Interaction of ischaemia and encainide/flecainide treatment: a proposed mechanism for the increased mortality in CAST I

The opioid tramadol blocks the cardiac sodium channel Nav1.5 in HEK293 cells

AIMS

Opioids are associated with increased risk of sudden cardiac death. This may be due to their effects on the cardiac sodium channel (Nav1.5) current. In the present study, we aim to establish whether tramadol, fentanyl, or codeine affects Nav1.5 current.

METHODS AND RESULTS

Using whole-cell patch-clamp methodology, we studied the effects of tramadol, fentanyl, and codeine on currents of human Nav1.5 channels stably expressed in HEK293 cells and on action potential (AP) properties of freshly isolated rabbit ventricular cardiomyocytes. In fully available Nav1.5 channels (holding potential -120 mV), tramadol exhibited inhibitory effects on Nav1.5 current in a concentration-dependent manner with an IC50 of 378.5 ± 33.2 µm. In addition, tramadol caused a hyperpolarizing shift of voltage-gated (in)activation and a delay in recovery from inactivation. These blocking effects occurred at lower concentrations in partially inactivated Nav1.5 channels: during partial fast inactivation (close-to-physiological holding potential -90 mV), IC50 of Nav1.5 block was 4.5 ± 1.1 μm, while it was 16 ± 4.8 μm during partial slow inactivation. The tramadol-induced changes on Nav1.5 properties were reflected by a reduction in AP upstroke velocity in a frequency-dependent manner. Fentanyl and codeine had no effect on Nav1.5 current, even when tested at lethal concentrations.

CONCLUSION

Tramadol reduces Nav1.5 currents, in particular, at close-to-physiological membrane potentials. Fentanyl and codeine have no effects on Nav1.5 current.

Carbamazepine Increases the Risk of Sudden Cardiac Arrest by a Reduction of the Cardiac Sodium Current

Aim: To assess the risk of sudden cardiac arrest (SCA) associated with the use of carbamazepine (CBZ) and establish the possible underlying cellular electrophysiological mechanisms.

Methods: The SCA risk association with CBZ was studied in general population cohorts using a case–control design (n = 5,473 SCA cases, 21,866 non-SCA controls). Effects of 1–100 µM CBZ on action potentials (APs) and individual membrane currents were determined in isolated rabbit and human cardiomyocytes using the patch clamp technique.

Results: CBZ use was associated with increased risk of SCA compared with no use (adjusted odds ratio 1.90 [95% confidence interval: 1.12–3.24]). CBZ reduced the AP upstroke velocity of rabbit and human cardiomyocytes, without prominent changes in other AP parameters. The reduction occurred at ≥30 µM and was frequency-dependent with a more pronounced reduction at high stimulus frequencies. The cardiac sodium current (I_Na) was reduced at ≥30 μM; this was accompanied by a hyperpolarizing shift in the voltage-dependency of inactivation. The recovery from inactivation was slower, which is consistent with the more pronounced AP upstroke velocity reduction at high stimulus frequencies. The main cardiac K⁺ and Ca²⁺ currents were unaffected, except reduction of L-type Ca²⁺ current by 100 µM CBZ.

Conclusion: CBZ use is associated with an increased risk of SCA in the general population. At concentrations of 30 µM and above, CBZ reduces AP upstroke velocity and I_Na in cardiomyocytes. Since the concentration of 30 µM is well within the therapeutic range (20–40 µM), we conclude that CBZ increases the risk of SCA by a reduction of the cardiac I_Na.

Absent or Mild Coronary Calcium Predicts Low-Risk Stress Test Results and Outcomes in Patients Considered for Flecainide Therapy

BACKGROUND

Flecainide is a useful antiarrhythmic for atrial fibrillation (AF). However, because of ventricular proarrhythmia risk, a history of myocardial infarction (MI) or coronary artery disease (CAD) is a flecainide exclusion, and stress testing is used to exclude ischemia. We assessed whether absent/mild coronary artery calcium (CAC) can supplement or avoid the need for stress testing.

