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Exercise induced bradycardia

Alicia D'Souza, Charles M Pearman, Yanwen Wang, Shu Nakao, Sunil Jit R Logantha, Charlotte Cox, Hayley J Bennett, Yu Zhang, Anne Berit Johnsen, Nora Linscheid, Pi C Poulsen, Jonathan Elliott, Jessica Coulson, Jamie S McPhee, Abigail C Robertson, Paula A da Costa Martins, Ashraf Kitmitto, Ulrik Wisloff, Elizabeth J Cartwright, Oliver Monfredi, Alicia Lundby, Halina Dobrzynski, Delvac Oceandy, Gwilym M Morris, Mark R Boyett
Rationale: Downregulation of the pacemaking ion channel, HCN4, and the corresponding ionic current, If, underlies exercise training-induced sinus bradycardia in rodents. If this occurs in humans, it could explain the increased incidence of bradyarrhythmias in veteran athletes and it will be important to understand the underlying processes. Objective: To test the role of HCN4 in the training-induced bradycardia in human athletes and investigate the role of micro-RNAs (miRs) in the repression of HCN4. Methods and Results: As in rodents, the intrinsic heart rate was significantly lower in human athletes than non-athletes and in all subjects the rate-lowering effect of the HCN selective blocker, ivabradine, was significantly correlated with the intrinsic heart rate, consistent with HCN repression in athletes...
August 17, 2017: Circulation Research
Mark R Boyett, Yanwen Wang, Shu Nakao, Jonathan Ariyaratnam, George Hart, Oliver Monfredi, Alicia D'Souza
July 6, 2017: Journal of Applied Physiology
Mark R Boyett, Yanwen Wang, Shu Nakao, Jonathan Ariyaratnam, George Hart, Oliver Monfredi, Alicia D'Souza, George E Billman
April 6, 2017: Journal of Applied Physiology
Eduard Guasch, Lluís Mont
The cardiovascular benefits of physical activity are indisputable. Nevertheless, growing evidence suggests that both atrial fibrillation and right ventricular arrhythmia can be caused by intense exercise in some individuals. Exercise-induced atrial fibrillation is most commonly diagnosed in middle-aged, otherwise healthy men who have been engaged in endurance training for >10 years, and is mediated by atrial dilatation, parasympathetic enhancement, and possibly atrial fibrosis. Cardiac ablation is evolving as a first-line tool for athletes with exercise-induced arrhythmia who are eager to remain active...
February 2017: Nature Reviews. Cardiology
Lan Zheng, Qiu Fang Li, Liu Ni, Hui Wang, Xiang Cheng Ruan, Xiu Shan Wu
We used Drosophila melanogaster as an animal model system to study the impact of exercise training initiated early in life on cardiac function using a well-established model of inherent myogenic properties of the heart and discussed the changes on myosin, a myocardial contractile protein. We also explored the effect of early physical exercise on organismal aging by analyzing the wake-sleep pattern using a Drosophila activity monitor system. We found that a variety of arrhythmias are part of the heart spectrum in old flies after a lifetime of physical exercise as evidenced by reducing the incidence of fibrillations and increasing the occurrence of bradycardias...
October 27, 2016: Biogerontology
Moreshwar S Desai, Bhoomika Mathur, Zeena Eblimit, Hernan Vasquez, Heinrich Taegtmeyer, Saul J Karpen, Daniel J Penny, David D Moore, Sayeepriyadarshini Anakk
Cardiac dysfunction in patients with liver cirrhosis is strongly associated with increased serum bile acid concentrations. Here we show that excess bile acids decrease fatty acid oxidation in cardiomyocytes and can cause heart dysfunction, a cardiac syndrome that we term cholecardia. Farnesoid X receptor; Small Heterodimer Partner double knockout mice, a model for bile acid overload, display cardiac hypertrophy, bradycardia, and exercise intolerance. In addition, double knockout mice exhibit an impaired cardiac response to catecholamine challenge...
January 2017: Hepatology: Official Journal of the American Association for the Study of Liver Diseases
Natale Daniele Brunetti, Pier Luigi Pellegrino, Girolamo D'Arienzo, Rafel Sai, Luigi Ziccardi, Francesco Santoro, Antonio Gaglione, Matteo Di Biase
We report the case of a 38-year-old woman with history of syncope and polymorphic ventricular tachycardia; tachycardia was inducible at exercise stress test, not at electrophysiologic study. Phases of QT prolongation were found at ambulatory electrocardiogram monitoring. The woman came to our attention for periodic control of implantable loop recorder. Rest electrocardiogram at admission unexpectedly showed sinus bradycardia, junctional rhythm, and ventricular premature beats. Furthermore, loop recorder control revealed a short run of bidirectional tachycardia, not associated with syncope...
