: Physiology Authors: Elstad M, O'Callaghan EL, Smith AJ, Ben-Tal A, Ramchandra R Tags: Am J Physiol Heart Circ Physiol Source Type: research

Sympathetically-mediated cardiac responses to isolated muscle metaboreflex activation following exercise are modulated by body position in humans.
Abstract Isolated muscle metaboreflex activation with post-handgrip exercise ischemia (PEI) increases sympathetic nerve activity and partially maintains the exercise-induced increase in blood pressure, but a smaller heart rate (HR) response occurs. The cardiopulmonary baroreceptors, mechanically sensitive receptors that respond to changes in central blood volume and pressure, are strongly associated with changes in body position and upon activation elicit reflex sympathoinhibition. Here, we tested the hypothesis that postural changes modulate the sympathetically-mediated cardiac response to PEI in humans. Beat-to-...
Source: American Journal of Physiology. Heart and Circulatory Physiology - December 15, 2017 Category: Physiology Authors: Teixeira AL, Daher M, Souza M, Ramos PS, Fisher JP, Vianna LC Tags: Am J Physiol Heart Circ Physiol Source Type: research

Metaboreflex-mediated hemodynamic abnormalities in individuals with coronary artery disease without overt signs or symptoms of heart failure.
This study was devised to investigate the effect of coronary artery disease (CAD) without overt signs of heart failure on the cardiovascular responses to muscle metaboreflex activation. We hypothesized that any CAD-induced pre-clinical systolic and/or diastolic dysfunction could impair hemodynamic response to the metaboreflex test. Twelve males diagnosed with CAD without any sign or symptoms of heart failure and 11 age-matched healthy controls (CTL) participated in the study. Subjects performed a post-exercise muscle ischemia (PEMI) test to activate the metaboreflex. They also performed a control exercise-recovery test to ...
Source: American Journal of Physiology. Heart and Circulatory Physiology - November 10, 2017 Category: Physiology Authors: Magnani S, Roberto S, Sainas G, Milia R, Palazzolo G, Cugusi L, Pinna V, Doneddu A, Hosseini Kakhak SA, Tocco F, Mercuro G, Crisafulli A Tags: Am J Physiol Heart Circ Physiol Source Type: research

The Sex-Specific Impact of Aging on the Blood Pressure Response to Exercise.
Abstract An exaggerated blood pressure (BP) response to exercise has been linked to cardiovascular disease (CVD), but little is known about the impact of age and sex on this response. Therefore, this study examined the hemodynamic and skeletal muscle metabolic response to dynamic plantar flexion exercise, at 40% of WRmax, in 40 physical activity-matched young (n=20, 23±1 yr) and old (n=20, 73±2 yr), equally distributed, male and female subjects. Central hemodynamics and BP (finometer), popliteal artery (PA) blood flow (Doppler ultrasound), and skeletal muscle metabolism (phosphorous magnetic resonance spectrosco...
Source: American Journal of Physiology. Heart and Circulatory Physiology - October 13, 2017 Category: Physiology Authors: Trinity JD, Layec G, Hart CR, Richardson RS Tags: Am J Physiol Heart Circ Physiol Source Type: research

Pulmonary vasodilation by phosphodiesterase 5-inhibition is enhanced and nitric oxide-independent in early pulmonary hypertension after myocardial infarction.
Abstract Myocardial infarction (MI) may result in pulmonary hypertension (PH). Inhibition of phosphodiesterase 5 (PDE5), the enzyme responsible for the breakdown of cGMP in vascular smooth muscle, has become part of the contemporary therapeutic armamentarium for pulmonary arterial hypertension and may also be of benefit in PH secondary to MI. Nitric oxide (NO) is an important source of cGMP and can be enhanced in early PH and decreased in severe PH. In the present study we investigated if PDE5-inhibition ameliorates pulmonary hemodynamics in swine with PH secondary to MI and whether NO is essential. The PDE5-inhib...
Source: American Journal of Physiology. Heart and Circulatory Physiology - October 6, 2017 Category: Physiology Authors: van Duin RWB, Houweling B, Uitterdijk A, Duncker DJ, Merkus D Tags: Am J Physiol Heart Circ Physiol Source Type: research

Muscle sympathetic nerve responses to passive and active one-legged cycling: Insight into the contributions of central command.
Abstract The contribution of central command to the peripheral vasoconstrictor response during exercise has been investigated using primarily handgrip exercise. The purpose of the present study was to compare muscle sympathetic nerve activity (MSNA) responses during passive (involuntary) and active (voluntary) zeroload cycling to gain insight into the effects of central command on sympathetic outflow during dynamic exercise. Hemodynamic measurements and contralateral leg MSNA (microneurography) were collected in eighteen young healthy participants at rest and during 2 minutes of passive and active zeroload one-leg...
Source: American Journal of Physiology. Heart and Circulatory Physiology - September 22, 2017 Category: Physiology Authors: Doherty CJ, Incognito AV, Notay K, Burns MJ, Slysz JT, Seed JD, Nardone M, Burr JF, Millar PJ Tags: Am J Physiol Heart Circ Physiol Source Type: research

The cerebro-cardiovascular response to periodic squat-stand maneuvers in healthy subjects: a time-domain analysis.
CONCLUSIONS: The changes of CBV subcomponents during repeated SSMs indicate a complex response of CBVms. to SSMs that can only be partially explained by myogenic mechanis More work is needed to clarify the potential contribution of other co-factors, such as breath-to-breath changes in pCO2, HR, stroke volume and the neurogenic component of dynamic CA. PMID: 28887332 [PubMed - as supplied by publisher]
Source: American Journal of Physiology. Heart and Circulatory Physiology - September 8, 2017 Category: Physiology Authors: Barnes SC, Ball N, Haunton VJ, Robinson TG, Panerai RB Tags: Am J Physiol Heart Circ Physiol Source Type: research

Carotid Artery Stenosis In Hypertensive Rats Impairs Dilatory Pathways In Parenchymal Arterioles.
Abstract Hypertension is a leading risk factor for vascular cognitive impairment and is strongly associated with carotid artery stenosis. In normotensive rats, chronic cerebral hypoperfusion induced by bilateral common carotid artery stenosis (BCAS) leads to cognitive impairment that is associated with impaired endothelium-dependent dilation in parenchymal arterioles (PAs). The aim of this study was to assess the effects of BCAS on PA function and structure in stroke prone spontaneously hypertensive rats (SHRSP), a model of human essential hypertension. Understanding the effects of hypoperfusion on the PAs in a hy...
Source: American Journal of Physiology. Heart and Circulatory Physiology - August 25, 2017 Category: Physiology Authors: Matin N, Fisher C, Jackson WF, Diaz-Otero JM, Dorrance AM Tags: Am J Physiol Heart Circ Physiol Source Type: research