METHODS

We assessed ischemic burden using regadenoson Rb-82 PET/CT in 1372 AF patients ≥50 years old without symptoms or signs of clinical CAD. CAC was determined qualitatively by low dose attenuation computed tomography (CT) (n = 816) or by quantitative CT (n = 556). Ischemic burden and clinical outcomes were compared by CAC burden.

RESULTS

Patients with CAC absent or mild (n = 766, 57.2%) were younger, more frequently female, and had higher BMI but lower rates of diabetes, hypertension, and dyslipidemia. Average ischemic burden was lower in CAC-absent/mild patients, and CAC-absent/mild patients showed greater coronary flow reserve, had fewer referrals for coronary angiography, and less often had obstructive CAD. Revascularization at 90 days was lower, and the rate of longer-term major adverse cardiovascular events was favorable.

CONCLUSIONS

An easily administered, inexpensive, low radiation CAC scan can identify a subset of flecainide candidates with a low ischemic burden on PET stress testing that rarely needs coronary angiography/intervention and has favorable outcomes. Absent or mild CAC-burden combined with other clinical information may avoid or complement routine stress testing. However, additional, ideally randomized and multicenter trials are indicated to confirm these findings before replacing stress testing with CAC screening in selecting patients for flecainide therapy in clinical practice.

Diagnostic role of coronary CT angiography in paroxysmal or first diagnosed atrial fibrillation

OBJECTIVES

The presence of coronary artery disease (CAD) in patients hospitalised with paroxysmal or first diagnosed atrial fibrillation (AF) has major implications for antithrombotic therapy and cardiovascular event rate. Coronary CT angiography (CCTA) is a feasible tool to identify patients with concealed CAD. We aimed to evaluate the diagnostic role of early CCTA in patients hospitalised with paroxysmal or first diagnosed AF.

METHODS

In a 5-year single-centre retrospective analysis, 566 patients with paroxysmal or first diagnosed AF who underwent CCTA were enrolled to investigate the presence of CAD.

RESULTS

In patients with paroxysmal or first diagnosed AF, CCTA revealed CAD (coronary artery stenosis ≥50%) in 39.2%. Cardiac catheterisation was performed in 31.6%, confirming CAD in 13.1% of all patients. In 8.0% percutaneous coronary intervention and in 0.5% coronary artery bypass grafting was performed. In patients with paroxysmal or first diagnosed AF: (1) angina pectoris per se does not predict CAD; (2) multivariable regression analysis revealed age, male sex and diabetes as risk factors for CAD in AF; (3) Framingham Risk Score for coronary heart disease and CHA2DS2-VASc-Score were relevant risk scores of CAD and (4) the classification of Coronary Artery Calcium score reference values according to the Multi-Ethnic Study of Atherosclerosis was a predictor of CAD.

CONCLUSION

Patients with paroxysmal or first diagnosed AF are at risk for CAD, while CCTA is a feasible diagnostic tool for CAD. We recommend to integrate CT calcium scoring and CCTA into the diagnostic workup of patients with new-onset or paroxysmal AF.

Nanotechnology-assisted microfluidic systems: from bench to bedside

With significant advancements in research technologies, and an increasing global population, microfluidic and nanofluidic systems (such as point-of-care, lab-on-a-chip, organ-on-a-chip, etc) have started to revolutionize medicine. Devices that combine micron and nanotechnologies have increased sensitivity, precision and versatility for numerous medical applications. However, while there has been extensive research on microfluidic and nanofluidic systems, very few have experienced wide-spread commercialization which is puzzling and deserves our collective attention. For the above reasons, in this article, we review research advances that combine micro and nanotechnologies to create the next generation of nanomaterial-based microfluidic systems, the latest in their commercialization success and failure and highlight the value of these devices both in industry and in the laboratory.

