Beat Rate Variability Research Articles

Drug Interactions between Traditional Chinese Medicines and Cardiovascular Drugs.

Cardiovascular disease (CVD) is one of the leading causes of death worldwide, and its internal medicine treatments are mostly single/few-target chemical drugs. Long-term use of cardiovascular drugs for complex chronic diseases may lead to serious adverse drug reactions. Traditional Chinese medicine (TCM) has been used to treat heart diseases for thousands of years, helping to ease symptoms and prolong patients' lifespan in ancient China. TCM has the pharmacological characteristics of being multi-component, multi-target and multi-pathway, and the combined application of TCM and western medicine can be an alternative treatment for chronic and intractable diseases with high safety levels. This article reviewed the interactions and synergistic effect of TCM and cardiovascular drugs. In the treatment of arrhythmia, TCM combined with western medicine can more effectively regulate patients' cardiac electrophysiological characteristics, reduce the onsets of premature beat and heart rate variability, lower the levels of QT interval dispersion and serum inflammatory factors, alleviate clinical symptoms and TCM syndromes, and improve cardiac function with good safety levels. In the treatment of hypertension, integrative medicine can more steadily reduce blood pressure and levels of serum inflammatory factors and improve hemodynamic indexes and exercise tolerance, and it has high safety levels, especially for pregnant women. As for coronary heart disease, the combination of TCM and antiplatelet drugs may promote the absorption of each other. However, the interaction risk of pharmacokinetic mechanism between them is low at the dose of efficacy. Integrative medicine can reduce the level of N-terminal pro-brain natriuretic peptide, delay cardiac remodeling and improve heart function and quality of life for patients with heart failure with high safety levels.

Autonomous detection of myocarditis based on the fusion of improved quantum genetic algorithm and adaptive differential evolution optimization back propagation neural network.

Myocarditis is cardiac damage caused by a viral infection. Its result often leads to a variety of arrhythmias. However, rapid and reliable identification of myocarditis has a great impact on early diagnosis, expedited treatment, and improved patient survival rates. Therefore, a novel strategy for the autonomous detection of myocarditis is suggested in this work. First, the improved quantum genetic algorithm (IQGA) is proposed to extract the optimal features of ECG beat and heart rate variability (HRV) from raw ECG signals. Second, the backpropagation neural network (BPNN) is optimized using the adaptive differential evolution (ADE) algorithm to classify various ECG signal types with high accuracy. This study examines analogies among five different ECG signal types: normal, abnormal, myocarditis, myocardial infarction (MI), and prior myocardial infarction (PMI). Additionally, the study uses binary and multiclass classification to group myocarditis with other cardiovascular disorders in order to assess how well the algorithm performs in categorization. The experimental results demonstrate that the combination of IQGA and ADE-BPNN can effectively increase the precision and accuracy of myocarditis autonomous diagnosis. In addition, HRV assesses the method's robustness, and the classification tool can detect viruses in myocarditis patients one week before symptoms worsen. The model can be utilized in intensive care units or wearable monitoring devices and has strong performance in the detection of myocarditis.

Cellular Biomechanic Impairment in Cardiomyocytes Carrying the Progeria Mutation: An Atomic Force Microscopy Investigation.

Given the clinical effect of progeria syndrome, understanding the cell mechanical behavior of this pathology could benefit the patient's treatment. Progeria patients show a point mutation in the lamin A/C gene (LMNA), which could change the cell's biomechanical properties. This paper reports a mechano-dynamic analysis of a progeria mutation (c.1824 C > T, p.Gly608Gly) in neonatal rat ventricular myocytes (NRVMs) using cell indentation by atomic force microscopy to measure alterations in beating force, frequency, and contractile amplitude of selected cells within cell clusters. Furthermore, we examined the beating rate variability using a time-domain method that produces a Poincaré plot because beat-to-beat changes can shed light on the causes of arrhythmias. Our data have been further related to our cell phenotype findings, using immunofluorescence and calcium transient analysis, showing that mutant NRVMs display changes in both beating force and frequency. These changes were associated with a decreased gap junction localization (Connexin 43) in the mutant NRVMs even in the presence of a stable cytoskeletal structure (microtubules and actin filaments) when compared with controls (wild type and non-treated cells). These data emphasize the kindred between nucleoskeleton (LMNA), cytoskeleton, and the sarcolemmal structures in NRVM with the progeria Gly608Gly mutation, prompting future mechanistic and therapeutic investigations.