November 2016: Journal of Electrocardiology
Sunil Jit R J Logantha, Mathis K Stokke, Andrew J Atkinson, Sanjay R Kharche, Sajida Parveen, Yawer Saeed, Ivar Sjaastad, Ole M Sejersted, Halina Dobrzynski
BACKGROUND: The sarcoplasmic reticulum Ca(2+)-ATPase (SERCA2) pump is an important component of the Ca(2+)-clock pacemaker mechanism that provides robustness and flexibility to sinus node pacemaking. We have developed transgenic mice with reduced cardiac SERCA2 abundance (Serca2 KO) as a model for investigating SERCA2's role in sinus node pacemaking. METHODS AND RESULTS: In Serca2 KO mice, ventricular SERCA2a protein content measured by Western blotting was 75% (P < 0...
2016: Frontiers in Physiology
Carsten Walter Israel
Bradyarrhythmias cause symptoms such as syncope, dizziness, or exercise intolerance and lead to the implantation of > 100 000 pacemakers in Germany annually. They are caused either by sinus node dysfunction (sinus bradycardia, sinoatrial block, sinusarrest, preautomatic pauses in paroxysmal atrial fibrillation, chronotropic incompetence) or by atrioventricular (AV) conduction abnormalities (AV block, complex bundle branch block). Optimal therapy of bradycardia crucially depends on ECG documentation which frequently requires Holter monitoring in the case of intermittent bradycardia...
May 2016: Deutsche Medizinische Wochenschrift
Sarah E Petite, Bryan M Bishop, Vincent F Mauro
The pharmacology, pharmacokinetics, efficacy and safety of ivabradine are reviewed. Ivabradine is an oral medication that directly and selectively inhibits the hyperpolarization-activated cyclic-nucleotide gated funny (If) current in the sinoatrial node resulting in heart rate reduction. It has a plasma elimination half-life of 6 hours and is administered twice daily. Ivabradine is extensively metabolized by cytochrome P450 3A4, and its metabolism is affected by inducers and inhibitors of the 3A4 enzyme. Studies in patients with heart failure indicate that ivabradine improves surrogate markers such as exercise tolerance...
February 23, 2016: American Journal of Therapeutics
D M Porteiro Vázquez, M Perego, L Santos, M Gerou-Ferriani, M W S Martin, R A Santilli
OBJECTIVES: To document the electrocardiographic findings of vagally-induced paroxysmal atrial fibrillation following a presumed reflex syncopal episode in the dog. ANIMALS: Seven dogs with a syncopal episode followed by a paroxysm of atrial fibrillation recorded on a 24-hour Holter. METHODS: Twenty-four hour Holter monitors were retrospectively reviewed, analysing the cardiac rhythm associated with syncopal events. Each recording was analysed from 10 min before the syncopal episode to until 10 min after a normal sinus rhythm had returned...
March 2016: Journal of Veterinary Cardiology: the Official Journal of the European Society of Veterinary Cardiology
Pâmela Santana Daltro, Paula Santana Alves, Murilo Fagundes Castro, Carine M Azevedo, Juliana Fraga Vasconcelos, Kyan James Allahdadi, Luiz Antônio Rodrigues de Freitas, Bruno Solano de Freitas Souza, Ricardo Ribeiro Dos Santos, Milena Botelho Pereira Soares, Simone Garcia Macambira
BACKGROUND/OBJECTIVES: High fat diet (HFD) is a major contributor to the development of obesity and cardiovascular diseases due to the induction of cardiac structural and hemodynamic abnormalities. We used a model of diabetic cardiomyopathy in C57Bl/6 mice fed with a HFD to investigate the effects of granulocyte-colony stimulating factor (G-CSF), a cytokine known for its beneficial effects in the heart, on cardiac anatomical and functional abnormalities associated with obesity and type 2 diabetes...
2015: BMC Cardiovascular Disorders
Daphne M Mulders, Cecile C de Vos, Ilse Vosman, Michel J A M van Putten
PURPOSE: Vagus nerve stimulation (VNS) has been successfully applied to reduce seizure frequency in numerous patients with epilepsy. However, various side effects, including dyspnea and bradycardia have been reported, that appear exercise related in some patients. This pilot study aims to obtain insight in the cardiorespiratory effects of VNS during both rest and exercise. METHODS: Patients with a VNS device who experience side effects during exercise are compared with patients without side effects...
