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Ventricular depolarization

Marc D Lemoine, Tobias Krause, Jussi T Koivumäki, Maksymilian Prondzynski, Mirja L Schulze, Evaldas Girdauskas, Stephan Willems, Arne Hansen, Thomas Eschenhagen, Torsten Christ
BACKGROUND: Cardiac repolarization abnormalities in drug-induced and genetic long-QT syndrome may lead to afterdepolarizations and life-threatening ventricular arrhythmias. Human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) should help to overcome the limitations of animal models based on species differences in repolarization reserve. Here, we compared head-to-head the contribution of I Ks (long QT1) and I Kr (long QT2) on action potentials (APs) in human left ventricular (LV) tissue and hiPSC-CM-derived engineered heart tissue (EHT)...
July 2018: Circulation. Arrhythmia and Electrophysiology
Andrew L Wit
Afterdepolarizations cause triggered arrhythmias. One kind occurs after repolarization is complete, delayed afterdepolarizations (DADs). Another occurs as an interruption in repolarization, early afterdepolarizations (EADs). Afterdepolarizations initiate arrhythmias when they depolarize membrane potential to threshold potential for triggering action potentials. DADs usually occur mostly when Ca2+ in the sarcoplasmic reticulum (SR) is elevated. The SR leaks some of the Ca2+ into the myoplasm through Ca2+ release channels controlled by ryanodine receptors (RyR2) during diastole...
June 19, 2018: Pacing and Clinical Electrophysiology: PACE
Muhammad U Butt, Ripa Patel, Yousef H Darrat, Gustavo X Morales, Claude S Elayi
BACKGROUND Wolff-Parkinson-White (WPW) pattern is due to a pre-excitation leading to characteristic ECG changes in sinus rhythm as short PR interval, the presence of delta waves, wide QRS complexes, and potentially Q wave-T wave vector discordance (pseudo-infarct pattern). These later changes can mask the underlying ECG depolarizing solely through the His-Purkinje system. Our case highlights how the ECG of a WPW pattern with a pseudo-infarct pattern can in fact mask a true infarct on the underlying ECG without pre-excitation...
June 13, 2018: American Journal of Case Reports
Marc Strik, Sylvain Ploux, Peter R Huntjens, Uyên Châu Nguyên, Antionio Frontera, Romain Eschalier, Remi Dubois, Philippe Ritter, Nicholas Klotz, Kevin Vernooy, Michel Haïssaguerre, Harry J G M Crijns, Frits W Prinzen, Pierre Bordachar
BACKGROUND: Electrocardiographic mapping (ECM) expresses electrical substrate through magnitude and direction of the activation delay vector (ADV). We investigated to what extent the response to cardiac resynchronization therapy (CRT) is determined by baseline ADV and by ADV modification through CRT and optimization of left ventricular (LV) pacing site. METHODS: ECM was performed in 79 heart failure patients (4 RBBB, 12 QRS < 120 ms, 23 non-specific conduction delay [NICD] and 40 left bundle branch block [LBBB])...
June 6, 2018: International Journal of Cardiology
Hanan Sayed Mohamed Farghaly, Israa El-Sayed Mohamed Ashry, Mohammad Salem Hareedy
BACKGROUND: Toxic effects of digoxin may occur with normal therapeutic serum level. However, the underlying mechanisms are not fully understood. Nuclear factor kappa-B (NF-kB) is an important transcription factor in most organ systems and is often implicated in the harmful effects of cardiac injury. NF-kB promotes inflammatory responses, mediates adverse cardiac remodeling and has a function correlation with calcium. The voltage-gated L-type calcium channel CaV1.2 mediates the influx of Ca+2 into the cell in response to membrane depolarization...
June 6, 2018: Biomedicine & Pharmacotherapy, Biomédecine & Pharmacothérapie
Meiwei Zhang, Yeling Wang, Dongmei Chen, Hang Li, Zhiguo Zhang
RATIONALE: Dual atrioventricular nodal non-reentrant tachycardia (DAVNNT) is an uncommon arrhythmia. Because of the different refractory periods of fast and slow pathways, a single atrial depolarization gives rise to 2 ventricular activationsthrough fast and slow pathways separately. PATIENT CONCERNS: A 45-year-old woman was referred to our Cardiology Center with symptoms of recurrent palpitations and fatigue persisting for the previous 3 years. On echocardiography, the ejection fraction of the left ventricle was 45%...