Active force generation contributes to the complexity of spontaneous activity and to the response to stretch of murine cardiomyocyte cultures.

Cardiomyocyte cultures exhibit spontaneous electrical and contractile activity, as in a natural cardiac pacemaker. In such preparations, beat rate variability exhibits features similar to those of heart rate variability in vivo. Mechanical deformations and forces feed back on the electrical properties of cardiomyocytes, but it is not fully elucidated how this mechano‐electrical interplay affects beating variability in such preparations. Using stretchable microelectrode arrays, we assessed the effects of the myosin inhibitor blebbistatin and the non‐selective stretch‐activated channel blocker streptomycin on beating variability and on the response of neonatal or fetal murine ventricular cell cultures against deformation. Spontaneous electrical activity was recorded without stretch and upon predefined deformation protocols (5% uniaxial and 2% equibiaxial strain, applied repeatedly for 1 min every 3 min). Without stretch, spontaneous activity originated from the edge of the preparations, and its site of origin switched frequently in a complex manner across the cultures. Blebbistatin did not change mean beat rate, but it decreased the spatial complexity of spontaneous activity. In contrast, streptomycin did not exert any manifest effects. During the deformation protocols, beat rate increased transiently upon stretch but, paradoxically, also upon release. Blebbistatin attenuated the response to stretch, whereas this response was not affected by streptomycin. Therefore, our data support the notion that in a spontaneously firing network of cardiomyocytes, active force generation, rather than stretch‐activated channels, is involved mechanistically in the complexity of the spatiotemporal patterns of spontaneous activity and in the stretch‐induced acceleration of beating. Key points Monolayer cultures of cardiac cells exhibit spontaneous electrical and contractile activity, as in a natural cardiac pacemaker. Beating variability in these preparations recapitulates the power‐law behaviour of heart rate variability in vivo. However, the effects of mechano‐electrical feedback on beating variability are not yet fully understood.Using stretchable microelectrode arrays, we examined the effects of the contraction uncoupler blebbistatin and the non‐specific stretch‐activated channel blocker streptomycin on beating variability and on stretch‐induced changes of beat rate.Without stretch, blebbistatin decreased the spatial complexity of beating variability, whereas streptomycin had no effects.Both stretch and release increased beat rate transiently; blebbistatin attenuated the increase of beat rate upon stretch, whereas streptomycin had no effects.Active force generation contributes to the complexity of spatiotemporal patterns of beating variability and to the increase of beat rate upon mechanical deformation. Our study contributes to the understanding of how mechano‐electrical feedback influences heart rate variability.

Effects of blebbistatin and streptomycin on beat rate variability and mechano-electric feedback in spontaneously active cardiomyocyte cultures

Monolayer cultures of cardiac cells exhibit spontaneous electrical and contractile activity and represent an in vitro model of a natural cardiac pacemaker. In such preparations, it was shown previously that beat rate variability (BRV) exhibits features similar to those of heart rate variability in vivo. However, tissue deformation and mechanical forces feedback on the electrical properties of cardiomyocytes (mechano-electrical feedback) e.g., through stretch-activated channels (SACs), and it is not known how mechano-electrical feedback affects BRV in such preparations. Our objective was to assess the contribution of active force generation and SACs on BRV and on the response of neonatal or fetal murine ventricular cell cultures to mechanical deformation. Monolayer cultures were grown on stretchable microelectrode arrays. Spontaneous electrical activity was recorded without deformation and upon predefined deformation protocols (5% uniaxial and 2% biaxial strain, applied repeatedly for 1 min every 3 min), before and after the application of the myosin inhibitor blebbistatin (10 μmol/L) or the SAC blocker streptomycin (20 μmol/L). Without deformation, spontaneous activity originated from the edge of the preparations and the site of origin switched frequently in a complex manner. Blebbistatin did not change mean beat rate, but it decreased the spatial complexity of beating variability. In contrast, streptomycin did not exert any manifest effects on spontaneous activity. During the deformation protocols, beat rate transiently increased upon stretch, but paradoxically also upon release. Blebbistatin attenuated the response to stretch, while this response was not manifestly affected by streptomycin. These results indicate that any change of shape transiently increases beat rate. Importantly, active force generation, rather than SACs, appears to be mechanistically involved in this response as well as in the complexity of spatiotemporal BRV patterns. Our study thus contributes to understand how mechano-electric feedback may influence heart rate variability.