Electrophysiological and anatomical factors determine arrhythmic risk in acute myocardial ischaemia and its modulation by sodium current availability

Acute myocardial ischaemia caused by coronary artery disease is one of the main causes of sudden cardiac death. Even though sodium current blockers are used as anti-arrhythmic drugs, decreased sodium current availability, also caused by mutations, has been shown to increase arrhythmic risk in ischaemic patients. The mechanisms are still unclear. Our goal is to exploit perfect control and data transparency of over 300 high-performance computing simulations to investigate arrhythmia mechanisms in acute myocardial ischaemia with variable sodium current availability. The human anatomically based torso-biventricular electrophysiological model used includes representation of realistic ventricular anatomy and fibre architecture, as well as ionic to electrocardiographic properties. Simulations show that reduced sodium current availability increased arrhythmic risk in acute regional ischaemia due to both electrophysiological (increased dispersion of refractoriness across the ischaemic border zone) and anatomical factors (conduction block from the thin right ventricle to thick left ventricle). The asymmetric ventricular anatomy caused high arrhythmic risk specifically for ectopic stimuli originating from the right ventricle and ventricular base. Increased sodium current availability was ineffective in reducing arrhythmic risk for septo-basal ectopic excitation. Human-based multiscale modelling and simulations reveal key electrophysiological and anatomical factors determining arrhythmic risk in acute ischaemia with variable sodium current availability.

Prognostic Value of Subclinical Coronary Artery Disease in Atrial Fibrillation Patients Identified by Coronary Computed Tomography Angiography

Identifying coronary artery disease (CAD) in atrial fibrillation (AF) patients improves risk stratification and defines clinical management. However, the value of screening for subclinical CAD with cardiac CT in AF patients is unknown. Between 2011 and 2015, 94 consecutive patients without known or suspected CAD (66 (57-73) years, 68% male), who were referred for AF evaluation, underwent a noncontrast-enhanced coronary calcium scan and a coronary computed tomography angiography (CCTA) at our center. We retrospectively evaluated the coronary calcium score, the prevalence of obstructive CAD (≥50% stenosis) determined by CCTA, compared clinical management and 5-year outcome in patients with and without obstructive CAD on CCTA, and examined the potential impact of a coronary calcium score and obstructive CAD on CCTA as a manifestation of vascular disease on the CHA2Ds2VASc score and for the cardiovascular risk stratification of AF patients. The median coronary calcium score was 57 (0-275) and 24 patients (26%) had obstructive CAD on CCTA. At baseline, patients with obstructive CAD more often used statins than those without obstructive CAD (54% vs 26%, p = 0.011). After a median clinical follow-up of 2.4 (0.5-4.5) years, patients with obstructive CAD more frequently used oral anticoagulant and/or antiplatelet drugs, statins, angiotensin-II-receptor blockers and/or angiotensin-converting-enzyme inhibitors, and less often used class I antiarrhythmic drugs than patients without obstructive CAD (all p <0.050). After a median follow-up of 5.7 (4.8-6.8) years, mortality was higher in patients with obstructive CAD than in those without obstructive CAD (29% vs 11%, log-rank test: p = 0.034). Implementation of a coronary calcium score and/or obstructive CAD on CCTA elevated the CHA2Ds2VASc score and cardiovascular risk stratification in 42 patients (p <0.001) and 47 patients (p = 0.006), respectively. In conclusion, we observed a high prevalence of obstructive CAD on CCTA in AF patients without known or suspected CAD. AF patients with obstructive CAD were managed differently and had a worse prognosis than those without obstructive CAD. Cardiac CT could enhance cardiovascular risk stratification of AF patients.

Use of Flecainide for the Treatment of Atrial Fibrillation

Atrial fibrillation (AF) is the most common sustained arrhythmia and is associated with substantial morbidity and impairment of quality of life. Restoration and maintenance of normal sinus rhythm is a desirable goal for many patients with AF; however, this strategy is limited by the relatively small number of antiarrhythmic drugs (AADs) available for AF rhythm control. Although it is recommended in current medical guidelines as first-line therapy for patients without structural heart disease, the use of flecainide has been curtailed since the completion of the Cardiac Arrhythmia Suppression Trial. In clinical trials and real-world use, flecainide has proven to be more effective than other AADs for the acute termination of recent onset AF. Flecainide is also moderately effective and, with the exception of amiodarone, equivalent to other AADs for the chronic suppression of paroxysmal and persistent AF. In patients without structural heart disease, flecainide has been demonstrated to be safe and well tolerated relative to other AADs. Despite this favorable profile, flecainide is underutilized, likely due to a perceived risk of ventricular proarrhythmia, a concern that has not been borne out in patients without underlying structural heart disease. Guidelines for administration and use of flecainide are summarized in this review.