December 2015: Seizure: the Journal of the British Epilepsy Association
Iris del Castillo Velasco-Martínez, Claudia J Hernández-Camacho, Lía C Méndez-Rodríguez, Tania Zenteno-Savín
In mammalian tissues under hypoxic conditions, ATP degradation results in accumulation of purine metabolites. During exercise, muscle energetic demand increases and oxygen consumption can exceed its supply. During breath-hold diving, oxygen supply is reduced and, although oxygen utilization is regulated by bradycardia (low heart rate) and peripheral vasoconstriction, tissues with low blood flow (ischemia) may become hypoxic. The goal of this study was to evaluate potential differences in the circulating levels of purine metabolism components between diving and exercise in bottlenose dolphins (Tursiops truncatus)...
January 2016: Comparative Biochemistry and Physiology. Part A, Molecular & Integrative Physiology
Laiali Jurdi Chaar, Tatiana Pereira Alves, Alvaro Martins Batista Junior, Lisete Compagno Michelini
BACKGROUND: Exercise training (T) blunts functional deficits and renin-angiotensin system (RAS) hyperactivity in hypertensive individuals. There is no information on T-induced temporal changes of brain RAS. We evaluate now the simultaneous effects of T on functional responses and time course changes in the expression/activity of brain RAS components in autonomic cardiovascular-controlling areas. METHODS AND RESULTS: Spontaneously hypertensive rats (SHR) and age-matched normotensive controls (WKY) were trained for 0, 1, 2, 4, 8 and 12 weeks...
2015: PloS One
Sylvia Konstantinidou, Helen Soultanakis
Apnea after exercise may evoke a neurally mediated conflict that may affect apneic time and create a cardiovascular strain. The physiological responses, induced by apnea with face immersion in cold water (10 °C), after a 3-min exercise bout, at 85% of VO2max,were examined in 10 swimmers. A pre-selected 40-s apnea, completed after rest (AAR), could not be met after exercise (AAE), and was terminated with an agonal gasp reflex, and a reduction of apneic time, by 75%. Bradycardia was evident with immersion after both, 40-s of AAR and after AAE (P<0...
January 2016: Respiratory Physiology & Neurobiology
Eugen Brailoiu, Elena Deliu, Romeo A Sporici, G Cristina Brailoiu
Irisin is a newly identified hormone induced in muscle and adipose tissues by physical activity. This protein and its encoding gene have been identified in the brain; in addition, the precursor for irisin, FNDC5, can cross the blood-brain barrier. The fact that irisin is secreted during exercise together with the lower resting heart rate in athletes prompted us to investigate the effect of irisin on cardiac-projecting vagal neurons of nucleus ambiguus, a key regulatory site of heart rate. In vitro experiments in cultured nucleus ambiguus neurons indicate that irisin activates these neurons, inducing an increase in cytosolic Ca(2+) concentration and neuronal depolarization...
June 2015: Physiological Reports
Tamás Erdei, Svend Aakhus, Paolo Marino, Walter J Paulus, Otto A Smiseth, Alan G Fraser
Cardiopulmonary functional reserve measured as peak oxygen uptake is predicted better at rest by measures of cardiac diastolic function than by systolic function. Normal adaptations in the trained heart include resting bradycardia, increased LV end-diastolic volume and augmented early diastolic suction on exercise. In normal populations early diastolic relaxation declines with age and end-diastolic stiffness increases, but in healthy older subjects who have exercised throughout their lives diastolic function can be well preserved...
September 2015: Heart: Official Journal of the British Cardiac Society
Juliane Cruz Campos, Tiago Fernandes, Luiz Roberto Grassmann Bechara, Nathalie Alves da Paixão, Patricia Chakur Brum, Edilamar Menezes de Oliveira, Julio Cesar Batista Ferreira
BACKGROUND: We previously reported that exercise training (ET) facilitates the clearance of damaged proteins in heart failure. Here, we characterized the impact of ET on cardiac protein quality control during compensated ventricular hypertrophy in spontaneously hypertensive rats (SHR). METHODS AND RESULTS: SHR were randomly assigned into sedentary and swimming-trained groups. Sedentary SHR displayed cardiac hypertrophy with preserved ventricular function compared to normotensive rats, characterizing a compensated cardiac hypertrophy...
2015: Oxidative Medicine and Cellular Longevity
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