The influence of light on the beat rate variability of murine embryonic stem cell derived cardiomyocytes

BackgroundThe human heart rhythm can be quantified by analyzing the heart rate variability (HRV). A major influencing factor of the HRV is the circadian rhythm. The ocular light and the hormone melatonin play decisive roles in the circadian rhythm.The beat rate variability (BRV) is considered to be the in vitro equivalent of the HRV. Previous studies have demonstrated the influence of melatonin on cardiomyocytes. Also, the influence of light on cardiomyocytes has been described before. Nevertheless, the effect of light on the BRV of cardiomyocytes has not yet been examined. Material and methodsThe BRV of spontaneously beating cardiomyocytes was measured with microelectrode arrays over a time period of 30 min. The experiments were either performed with light exposure (with and without an infrared filter) or in complete darkness. ResultsThe BRV was higher and the beating frequency was lower when the cardiomyocytes were exposed to the full spectrum of light, compared to the measurements in darkness as well as to the measurements with an infrared filter. In contrast, the differences of BRV between the measurements in darkness and the measurements with an infrared filter were not as distinct. ConclusionsThis is the first study demonstrating the influence of light on the beating rhythm of heart tissue in vitro. The results indicate that especially the infrared spectrum of light alters the BRV. These findings could be of interest for clinical applications such as the field of optical pacing as well as in neonatal patient care.

Beating Rate Variability of Isolated Mammal Sinoatrial Node Tissue: Insight Into Its Contribution to Heart Rate Variability.

BackgroundBecause of the complexity of the interaction between the internal pacemaker mechanisms, cell interconnected signals, and interaction with other body systems, study of the role of individual systems must be performed under in vivo and in situ conditions. The in situ approach is valuable when exploring the mechanisms that govern the beating rate and rhythm of the sinoatrial node (SAN), the heart’s primary pacemaker. SAN beating rate changes on a beat-to-beat basis. However, to date, there are no standard methods and tools for beating rate variability (BRV) analysis from electrograms (EGMs) collected from different mammals, and there is no centralized public database with such recordings.MethodsWe used EGM recordings obtained from control SAN tissues of rabbits (n = 9) and mice (n = 30) and from mouse SAN tissues (n = 6) that were exposed to drug intervention. The data were harnessed to develop a beat detector to derive the beat-to-beat interval time series from EGM recordings. We adapted BRV measures from heart rate variability and reported their range for rabbit and mouse.ResultsThe beat detector algorithm performed with 99% accuracy, sensitivity, and positive predictive value on the test (mouse) and validation (rabbit and mouse) sets. Differences in the frequency band cutoff were found between BRV of SAN tissue vs. heart rate variability (HRV) of in vivo recordings. A significant reduction in power spectrum density existed in the high frequency band, and a relative increase was seen in the low and very low frequency bands. In isolated SAN, the larger animal had a slower beating rate but with lower BRV, which contrasted the phenomena reported for in vivo analysis. Thus, the non-linear inverse relationship between the average HR and HRV is not maintained under in situ conditions. The beat detector, BRV measures, and databases were contributed to the open-source PhysioZoo software (available at: https://physiozoo.com/).ConclusionOur approach will enable standardization and reproducibility of BRV analysis in mammals. Different trends were found between beating rate and BRV or HRV in isolated SAN tissue vs. recordings collected under in vivo conditions, respectively, implying a complex interaction between the SAN and the autonomic nervous system in determining HRV in vivo.

The influence of melatonin on the heart rhythm – An in vitro simulation with murine embryonic stem cell derived cardiomyocytes

BackgroundIn healthy individuals, a major factor influencing the heart rate variability (HRV) is the circadian rhythm. The role of melatonin as an essential component of the circadian rhythm in the adult human organism and the beneficial effects of a treatment with melatonin during the fetal period is well described. Toxic effects of melatonin are discussed less frequently.Since pharmacological studies cannot be carried out on pregnant women, the establishment of an equivalent in vitro model is important. We therefore tested whether melatonin can influence the beat rate variability (BRV) of spontaneously beating cardiomyocytes derived from murine embryonic stem cells (mESCs) and whether melatonin exhibits toxic effects in this in vitro model. MethodsMicroelectrode Arrays recorded extracellular field potentials of spontaneously beating cardiomyocytes. Melatonin was applied in a concentration range from 10−11 M to 10–5 M. The analysis of the BRV focused on time domain methods. ResultsIn line with clinical observations, melatonin decreased the beating frequency and increased the BRV. The effect of melatonin up to a concentration of 10−6 M was reversible, whereas the application of higher concentrations induced an irreversible effect. ConclusionThe study underlines the potential of this in vitro model to help explore the development of circadian rhythms and their modulation by melatonin in the embryonic phase. The results imply that melatonin influences the heart rhythm as early as during the embryonic heart development. Furthermore, the results indicate a potentially toxic effect of melatonin that has not been described in detail before.