Multiple targets for flecainide action: implications for cardiac arrhythmogenesis

Flecainide suppresses cardiac tachyarrhythmias including paroxysmal atrial fibrillation, supraventricular tachycardia and arrhythmic long QT syndromes (LQTS), as well as the Ca2+ -mediated, catecholaminergic polymorphic ventricular tachycardia (CPVT). However, flecainide can also exert pro-arrhythmic effects most notably following myocardial infarction and when used to diagnose Brugada syndrome (BrS). These divergent actions result from its physiological and pharmacological actions at multiple, interacting levels of cellular organization. These were studied in murine genetic models with modified Nav channel or intracellular ryanodine receptor (RyR2)-Ca2+ channel function. Flecainide accesses its transmembrane Nav 1.5 channel binding site during activated, open, states producing a use-dependent antagonism. Closing either activation or inactivation gates traps flecainide within the pore. An early peak INa related to activation of Nav channels followed by rapid de-activation, drives action potential (AP) upstrokes and their propagation. This is diminished in pro-arrhythmic conditions reflecting loss of function of Nav 1.5 channels, such as BrS, accordingly exacerbated by flecainide challenge. Contrastingly, pro-arrhythmic effects attributed to prolonged AP recovery by abnormal late INaL following gain-of-function modifications of Nav 1.5 channels in LQTS3 are reduced by flecainide. Anti-arrhythmic effects of flecainide that reduce triggering in CPVT models mediated by sarcoplasmic reticular Ca2+ release could arise from its primary actions on Nav channels indirectly decreasing [Ca2+ ]i through a reduced [Na+ ]i and/or direct open-state RyR2-Ca2+ channel antagonism. The consequent [Ca2+ ]i alterations could also modify AP propagation velocity and therefore arrhythmic substrate through its actions on Nav 1.5 channel function. This is consistent with the paradoxical differences between flecainide actions upon Na+ currents, AP conduction and arrhythmogenesis under circumstances of normal and increased RyR2 function.

LINKED ARTICLES

This article is part of a themed section on Spotlight on Small Molecules in Cardiovascular Diseases. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v175.8/issuetoc.

QT interval prolongation and torsade de pointes: Synergistic effect of flecainide and H1 receptor antagonists

A high percentage of patients having atrial fibrillation (AF) presents with paroxysmal AF. Flecainide, the prototypic class Ic anti-arrhythmic drug is the most effective drug to maintain sinus rhythm in this subgroup of patients, though the drug has potential pro-arrhythmic effects. Furthermore, the H₁ receptor antagonists are the most commonly prescribed drugs for the symptomatic treatment of pruritus. Despite having low number of adverse effects, the H₁ receptor antagonists have cardiotoxic effects. Flecainide and H₁ receptor antagonists present arrhythmic complications including QT interval prolongation and torsade de pointes (TdP). The case presented here is a 65-year-old female who was diagnosed of atrial fibrillation and presented with rashes in lower extremities. The patient was treated using flecainide and H₁ receptor antagonists (loratadine and hydroxyzine) that prolonged QT interval and induced TdP. The concomitant administration of flecainide and H₁ receptor antagonists seems to have a synergistic effect in QT interval prolongation and subsequent TdP. The concurrent administration of H₁ receptor antagonists to patients receiving class Ic anti-arrhythmic drugs should be avoided in order to reduce arrhythmic risk in this population.

