Genetic Determinants of Hereditary Bradyarrhythmias: A Contemporary Review of a Diverse Group of Disorders

Analysis of prescription medication rules of traditional Chinese medicine for bradyarrhythmia treatment based on data mining

BACKGROUND

Multiple studies have revealed that Traditional Chinese Medicine (TCM) prescriptions can provide protective effect on the cardiovascular system, increase the heart rate and relieve the symptoms of patients with bradyarrhythmia. In China, the TCM treatment of bradyarrhythmia is very common, which is also an effective complementary therapy. In order to further understand the application of Chinese medicines in bradyarrhythmia, we analyzed the medication rules of TCM prescriptions for bradyarrhythmia by data mining methods based on previous clinical studies.

METHODS

We searched studies reporting the clinical effect of TCM on bradyarrhythmia in the PubMed and Chinese databases China National Knowledge Infrastructure database, and estimated publication bias by risk of bias tools ROB 2. Descriptive analysis, hierarchical clustering analysis and association rule analysis based on Apriori algorithm were carried out by Microsoft Excel, SPSS Modeler, SPSS Statistics and Rstidio, respectively. Association rules, co-occurrence and clustering among Chinese medicines were found.

RESULTS

A total of 48 studies were included in our study. Among the total 99 kinds of Chinese medicines, 22 high-frequency herbs were included. Four new prescriptions were obtained by hierarchical cluster analysis. 81 association rules were found based on association rule analysis, and a core prescription was intuitively based on the grouping matrix of the top 15 association rules (based on confidence level), of which Guizhi, Zhigancao, Wuweizi, Chuanxiong, Danshen, Danggui, Huangqi, Maidong, Dangshen, Rougui were the most strongly correlated herbs and in the core position.

CONCLUSION

In this study, data mining strategy was applied to explore the TCM prescription for the treatment of bradyarrhythmia, and high-frequency herbs and core prescription were found. The core prescription was in line with the treatment ideas of TCM for bradyarrhythmia, which could intervene the disease from different aspects and adjust the patient's Qi, blood, Yin and Yang, so as to achieve the purpose of treatment.

Italian Cardiological Guidelines (COCIS) for Competitive Sport Eligibility in athletes with heart disease: update 2020

Since 1989, SIC Sport and a FMSI, in partnership with leading Italian Cardiological Scientific Associations (ANCE, ANMCO and SIC) have produced Cardiological Guidelines for Completive Sports Eligibility for athletes with heart disease (COCIS -- 1989, 1995, 2003, 2009 and 2017). The English version of the Italian Cardiological Guidelines for Competitive Sports Eligibility for athletes with heart disease was published in 2013 in this Journal. This publication is an update with respect to the document previously published in English in 2013. It includes the principal innovations that have emerged over recent years, and is divided into five main chapters: arrhythmias, ion channel disorders, congenital heart diseases, acquired valve diseases, cardiomyopathies, myocarditis and pericarditis and ischemic heart disease. Wherever no new data have been introduced with respect to the 2013 publication, please refer to the previous version. This document is intended to complement recent European and American guidelines but an important difference should be noted. The European and American guidelines indicate good practice for people engaging in physical activity at various levels, not only at the competitive level. In contrast, the COCIS guidelines refer specifically to competitive athletes in various sports including those with high cardiovascular stress. This explains why Italian guidelines are more restrictive than European and USA ones. COCIS guidelines address 'sports doctors' who, in Italy, must certify fitness to participate in competitive sports. In Italy, this certificate is essential for participating in any competition.

Theoretical Investigation of the Mechanism by which A Gain-of-Function Mutation of the TRPM4 Channel Causes Conduction Block

In the heart, TRPM4 is most abundantly distributed in the conduction system. Previously, a single mutation, 'E7K', was identified in its distal N-terminus to cause conduction disorder because of enhanced cell-surface expression. It remains, however, unclear how this expression increase leads to conduction failure rather than abnormally enhanced cardiac excitability. To address this issue theoretically, we mathematically formulated the gating kinetics of the E7K-mutant TRPM4 channel by a combined use of voltage jump analysis and ionomycin-perforated cell-attached recording technique and incorporated the resultant rate constants of opening and closing into a human Purkinje fiber single-cell action potential (AP) model (Trovato model) to perform 1D-cable simulations. The results from TRPM4 expressing HEK293 cells showed that as compared with the wild-type, the open state is much preferred in the E7K mutant with increased voltage-and Ca²⁺-sensitivities. These theoretical predictions were confirmed by power spectrum and single channel analyses of expressed wild-type and E7K-mutant TRPM4 channels. In our modified Trovato model, the facilitated opening of the E7K mutant channel markedly prolonged AP duration with concomitant depolarizing shifts of the resting membrane potential in a manner dependent on the channel density (or maximal activity). This was, however, little evident in the wild-type TRPM4 channel. Moreover, 1D-cable simulations with the modified Trovato model revealed that increasing the density of E7K (but not of wild-type) TRPM4 channels progressively reduced AP conduction velocity eventually culminating in complete conduction block. These results clearly suggest the brady-arrhythmogenicity of the E7K mutant channel which likely results from its pathologically enhanced activity.