Intrinsic Sinoatrial Node Dysfunction Impairs Autonomic Regulation of Heart Rate Variability in Hypertensive Heart Disease

Vagal control of the sinoatrial node (SAN) is a major mechanism that regulates beat-to-beat heart rate variability (HRV) at rest. Classically, reduced HRV in the setting of hypertensive heart disease and heart failure has been attributed to chronically elevated sympathetic and reduced vagal regulation of heart rate. However, both of these conditions are also associated with intrinsic SAN dysfunction which may change the gain and dynamic response of the SAN to autonomic stimulation. The relationship between autonomic nerve activity and the responsiveness of SAN myocytes to descending neural signals in hypertension remain unclear. Here, we investigated how intrinsic SAN dysfunction impacts autonomic regulation of HRV in a mouse model of angiotensin II (AngII) mediated hypertensive heart disease. Mice infused with AngII via mini-osmotic pumps (2.5mg/kg/day for 3 weeks) had reduced HRV and increased adrenergic tone indicated by elevated renal sympathetic nerve activity and circulating catecholamine levels. Interestingly, AngII infused mice had no change in vagal nerve activity compared to saline treated controls. Electrograms recorded from isolated atrial preparations devoid of neural input, as well as isolated SAN myocytes assessed through patch clamp electrophysiology, demonstrated increased beating rate variability and reduced responsiveness to both the β-adrenergic agonist isoproterenol and the muscarinic agonist carbachol. Together, these data suggest that the SAN is a major contributor to the loss of regular HRV in hypertensive heart disease due to desensitization of descending neural signals. Our data suggests that elevated sympathetic tone, in conjunction with reduced responsiveness of the SAN to parasympathetic agonists, are responsible for diminished HRV in the setting of hypertensive heart disease. Thus, the interpretation of HRV as a pure measure of cardiac autonomic tone may be inappropriate in the setting of diseases with concurrent SAN dysfunction.

Altered microtubule structure, hemichannel localization and beating activity in cardiomyocytes expressing pathologic nuclear lamin A/C

Given the clinical effect of laminopathies, understanding lamin mechanical properties will benefit the treatment of heart failure. Here we report a mechano-dynamic study of LMNA mutations in neonatal rat ventricular myocytes (NRVM) using single cell spectroscopy with Atomic Force Microscopy (AFM) and measured changes in beating force, frequency and contractile amplitude of selected mutant-expressing cells within cell clusters. Furthermore, since beat-to-beat variations can provide clues on the origin of arrhythmias, we analyzed the beating rate variability using a time-domain method which provides a Poincaré plot. Data were further correlated to cell phenotypes. Immunofluorescence and calcium imaging analysis showed that mutant lamin changed NRVMs beating force and frequency. Additionally, we noted an altered microtubule network organization with shorter filament length, and defective hemichannel membrane localization (Connexin 43). These data highlight the interconnection between nucleoskeleton, cytoskeleton and sarcolemmal structures, and the transcellular consequences of mutant lamin protein in the pathogenesis of the cardiac laminopathies.

Adult human cardiac stem cell supplementation effectively increases contractile function and maturation in human engineered cardiac tissues