June 2018: Medicine (Baltimore)
Nathan A Bihlmeyer, Jennifer A Brody, Albert Vernon Smith, Helen R Warren, Honghuang Lin, Aaron Isaacs, Ching-Ti Liu, Jonathan Marten, Farid Radmanesh, Leanne M Hall, Niels Grarup, Hao Mei, Martina Müller-Nurasyid, Jennifer E Huffman, Niek Verweij, Xiuqing Guo, Jie Yao, Ruifang Li-Gao, Marten van den Berg, Stefan Weiss, Bram P Prins, Jessica van Setten, Jeffrey Haessler, Leo-Pekka Lyytikäinen, Man Li, Alvaro Alonso, Elsayed Z Soliman, Joshua C Bis, Tom Austin, Yii-Der Ida Chen, Bruce M Psaty, Tamara B Harrris, Lenore J Launer, Sandosh Padmanabhan, Anna Dominiczak, Paul L Huang, Zhijun Xie, Patrick T Ellinor, Jan A Kors, Archie Campbell, Alison D Murray, Christopher P Nelson, Martin D Tobin, Jette Bork-Jensen, Torben Hansen, Oluf Pedersen, Allan Linneberg, Moritz F Sinner, Annette Peters, Melanie Waldenberger, Thomas Meitinger, Siegfried Perz, Ivana Kolcic, Igor Rudan, Rudolf A de Boer, Peter van der Meer, Henry J Lin, Kent D Taylor, Renée de Mutsert, Stella Trompet, J Wouter Jukema, Arie C Maan, Bruno H C Stricker, Fernando Rivadeneira, André Uitterlinden, Uwe Völker, Georg Homuth, Henry Völzke, Stephan B Felix, Massimo Mangino, Timothy D Spector, Michiel L Bots, Marco Perez, Olli T Raitakari, Mika Kähönen, Nina Mononen, Vilmundur Gudnason, Patricia B Munroe, Steven A Lubitz, Cornelia M van Duijn, Christopher H Newton-Cheh, Caroline Hayward, Jonathan Rosand, Nilesh J Samani, Jørgen K Kanters, James G Wilson, Stefan Kääb, Ozren Polasek, Pim van der Harst, Susan R Heckbert, Jerome I Rotter, Dennis O Mook-Kanamori, Mark Eijgelsheim, Marcus Dörr, Yalda Jamshidi, Folkert W Asselbergs, Charles Kooperberg, Terho Lehtimäki, Dan E Arking, Nona Sotoodehnia
BACKGROUND: QT interval, measured through a standard ECG, captures the time it takes for the cardiac ventricles to depolarize and repolarize. JT interval is the component of the QT interval that reflects ventricular repolarization alone. Prolonged QT interval has been linked to higher risk of sudden cardiac arrest. METHODS AND RESULTS: We performed an ExomeChip-wide analysis for both QT and JT intervals, including 209 449 variants, both common and rare, in 17 341 genes from the Illumina Infinium HumanExome BeadChip...
January 2018: Circulation. Genomic and precision medicine
Yankun Yu, Feng Liu, Liuming He, Seeram Ramakrishna, Monica Zheng, Lei Bu, Ying Xu
Co-administration of sofosbuvir, an anti-hepatitis C virus medication, and antiarrhythmic amiodarone causes symptomatic severe bradycardia in patients and animal models. However, in a few in vitro studies, the combination of sofosbuvir and amiodarone resulted in tachycardiac effects in human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs). This discrepancy may be attributable to the use of immature hiPSC-CMs in the in vitro studies. To address this, we evaluated the ability of our in-house hiPSC-CMs to assess the interactions between sofosbuvir and amiodarone in vitro...
May 30, 2018: Assay and Drug Development Technologies
Roland Veress, Dóra Baranyai, Bence Hegyi, Kornél Kistamás, Csaba Dienes, János Magyar, Tamás Bányász, Péter P Nánási, Norbert Szentandrássy, Balázs Horváth
The role of TRPM4 channels has been frequently tested using their inhibitor 9-phenanthrol in various cardiac preparations, however, the selectivity of the compound is uncertain. Therefore, in the present study the concentration-dependent effects of 9-phenanthrol on major ionic currents were studied in canine isolated ventricular cells using whole-cell configuration of the patch-clamp technique and 10 mM BAPTA-containing pipette solution in order to prevent the Ca2+-dependent activation of TRPM4 channels. Transient outward, rapid delayed rectifier and inward rectifier K+ currents were suppressed by 10 and 30 µM 9-phenanthrol with the blocking potency for IK1<IKr<Ito1 and partial reversibility...
