Beta1-adrenoceptor polymorphism predicts flecainide action in patients with atrial fibrillation

Precision Medicine Approaches to Cardiac Arrhythmias: JACC Focus Seminar 4/5

In the initial 3 papers in this Focus Seminar series, the fundamentals and key concepts of precision medicine were reviewed, followed by a focus on precision medicine in the context of vascular disease and cardiomyopathy. For the remaining 2 papers, we focus on precision medicine in the context of arrhythmias. Specifically, in this fourth paper we focus on long QT syndrome, Brugada syndrome, and atrial fibrillation. The final (fifth) paper will deal with catecholaminergic polymorphic ventricular tachycardia. These arrhythmias represent a spectrum of disease ranging from common to relatively rare, with very different genetic and environmental causative factors, and with differing clinical manifestations that range from almost no consequences to lethality in childhood or adolescence if untreated. Accordingly, the emerging precision medicine approaches to these arrhythmias vary significantly, but several common themes include increased use of genetic testing, avoidance of triggers, and personalized risk stratification to guide the use of arrhythmia-specific therapies.

New methodological approaches to atrial fibrillation drug discovery

INTRODUCTION

Atrial fibrillation (AF) is the most common arrhythmia encountered in clinical practice and rhythm control using pharmacological agents is required in selected patients. Nonetheless, current medication is only modestly efficacious and associated with significant cardiovascular and systemic side effects. More efficacious and safe drugs are required to restore and maintain sinus rhythm in patients with AF.

AREAS COVERED

In this review, several potential drug targets are discussed including trans-membrane ion channels, intracellular calcium signaling, gap junction signaling, atrial inflammation and fibrosis, and the autonomic nervous system. New tools and methodologies for AF drug development are also reviewed including gene therapy, genome-guided therapy, stem cell technologies, tissue engineering, and optogenetics.

EXPERT OPINION

In recent decades, there has been an increased understanding of the underlying pathogenesis of AF. As a result, there is a gradual paradigm shift from focusing only on trans-membrane ion channel inhibition to developing therapeutic agents that target other underlying arrhythmogenic mechanisms. Gene therapy and genome-guided therapy are emerging as novel treatments for AF with some success in proof-of-concept studies. Recent advances in stem cell technology, tissue engineering, and optogenetics may allow more effective in-vitro drug screening than conventional methodologies.

Polymorphism of the Beta-1 Gly389Arg receptor in patients with dual atrioventricular nodal physiology

Introduction

Gly389Arg β1 adrenergic receptor polymorphisms seem to exert an influence on the modulation of the adrenergic effect in several types of patients. This study aimed to determine the prevalence of Gly389Arg polymorphisms among patients with evidence of double nodal pathway and to correlate the electrophysiological properties with the different genotypes of the respective polymorphisms.

Methods

A cross-sectional, descriptive and analytical study was designed to assess 49 patients, with evidence of double nodal pathway, submitted to electrophysiological study. Genomic DNA was extracted from peripheral blood leukocytes and the genotypes of the Arg389Gly polymorphisms were identified in all individuals by PCR/RFLP (polymerase chain reaction/restriction fragment length polymorphism).

Results

The majority of patients were female and had supraventricular tachycardia (75.5%). The prevalence of Arg389Arg genotype was found in 32 patients (65.3%), Arg389Gly genotype in 16 patients (32.7%) and Gly389Gly genotype in 1 patient (2%). With respect to the induction of nodal reentrant tachycardia, it was possible to induce non-isoproterenol tachycardia in 32 patients (65.3%), of whom 24 had the Arg389Arg genotype and 8 the Arg389Gly and Gly389Gly genotype (p = 0.05). The resting heart rate of patients of the Arg389Arg genotype was 81 ± 18 bpm and the Arg389Gly and Gly389Gly genotype of 71 ± 9 bpm (p = 0.044). Body mass index (BMI) among patients with genotype Arg389Gly and Gly389Gly was 29.8 ± 7.1 and patients with the Arg389Arg genotype was 26.2 ± 4.6 (p = 0.034).

Conclusion

The Arg389Arg genotype was more easily related to triggering arrhythmia, higher resting heart rate and lower BMI.

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The Arg389Arg genotype was more easily related to triggering arrhythmia.

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Patients with Gly389 allele had difficulty in triggering nodal reentry tachycardia.

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There is relationship between the Arg389Gly polymorphism and the higher BMI.