BackgroundDelivery of stem cells to the failing heart is a promising therapeutic strategy. However, the improvement in cardiac function in animal studies has not fully translated to humans. To help bridge the gap between species, we investigated the effects of adult human cardiac stem cells (hCSCs) on contractile function of human engineered cardiac tissues (hECTs) as a species-specific model of the human myocardium.MethodsHuman induced pluripotent stem cell-derived cardiomyoctes (hCMs) were mixed with Collagen/Matrigel to fabricate control hECTs, with an experimental group of hCSC-supplemented hECT fabricated using a 9:1 ratio of hCM to hCSC. Functional testing was performed starting on culture day 6, under spontaneous conditions and also during electrical pacing from 0.25 to 1.0 Hz, measurements repeated at days 8 and 10. hECTs were then frozen and processed for gene analysis using a Nanostring assay with a cardiac targeted custom panel.ResultsThe hCSC-supplemented hECTs displayed a twofold higher developed force vs. hCM-only controls by day 6, with approximately threefold higher developed stress and maximum rates of contraction and relaxation during pacing at 0.75 Hz. The spontaneous beat rate characteristics were similar between groups, and hCSC supplementation did not adversely impact beat rate variability. The increased contractility persisted through days 8 and 10, albeit with some decrease in the magnitude of the difference of the force by day 10, but with developed stress still significantly higher in hCSC-supplemented hECT; these findings were confirmed with multiple hCSC and hCM cell lines. The force-frequency relationship, while negative for both, control (− 0.687 Hz− 1; p = 0.013 vs. zero) and hCSC-supplemented (− 0.233 Hz− 1;p = 0.067 vs. zero) hECTs, showed a significant rectification in the regression slope in hCSC-supplemented hECT (p = 0.011 vs. control). Targeted gene exploration (59 genes) identified a total of 14 differentially expressed genes, with increases in the ratios of MYH7/MHY6, MYL2/MYL7, and TNNI3/TNNI1 in hCSC-supplemented hECT versus controls.ConclusionsFor the first time, hCSC supplementation was shown to significantly improve human cardiac tissue contractility in vitro, without evidence of proarrhythmic effects, and was associated with increased expression of markers of cardiac maturation. These findings provide new insights about adult cardiac stem cells as contributors to functional improvement of human myocardium.

The Effect of Antiarrhythmic Drugs on the Beat Rate Variability of Human Embryonic and Human Induced Pluripotent Stem Cell Derived Cardiomyocytes

Embryonic stem cell (ESC) derived tissue is a promising tool to be used in different clinical, preclinical and also scientific settings, for example as in vivo biological pacemaker, preclinical drug safety screening tool or ultimately as part of a cell replacement therapy. However, before ESC derived tissue can be used routinely for these purposes in humans, further studies are needed. In this context, the aims of the present study were to examine the effect of antiarrhythmic drugs on human ESC (hESC) und human induced pluripotent stem cell (hiPSC) derived cardiomyocytes by analyzing the beat rate variability (BRV), which can be considered as the in vitro equivalent of the heart rate variability (HRV) in vivo. Short-term recordings of extracellular field potentials of spontaneously beating cardiomyocytes derived from hESCs and hiPSCs were made using Microelectrode Arrays (MEA). The effect of Flecainide, Ivabradine and Metoprolol was tested. The offline analysis of the BRV was mainly focused on time domain methods. Additionally a non-linear analysis method was used. The evaluation of the Poincaré-Plots of the measurements without pharmacological intervention revealed that the vast majority of the scatter plots have a similar, ellipsoid shape. Flecainide and Ivabradine influenced BRV parameters significantly, whereas Metoprolol did not alter the BRV markedly. We detected remarkable similarities between the BRV of hESC and hiPSC derived cardiomyocytes in vitro and the HRV in vivo. The effect of antiarrhythmic drugs on spontaneously beating cardiomyocytes derived from hESC and hiPSC was generally consistent with clinical experiences and also with our previous study based on murine ESC derived cardiomyocytes. In conclusion, our study points out the great potential of hESC and hiPSC derived tissue to be used routinely for many different applications in medicine and science.

Design of RZF antenna for ECG monitoring using IoT

The application of smart health by using the Internet of Things as a medium between the transmissions of the Electro-cardio gram signal acquired from the human body to the care takers. We implemented a ECG monitoring system. Here place the electrodes on the surface of the patient’s body by time to time. These signals are transferred to the cloud by using the transmission modules which has been implemented using Rectangular Zig Fractional (RZF) antenna. The design and implementation of RZF antenna with triple-band Doppler system for contactless heartbeat monitoring is proposed. It consists of a slotted rectangular shaped ground plane and a modified radiating patch with four-folded arms that integrates microwave transceivers and power amplifier, which occupies a compact size of 12 × 18 mm2 to be easily embedded within a portable device as an internal antenna. The antenna shows omnidirectional radiation pattern with the gain value of 8.4 dBi, 9.5 dBi and 13.5dBi resonates at 2.4/3.5/5.8 GHz with the stability factor greater than 1 and the 50 Ω impedance matching with Smith Chart is achieved. The RZF Antenna system is satisfactory for monitoring heart beat and heart beat rate variability vital signs. The antenna is tested at 2.4/3.5/5.8 GHz frequency for transmitted power levels ranges 0 dBm and-5 dBm. With Doppler system, the heart beat rate and heart rate variability are acquired from the reflected signals and compared to the simultaneous ECG signals and the information of HR and HRV is then transferred to the receiver or doctor end by means of IoT server.