May 28, 2018: Canadian Journal of Physiology and Pharmacology
J L Isaksen, C Graff, C Ellervik, J S Jensen, P Rossing, J K Kanters, M T Jensen
AIMS: To investigate depolarization and repolarization durations in people with Type 1 diabetes, including the relationship to age. METHODS: 855 persons with Type 1 diabetes without known heart disease were included and matched with 1710 participants from a general population study. Clinical examinations, questionnaires and biochemistry were assessed. A 10-second 12-lead ECG was performed and analysed digitally. RESULTS: QTc was longer in people with Type 1 diabetes compared to controls (414±16 vs...
May 23, 2018: Diabetic Medicine: a Journal of the British Diabetic Association
Fabio M Leonelli, Giuseppe Bagliani, Roberto De Ponti, Luigi Padeletti
From the atrioventricular node, electrical activation is propagated to both ventricles by a system of specialized conducting fibers, His Purkinje System (HPS), guaranteeing a fast, synchronous depolarization of both ventricles. From the predivisional common stem, a right and left branch separate, subdividing further in a fairly predictable fashion. Synchronous ventricular activation results in a QRS with specific characteristics and duration of less than 110 milliseconds. Block or delay in any part of the HPS changes the electrocardiographic (ECG) morphology...
June 2018: Cardiac Electrophysiology Clinics
Jana Svehlikova, Michal Teplan, Milan Tysler
The inverse problem of electrocardiography for localization of a premature ventricular contraction (PVC) origin was solved and compared for three types of the equivalent cardiac electrical generator: transmembrane voltages, epicardial potentials, and dipoles. Instead of regularization methods usually used for the ill-posed inverse problems an assumption of a single point source representative of the heart generator was applied to the solution as a geometrical constraint. Body surface potential maps were simulated from eight modeled origins of the PVC in the heart model...
May 2018: Journal of Electrocardiology
Sinan Degirmenci, Yusuf Olgar, Aysegul Durak, Erkan Tuncay, Belma Turan
Intracellular labile (free) Zn2+ -level ([Zn2+ ]i ) is low and increases markedly under pathophysiological conditions in cardiomyocytes. High [Zn2+ ]i is associated with alterations in excitability and ionic-conductances while exact mechanisms are not clarified yet. Therefore, we examined the elevated-[Zn2+ ]i on some sarcolemmal ionic-mechanisms, which can mediate cardiomyocyte dysfunction. High-[Zn2+ ]i induced significant changes in action potential (AP) parameters, including depolarization in resting membrane-potential and prolongations in AP-repolarizing phases...
July 2018: Journal of Trace Elements in Medicine and Biology
Cory M Tschabrunn, Haris M Haqqani, Pasquale Santangeli, Erica S Zado, Francis E Marchlinski
OBJECTIVES: The purpose of this study was to evaluate the relationship between electrocardiogram (ECG) QRS fragmentation (fQRS) and right ventricular (RV) endocardial (ENDO) and epicardial (EPI) electroanatomic substrate abnormalities in patients with arrhythmogenic right ventricular cardiomyopathy (ARVC). BACKGROUND: fQRS is frequently observed in patients with ARVC and reflects delayed conduction due to RV fibrosis. METHODS: A total of 30 consecutive patients met the task force criteria for ARVC (19 men, mean age 41...
July 2017: JACC. Clinical Electrophysiology
Ahmed Badr, El-Sabry Abu-Amra, Mohamed Farag El-Sayed, Matti Vornanen
Exercise, capture and handling stress in fishes can elevate extracellular K+ concentration ([K+ ]o ) with potential impact on heart function. Therefore, effects of [K+ ]o on excitability of ventricular myocytes of winter-acclimatized roach (Rutilus rutilus) (4{plus minus}0.5{degree sign}C) were examined at different temperatures and pacing rates. Frequencies corresponding to in vivo heart rates at 4{degree sign}C (0.37Hz), 14{degree sign}C (1.16Hz) and 24{degree sign}C (1.96Hz) had no effect on excitability of myocytes...