The Genetic Puzzle of Familial Atrial Fibrillation

Atrial fibrillation (AF) is the most common clinical tachyarrhythmia. In Europe, AF is expected to reach a prevalence of 18 million by 2060. This estimate will increase hospitalization for AF to 4 million and 120 million outpatient visits. Besides being an independent risk factor for mortality, AF is also associated with an increased risk of morbidities. Although there are many well-defined risk factors for developing AF, no identifiable risk factors or cardiac pathology is seen in up to 30% of the cases. The heritability of AF has been investigated in depth since the first report of familial atrial fibrillation (FAF) in 1936. Despite the limited value of animal models, the advances in molecular genetics enabled identification of many common and rare variants related to FAF. The importance of AF heritability originates from the high prevalence of lone AF and the lack of clear understanding of the underlying pathophysiology. A better understanding of FAF will facilitate early identification of people at high risk of developing FAF and subsequent development of more effective management options. In this review, we reviewed FAF epidemiological studies, identified common and rare variants, and discussed their clinical implications and contributions to developing new personalized therapeutic strategies.

Emerging pharmacotherapies for the treatment of atrial fibrillation

INTRODUCTION

The main aim of current research on the field of atrial fibrillation (AF) treatment is to find new antiarrhythmic drugs with less side effects. Areas covered: Dronedarone and vernakalant showed promising result in term of efficacy and safety in selected patients. Ranolazine and colchicine are obtaining a role as a potential antiarrhythmic drug. Ivabradine is used in experimental studies for the rate control of AF. Moreover, new compounds (vanoxerine, moxonidine, budiodarone) are still under investigation. Monoclonal antibodies or selective antagonist of potassium channel are under investigation for long term maintenance of sinus rhythm. Clinical evidence and new pharmacological investigation on new drugs will be accurately reviewed in this article. Expert opinion: Dronedarone use is not recommended in patients with symptomatic heart failure (HF), NYHA class III-IV, depressed ventricular function and permanent AF, especially in patients assuming a concomitant therapy with digoxin. Vernakalant had superior efficacy than amiodarone, flecainide and propafenone in single studies and similar efficacy to direct current cardioversion. Several of the developing drugs examined in this paper show an interesting potential, in particular the research on selective ionic channel inhibition and on compounds which reduce the inflammation state, especially after ablation or surgery.

β1-Adrenergic receptor Arg389Gly polymorphism affects the antiarrhythmic efficacy of flecainide in patients with coadministration of β-blockers

OBJECTIVE

β1-Adrenergic receptor (β1-AR) stimulation modulates the antiarrhythmic activities of sodium channel blockers. The β1-AR Gly389 variant shows a marked decrease in agonist-stimulated cyclic AMP production compared with that of the wild-type Arg389 in vitro. We investigated whether the Arg389Gly polymorphism affects the efficacy of flecainide, a typical sodium channel blocker, in patients with or without coadministration of β-blockers.

METHODS

The effects of the β1-AR Arg389Gly polymorphism on the antiarrhythmic efficacy of flecainide were compared between with and without coadministered β-blockers in 159 patients with supraventricular tachyarrhythmia. The antiarrhythmic efficacy of flecainide was assessed for at least 2 months by evaluating symptomatology, 12-lead ECGs, and Holter monitoring results.

RESULTS

Genetic differences in the antiarrhythmic efficacy of flecainide were observed in patients with coadministration of β-blockers. Tachyarrhythmia was well controlled in 60% of Arg389-homozygotes, 30% of Gly389-heterozygotes, and 0% of Gly389-homozygotes (P=0.001). In contrast, no difference in the antiarrhythmic efficacy was observed among the three genotypes in the patients without coadministration of β-blockers (64, 70, and 60%, respectively). Heart rate in tachyarrhythmia in patients treated with flecainide was significantly higher in Gly389 carriers than in Arg389-homozygotes (P=0.013).

CONCLUSION

The Gly389 polymorphism decreased the antiarrhythmic efficacy of flecainide when coadministered with β-blockers. The results indicate that the Arg389Gly polymorphism may play an important role in predicting the efficacy of flecainide in patients with coadministration of β-blockers.

G protein-coupled receptor kinase 5 gene polymorphisms are associated with postoperative atrial fibrillation after coronary artery bypass grafting in patients receiving β-blockers

BACKGROUND

We hypothesized that genetic variations in the adrenergic signaling pathway and cytochrome P450 2D6 enzyme are associated with new-onset atrial fibrillation (AF) in patients who underwent coronary artery bypass grafting and were treated with perioperative β-blockers (BBs).