Electrophysiological abnormalities in induced pluripotent stem cell-derived cardiomyocytes generated from Duchenne muscular dystrophy patients.

Duchenne muscular dystrophy (DMD) is an X‐linked progressive muscle degenerative disease, caused by mutations in the dystrophin gene and resulting in death because of respiratory or cardiac failure. To investigate the cardiac cellular manifestation of DMD, we generated induced pluripotent stem cells (iPSCs) and iPSC‐derived cardiomyocytes (iPSC‐CMs) from two DMD patients: a male and female manifesting heterozygous carrier. Dystrophin mRNA and protein expression were analysed by qRT‐PCR, RNAseq, Western blot and immunofluorescence staining. For comprehensive electrophysiological analysis, current and voltage clamp were used to record transmembrane action potentials and ion currents, respectively. Microelectrode array was used to record extracellular electrograms. X‐inactive specific transcript (XIST) and dystrophin expression analyses revealed that female iPSCs underwent X chromosome reactivation (XCR) or erosion of X chromosome inactivation, which was maintained in female iPSC‐CMs displaying mixed X chromosome expression of wild type (WT) and mutated alleles. Both DMD female and male iPSC‐CMs presented low spontaneous firing rate, arrhythmias and prolonged action potential duration. DMD female iPSC‐CMs displayed increased beat rate variability (BRV). DMD male iPSC‐CMs manifested decreased I f density, and DMD female and male iPSC‐CMs showed increased I Ca,L density. Our findings demonstrate cellular mechanisms underlying electrophysiological abnormalities and cardiac arrhythmias in DMD.

Disruption of neonatal cardiomyocyte physiology following exposure to bisphenol-a

Bisphenol chemicals are commonly used in the manufacturing of polycarbonate plastics, polyvinyl chloride plastics, resins, and thermal printing applications. Humans are inadvertently exposed to bisphenols through contact with consumer products and/or medical devices. Recent reports have shown a link between bisphenol-a (BPA) exposure and adverse cardiovascular outcomes; although these studies have been limited to adult subjects and models. Since cardiac physiology differs significantly between the developing and adult heart, we aimed to assess the impact of BPA exposure on cardiac function, using a neonatal cardiomyocyte model. Neonatal rat ventricular myocytes were monitored to assess cell viability, spontaneous beating rate, beat rate variability, and calcium-handling parameters in the presence of control or bisphenol-supplemented media. A range of doses were tested to mimic environmental exposure (10−9–10−8M), maximum clinical exposure (10−5M), and supraphysiological exposure levels (10−4M). Acute BPA exposure altered cardiomyocyte functionality, resulting in a slowed spontaneous beating rate and increased beat rate variability. BPA exposure also impaired intracellular calcium handling, resulting in diminished calcium transient amplitudes, prolonged calcium transient upstroke and duration time. Alterations in calcium handling also increased the propensity for alternans and skipped beats. Notably, the effect of BPA-treatment on calcium handling was partially reversible. Our data suggest that acute BPA exposure could precipitate secondary adverse effects on contractile performance and/or electrical alternans, both of which are dependent on intracellular calcium homeostasis.