An Arrhythmic Mutation E7K Facilitates TRPM4 Channel Activation via Enhanced PIP2 Interaction

A Ca²⁺-activated monovalent cation-selective TRPM4 channel is abundantly expressed in the heart. Recently, a single gain-of-function mutation identified in the distal N-terminus of the human TRPM4 channel (Glu⁵ to Lys⁵; E7K) was found to be arrhythmogenic because of enhanced cell membrane expression. In this study, we conducted detailed analyses of this mutant channel from more functional aspects, in comparison with its wild type (WT). In an expression system, intracellular application of a short soluble PIP₂ (diC₈PIP₂) restored the single-channel activities of both WT and E7K, which had quickly faded after membrane excision. The potency (K_d) of diC₈PIP₂ for this recovery was stronger in E7K than its WT (1.44 vs. 2.40 μM). FRET-based PIP₂ measurements combined with the Danio rerio voltage-sensing phosphatase (DrVSP) and patch clamping revealed that lowering the endogenous PIP₂ level by DrVSP activation reduced the TRPM4 channel activity. This effect was less prominent in E7K than its WT (apparent K_d values estimated from DrVSP-mediated PIP₂ depletion: 0.97 and 1.06 μM, respectively), being associated with the differential PIP₂-mediated modulation of voltage dependence. Moreover, intracellular perfusion of short N-terminal polypeptides containing either the ‘WT’ or ‘E7K’ sequences respectively attenuated the TRPM4 channel activation at whole-cell and single-channel levels, but in both configurations, the E7K polypeptide exerted greater inhibitory effects. These results collectively suggest that N-terminal interaction with endogenous PIP₂ is essential for the TRPM4 channel to function, the extent of which may be abnormally strengthened by the E7K mutation through modulating voltage-dependent activation. The altered PIP₂ interaction may account for the arrhythmogenic potential of this mutation.

Pharmacologic Approach to Sinoatrial Node Dysfunction

The spontaneous activity of the sinoatrial node initiates the heartbeat. Sino-atrial node dysfunction (SND) and sick sinoatrial (sick sinus) syndrome are caused by the heart's inability to generate a normal sinoatrial node action potential. In clinical practice, SND is generally considered an age-related pathology, secondary to degenerative fibrosis of the heart pacemaker tissue. However, other forms of SND exist, including idiopathic primary SND, which is genetic, and forms that are secondary to cardiovascular or systemic disease. The incidence of SND in the general population is expected to increase over the next half century, boosting the need to implant electronic pacemakers. During the last two decades, our knowledge of sino-atrial node physiology and of the pathophysiological mechanisms underlying SND has advanced considerably. This review summarizes the current knowledge about SND mechanisms and discusses the possibility of introducing new pharmacologic therapies for treating SND.

Clinical evidence-guided network pharmacology analysis reveals a critical contribution of β1-adrenoreceptor upregulation to bradycardia alleviation by Shenxian-Shengmai

Background

Shenxian-Shengmai (SXSM) Oral Liquid is a CFDA-approved patent Chinese Herbal medicine, which has been clinically used for the treatment of bradycardia. However, its active components and action mechanism remain to be established. The present study aimed to evaluate the efficacy of SXSM on bradycardia and to identify the possible active components and their pharmacological targets for this action.

Methods

A literature-based meta-analysis was performed to evaluate the clinical efficacy of SXSM on bradycardia, which was confirmed by a rat ex vivo cardiac model. Network pharmacology analysis was then conducted to reveal the potential targets of SXSM active components and their anti-arrhythmia mechanisms. Finally, the identified drug-target interaction was confirmed by immunofluorescence assay in cardiomyocyte.

Results

Meta-analysis of the available clinical study data shows that Shenxian-Shengmai Oral Liquid has a favorable effect for bradycardia. In an ex vivo bradycardia model of rat heart, SXSM restored heart rate by affecting Heart rate variability (HRV) which is associated with autonomic nervous system activity. A drug-target-pathway network analysis connecting SXSM components with arrhythmia suggested that a prominent anti-arrhythmia mechanisms of SXSM was via β1-adrenergic signaling pathway, which was subsequently validated by immunofluorescence assay showing that SXSM indeed increased the expression of ADRB1 in cultured cardiomyocytes.

Conclusion

By combining approaches of clinical evidence mining, experimental model confirmation, network pharmacology analyses and molecular mechanistic validation, we show that SXSM is an effective treatment for bradycardia and it involves multiple component interacting via multiple pathways, among which is the critical β1-adrenergic receptor upregulation. Our integrative approach could be applied to other multi-component traditional Chinese medicine investigation where ample clinical data are accumulated but advanced mechanistic studies are lacking.

Muscular dystrophy with arrhythmia caused by loss-of-function mutations in BVES

Objective

To study the genetic and phenotypic spectrum of patients harboring recessive mutations in BVES.

Methods

We performed whole-exome sequencing in a multicenter cohort of 1929 patients with a suspected hereditary myopathy, showing unexplained limb-girdle muscular weakness and/or elevated creatine kinase levels. Immunohistochemistry and mRNA experiments on patients' skeletal muscle tissue were performed to study the pathogenicity of identified loss-of-function (LOF) variants in BVES.

Results

We identified 4 individuals from 3 families harboring homozygous LOF variants in BVES, the gene that encodes for Popeye domain containing protein 1 (POPDC1). Patients showed skeletal muscle involvement and cardiac conduction abnormalities of varying nature and severity, but all exhibited at least subclinical signs of both skeletal muscle and cardiac disease. All identified mutations lead to a partial or complete loss of function of BVES through nonsense-mediated decay or through functional changes to the POPDC1 protein.

Conclusions

We report the identification of homozygous LOF mutations in BVES, causal in a young adult-onset myopathy with concomitant cardiac conduction disorders in the absence of structural heart disease. These findings underline the role of POPDC1, and by extension, other members of this protein family, in striated muscle physiology and disease. This disorder appears to have a low prevalence, although it is probably underdiagnosed because of its striking phenotypic variability and often subtle yet clinically relevant manifestations, particularly concerning the cardiac conduction abnormalities.