May 2, 2018: American Journal of Physiology. Regulatory, Integrative and Comparative Physiology
Chris Giordano, Jordan Miller, Ilan Keidan
Percussion pacing involves using one's fist to repeatedly strike a patient's left sternal border in a rhythmic manner. The resulting increase in ventricular pressure can trigger myocardial depolarization and subsequent contraction. We describe the successful treatment of acute preoperative symptomatic sinus bradycardia with percussion pacing in a 63-year-old patient scheduled for placement of a gastric feeding tube after trauma involving spinal cord injury. Although no longer included in current advanced cardiovascular life support guidelines, percussion pacing may be a suitable alternative to chest compressions in multitrauma cases where the force of compressions could cause further complications...
May 1, 2018: A&A practice
Takamitsu Tanaka, Masao Saotome, Hideki Katoh, Terumori Satoh, Prottoy Hasan, Hayato Ohtani, Hiroshi Satoh, Hideharu Hayashi, Yuichiro Maekawa
Accumulating evidence has revealed pivotal roles of glycogen synthase kinase-3β (GSK3β) inactivation on cardiac protection. Because the precise mechanisms of cardiac protection against ischemia/reperfusion (I/R) injury by GSK3β-inactivation remain elusive, we investigated the relationship between GSK3β-mediated mitochondrial hexokinase II (mitoHK-II; a downstream target of GSK3β) dissociation and mitochondrial permeability transition pore (mPTP) opening. In Langendorff-perfused hearts, GSK3β inactivation by SB216763 improved the left ventricular-developed pressure and retained mitoHK-II binding after I/R...
April 18, 2018: Journal of Physiological Sciences: JPS
J R Visker, D P Ferguson
Growth restriction caused by postnatal undernutrition increases risk for cardiovascular disease in adulthood with the potential to induce arrhythmogenesis. Thus, the purpose was to determine if undernutrition during development produced arrhythmias at rest and when stressed with dobutamine in adulthood. Mouse dams were fed (CON: 20% protein), or low-protein (LP: 8%) diet before mating. A cross-fostering model was used where pups nursed by dams fed LP diet in early [EUN; postnatal day (PN) 1-10], late (LUN; PN11-21) and whole (PUN; 1-21) phases of postnatal life...
April 12, 2018: Journal of Developmental Origins of Health and Disease
Haitham Badran, Rania Samir, Mohamed Amin
Background: Premature ventricular beats (PVBs) are early depolarization of the myocardium originating in the ventricle. In case of very frequent PVBs, patients are severely symptomatic with impaired quality of life and are at risk of pre-syncope, syncope, heart failure, and sudden cardiac death particularly in the presence of structural heart disease. Ventricular outflow tracts are the most common sites of origin of idiopathic PVBs especially in patients without structural heart disease...
December 2017: The Egyptian heart journal: (EHJ): official bulletin of the Egyptian Society of Cardiology
Joseph Y Cheung, JuFang Wang, Xue-Qian Zhang, Jianliang Song, John M Davidyock, Fabian Jana Prado, Santhanam Shanmughapriya, Alison M Worth, Muniswamy Madesh, Annick Judenherc-Haouzi, Philippe Haouzi
We have previously demonstrated that methylene blue (MB) counteracts the effects of hydrogen sulfide (H2 S) cardiotoxicity by improving cardiomyocyte contractility and intracellular Ca2+ homeostasis disrupted by H2 S poisoning. In vivo, MB restores cardiac contractility severely depressed by sulfide and protects against arrhythmias, ranging from bundle branch block to ventricular tachycardia or fibrillation. To dissect the cellular mechanisms by which MB reduces arrhythmogenesis and improves bioenergetics in myocytes intoxicated with H2 S, we evaluated the effects of H2 S on resting membrane potential (Em ), action potential (AP), Na+ /Ca2+ exchange current (INaCa ), depolarization-activated K+ currents and ATP levels in adult mouse cardiac myocytes and determined whether MB could counteract the toxic effects of H2 S on myocyte electrophysiology and ATP...
March 30, 2018: Cardiovascular Toxicology
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