CYP2J2 inhibition: the arcane mechanism of dronedarone‐induced proarrhythmia

BackgroundLike other Class III antiarrhythmic, dronedarone and amiodarone are potent human Ether‐à‐go‐go‐Related Gene (hERG) channel inhibitors.1–2 Although structurally and pharmacologically similar, dronedarone is known to worsen cardiac proarrhythmia3 and increase mortality in patients with permanent atrial fibrillation4 while amiodarone does not. Previously we demonstrated dronedarone is a more potent inhibitor of recombinant human cytochrome P4502J2 (CYP2J2)4 compared to amiodarone and yields negative perturbation of eicosatrienoic acid homeostasis5.ObjectivesWe aimed to investigate and compare the in vitro proarrhythmic potential of dronedarone and amiodarone and CYP2J2 inhibition in a cellular model.MethodsWe first measured the expression of CYP2J2 in human induced pluripotent stem cell derived cardiomyocytes (hiPSC‐CMs) using quantitative PCR. The extent of CYP2J2 inhibition in hiPSC‐CMs was measured using astemizole as a probe substrate. The electrophysiological changes in terms of field potential duration (FPD) and beat rate variability (BRV) were measured using multielectrode array.ResultsCYP2J2 is abundantly expressed in hiPSC‐CMs. Unlike amiodarone, dronedarone potently inhibited CYP2J2 activity (97%) at 1 μM. Both dronedarone and amiodarone yielded concentration‐dependent increase in FPD. Dronedarone showed 17‐fold and 2‐fold higher BRV compared to control and amiodarone at unbound plasma drug concentrations. Higher extent of CYP2J2 inhibition correlates with higher BRV.ConclusionDronedarone‐induced BRV corroborates its clinical proarrhythmia. For the first time, our study illuminates the currently arcane contribution of CYP2J2 inhibition to drug‐induced proarrhythmia.Support or Funding InformationSingapore Ministry of Education Tier 1 Funding (R‐148‐000‐193‐112) provided to Eric Chun Yong Chan.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Environmental chemicals can disrupt neonatal cardiomyocyte physiology

BackgroundThe ubiquitous nature of plastics has raised concerns pertaining to continuous exposure to plastic polymers and human health risks. Of particular concern is the use of endocrine‐disrupting chemicals in plastic production, including bisphenol A (BPA). Widespread and continuous exposure to BPA can occur through dietary intake, inhalation, dermal and intravenous exposure via consumer products and medical devices. Recent studies have shown a link between BPA exposure and adverse cardiovascular outcomes. This is particularly concerning for vulnerable populations who are at risk of high BPA exposure due to medical treatment, including pediatric patients. Despite significant differences in the cardiac physiology of the developing and adult heart, our current understanding of BPA‐induced cardiac dysfunction has been limited to adult models.ObjectiveCardiac physiology differs significantly between the pediatric and adult heart. We aimed to determine the extent to which BPA exposure contributes to cardiovascular dysfunction, using a neonatal cardiomyocyte model.MethodsNeonatal rat ventricular myocytes (NRVM) were monitored to assess cell viability, spontaneous beating rate, beat rate variability, and calcium‐handling in the presence of control or bisphenol‐supplemented media. A range of environmental and clinically‐relevant exposure levels were tested [10−9 – 10−5M].ResultsAcute BPA exposure (15 – 20 min) altered cardiomyocyte functionality, resulting in a slowed spontaneous beating rate and increased beat rate variability beginning at low concentrations (10−8M BPA). BPA exposure also impaired intracellular calcium handling, resulting in diminished calcium transient amplitudes and prolonged calcium transient duration time, which replicated our previously published studies in isolated‐whole hearts. BPA‐induced changes in calcium handling increased the propensity for calcium transient alternans, beginning at low BPA concentrations (10−9M). The observed alterations in calcium kinetics following BPA exposure were not the result of cytotoxicity or altered cell viability.ConclusionOur studies show that acute BPA chemical exposure can alter neonatal cardiomyocyte physiology. Additional studies are necessary to determine the effects of bisphenol exposure on pediatric heart electrophysiology and mechanical function, as well as the impact of long‐term treatment that more closely mimics clinical exposure.Support or Funding InformationThis publication was supported by the National Institutes of Health (R00ES023477, UL1TR000075), Children's Research Institute and Children's National Heart Institute.

Investigating the cardiac pathology of SCO2-mediated hypertrophic cardiomyopathy using patients induced pluripotent stem cell-derived cardiomyocytes.