METHODS AND RESULTS

Two cohorts of patients who underwent coronary artery bypass grafting and received perioperative BBs at Duke University Medical Center were studied. In a discovery cohort of 563 individuals from the Perioperative Genetics and Safety Outcomes Study (PEGASUS), using a covariate-adjusted logistic regression analysis, we tested 492 single-nucleotide polymorphisms (SNPs) in 10 candidate genes of the adrenergic signaling pathway and cytochrome P450 2D6 for association with postoperative AF despite perioperative BB therapy. SNPs meeting a false discovery rate ≤0.20 (P<0.002) were then tested in the replication cohort of 245 individuals from the Catheterization Genetics biorepository. Of the 492 SNPs examined, 4 intronic SNPs of the G protein-coupled kinase 5 (GRK5) gene were significantly associated with postoperative AF despite perioperative BB therapy in the discovery cohort with additive odds ratios between 1.72 and 2.75 (P=4.78×10(-5) to 0.0015). Three of these SNPs met nominal significance levels in the replication cohort with odds ratios between 2.07 and 2.60 (P=0.007 to 0.016). However, meta-analysis of the 2 data sets cohorts suggested strong association with postoperative AF despite perioperative BB therapy in all 4 SNPs (meta-P values from 1.66×10(-6) to 3.39×10(-5)).

CONCLUSIONS

In patients undergoing coronary artery bypass grafting, genetic variation in GRK5 is associated with postoperative AF despite perioperative BB therapy.

Genetic mechanisms of atrial fibrillation: impact on response to treatment

Atrial fibrillation (AF) is the most-common sustained arrhythmia observed in clinical practice, but response to therapy is highly variable between patients. Current drug therapies to suppress AF are incompletely and unpredictably effective and carry substantial risk of proarrhythmia and noncardiac toxicities. The limited success of therapy for AF is partially the result of heterogeneity of the underlying substrate, interindividual differences in disease mechanisms, and our inability to predict response to therapies in individual patients. In this Review, we discuss the evidence that variability in response to drug therapy is also conditioned by the underlying genetic substrate for AF. Increased susceptibility to AF is mediated through diverse genetic mechanisms, including modulation of the atrial action-potential duration, conduction slowing, and impaired cell-to-cell communication, as well as novel mechanisms, such as regulation of signalling proteins important in the pathogenesis of AF. However, the translation of genetic data to the care of the patients with AF has been limited because of poor understanding of the underlying mechanisms associated with common AF-susceptibility loci, a dearth of prospective, adequately powered studies, and the challenges associated with determining efficacy of antiarrhythmic drugs. What is apparent, however, is the need for appropriately designed, genotype-directed clinical trials.

Diagnostic accuracy of NT-proBNP ratio (BNP-R) for early diagnosis of tachycardia-mediated cardiomyopathy: a pilot study

BACKGROUND

When heart failure and tachycardia occur simultaneously, a useful diagnostic tool for early discrimination of patients with benign tachycardia-mediated cardiomyopathy (TMC) versus major structural heart disease (MSHD) is not available. Such a tool is required to prevent unnecessary and wearing diagnostics in patients with reversible TMC. Moreover, it could lead to early additional diagnostics and therapeutic approaches in patients with MSHD.

METHODS

A total of 387 consecutive patients with supraventricular arrhythmia underwent assessment at a single center. Of these patients, 40 fulfilled the inclusion criteria with a resting heart rate ≥100 bpm and an impaired left ventricular ejection fraction <40%. In all patients, successful electrical cardioversion was performed. At baseline, day 1 and weekly for 4 weeks, levels of NT-proBNP and echocardiographic parameters were evaluated. An NT-proBNP ratio (BNP-R) was calculated as a quotient of baseline NT-proBNP/follow-up NT-proBNP. After 4 weeks, cardiac catheterization was performed to identify patients with a final diagnosis of TMC versus MSHD.

RESULTS

Initial NT-proBNP concentrations were elevated and consecutively decreased after cardioversion in all patients. Multivariate regression and ROC analysis revealed that BNP-R discriminated between patients with TMC versus MSHD independent and superior to all other variables. The area under the ROC curve for BNP-R to detect TMC was 0.90 (95% CI 0.79-1.00; p < 0.001) after 1 week and 0.995 (95% CI 0.99-1.00; p < 0.0001) after 4 weeks. One week after cardioversion already, a BNP-R cutoff ≥2.3 was useful for TMC diagnosis indicated by an accuracy of 90%, sensitivity of 84% and specificity of 95%.

CONCLUSION

BNP-R was found to be highly accurate for the early diagnosis of TMC.