Mutations in SCO2 are among the most common causes of COX deficiency, resulting in reduced mitochondrial oxidative ATP production capacity, often leading to hypertrophic cardiomyopathy (HCM). To date, none of the recent pertaining reports provide deep understanding of the SCO2 disease pathophysiology. To investigate the cardiac pathology of the disease, we were the first to generate induced pluripotent stem cell (iPSC)‐derived cardiomyocytes (iPSC‐CMs) from SCO2‐mutated patients. For iPSC generation, we reprogrammed skin fibroblasts from two SCO2 patients and healthy controls. The first patient was a compound heterozygote to the common E140K mutation, and the second was homozygote for the less common G193S mutation. iPSC were differentiated into cardiomyocytes through embryoid body (EB) formation. To test the hypothesis that the SCO2 mutation is associated with mitochondrial abnormalities, and intracellular Ca2+‐overload resulting in functional derangements and arrhythmias, we investigated in SCO2‐mutated iPSC‐CMs (compared to control cardiomyocytes): (i) the ultrastructural changes; (ii) the inotropic responsiveness to β‐adrenergic stimulation, increased [Ca2+]o and angiotensin‐II (AT‐II); and (iii) the Beat Rate Variability (BRV) characteristics. In support of the hypothesis, we found in the mutated iPSC‐CMs major ultrastructural abnormalities and markedly attenuated response to the inotropic interventions and caffeine, as well as delayed afterdepolarizations (DADs) and increased BRV, suggesting impaired SR Ca2+ handling due to attenuated SERCA activity caused by ATP shortage. Our novel results show that iPSC‐CMs are useful for investigating the pathophysiological mechanisms underlying the SCO2 mutation syndrome.

CRISPR correction of the PRKAG2 gene mutation in the patient's induced pluripotent stem cell-derived cardiomyocytes eliminates electrophysiological and structural abnormalities

Mutations in the PRKAG2 gene encoding the γ-subunit of adenosine monophosphate kinase (AMPK) cause hypertrophic cardiomyopathy (HCM) and familial Wolff-Parkinson-White (WPW) syndrome. Patients carrying the R302Q mutation in PRKAG2 present with sinus bradycardia, escape rhythms, ventricular preexcitation, supraventricular tachycardia, and atrioventricular block. This mutation affects AMPK activity and increases glycogen storage in cardiomyocytes. The link between glycogen storage, WPW syndrome, HCM, and arrhythmias remains unknown. The purpose of this study was to investigate the pathological changes caused by the PRKAG2 mutation. We tested the hypothesis that patient's induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs) display clinical aspects of the disease. Using clustered regularly interspaced short palindromic repeats (CRISPR) technology, we corrected the mutation and then generated isogenic iPSC-CMs. Action potentials were recorded from spontaneously firing and paced cardiomyocytes using the patch clamp technique. Using a microelectrode array setup, we recorded electrograms from iPSC-CMs clusters. Transmission electron microscopy was used to detect ultrastructural abnormalities in the mutated iPSC-CMs. PRKAG2-mutated iPSC-CMs exhibited abnormal firing patterns, delayed afterdepolarizations, triggered arrhythmias, and augmented beat rate variability. Importantly, CRISPRcorrection eliminated the electrophysiological abnormalities, the augmented glycogen, storage, and cardiomyocyte hypertrophy. PRKAG2-mutated iPSC-CMs displayed functional and structural abnormalities, which were abolished by correcting the mutation in the patient's iPSCs using CRISPR technology.

Developmental changes in electrophysiological characteristics of human-induced pluripotent stem cell–derived cardiomyocytes

Previous studies proposed that throughout differentiation of human induced Pluripotent Stem Cell-derived cardiomyocytes (iPSC-CMs), only 3 types of action potentials (APs) exist: nodal-, atrial-, and ventricular-like. To investigate whether there are precisely 3 phenotypes or a continuum exists among them, we tested 2 hypotheses: (1) During culture development a cardiac precursor cell is present that-depending on age-can evolve into the 3 phenotypes. (2) The predominant pattern is early prevalence of a nodal phenotype, transient appearance of an atrial phenotype, evolution to a ventricular phenotype, and persistence of transitional phenotypes. To test these hypotheses, we (1) performed fluorescence-activated cell sorting analysis of nodal, atrial, and ventricular markers; (2) recorded APs from 280 7- to 95-day-old iPSC-CMs; and (3) analyzed AP characteristics. The major findings were as follows: (1) fluorescence-activated cell sorting analysis of 30- and 60-day-old cultures showed that an iPSC-CMs population shifts from the nodal to the atrial/ventricular phenotype while including significant transitional populations; (2) the AP population did not consist of 3 phenotypes; (3) culture aging was associated with a shift from nodal to ventricular dominance, with a transient (57-70 days) appearance of the atrial phenotype; and (4) beat rate variability was more prominent in nodal than in ventricular cardiomyocytes, while pacemaker current density increased in older cultures. From the onset of development in culture, the iPSC-CMs population includes nodal, atrial, and ventricular APs and a broad spectrum of transitional phenotypes. The most readily distinguishable phenotype is atrial, which appears only transiently yet dominates at 57-70 days of evolution.