Antiepileptic medications and the risk for sudden cardiac death caused by an acute coronary event: a prospective case-control study

BACKGROUND

Epilepsy is associated with sudden death, but the reasons for this association are not well known. Objective We studied the role of antiepileptic drugs (AEDs) as a factor contributing to sudden cardiac death (SCD) in The Finnish Study of the Genotype and Phenotype Characteristics of Sudden Cardiac Death (FinGesture).

METHODS AND RESULTS

The FinGesture study compares the characteristics of victims of SCD caused by an autopsy-verified acute coronary event (cases) vs. survivors of an acute coronary event (ACS) (controls). The study population comprised 3737 cases (mean age 64 ± 12 y) and 3081 controls (mean age 66 ± 12 y). The use of AED was obtained from death certificates, autopsy/hospital records, national drug imbursement register, and interviews with the relatives. AEDs were more commonly used by the victims of SCD vs. controls (5.5% vs. 2.2%, adjusted odds ratio 2.7, 95% CI; 1.9-3.9; p < 0001). The use of AED for non-epilepsy indications was also more common in the cases than in controls (1.5% vs. 1.0%, p = 0.005).

CONCLUSION

A higher rate of AED was observed in victims of SCD than in a control group of ACS patients. Concomitant use of AED could be responsible for a small fraction of deaths due to acute coronary events. Key message Epilepsy has been associated with sudden cardiac death. The use of antiepileptic drugs seems to be associated with an increased risk of sudden cardiac death during a coronary event. Physicians should be aware of the risk related to antiepileptic drugs especially when used for other reasons than epilepsy.

Investigation of the antifibrillatory drug interactions between Amiodarone and Ibutilide in isolated, perfused Rabbit hearts

In view of the reliability of the serial-shock method of measuring ventricular fibrillation threshold (VFT) in quantitatively assessing the antifibrillatory potency of many anti-arrhythmic drugs and the alarming reports of the proarrhythmic effects of several anti-arrhythmic agents, it was decided to use the above technique to study the possible interactions that may occur when anti-arrhythmic drugs from different classes are combined. Hearts isolated from New Zealand white rabbits of either sex weighing 1.5-2 kg were perfused by the Langendorff method with McEwen's solution. In six hearts, measurement of VFT was made in the absence of any drug throughout the experiments. Perfusion with either amiodarone or ibutilide produced significant, dose-dependent increase in VFT. In addition, there was no significant difference in the increase in VFT produced by the combined infusion of 1 μmol of amiodarone and 0.01 μmol of ibutilide and the summation of the increases produced by the separate infusion of these two concentrations. This is in contrast to a significant synergistic antifibrillatory effect of the combined use of lidocaine and propranolol that was reported previously. The lack of antifibrillatory interactions between amiodarone and Ibutilide may suggest the safety of combining the two drugs in the treatment of cardiac arrhythmias. However, further studies are required to establish this in the clinical setup.

Genetic, clinical and pharmacological determinants of out-of-hospital cardiac arrest: rationale and outline of the AmsteRdam Resuscitation Studies (ARREST) registry

Introduction

Out-of-hospital cardiac arrest (OHCA) is a major public health problem. Recognising the complexity of the underlying causes of OHCA in the community, we aimed to establish the clinical, pharmacological, environmental and genetic factors and their interactions that may cause OHCA.

Methods and analysis

We set up a large-scale prospective community-based registry (AmsteRdam Resuscitation Studies, ARREST) in which we prospectively include all resuscitation attempts from OHCA in a large study region in the Netherlands in collaboration with Emergency Medical Services. Of all OHCA victims since June 2005, we prospectively collect medical history (through hospital and general practitioner), and current and previous medication use (through community pharmacy). In addition, we include DNA samples from OHCA victims with documented ventricular tachycardia/fibrillation during the resuscitation attempt since July 2007. Various study designs are employed to analyse the data of the ARREST registry, including case–control, cohort, case only and case-cross over designs.

Ethics and dissemination

We describe the rationale, outline and potential results of the ARREST registry. The design allows for a stable and reliable collection of multiple determinants of OHCA, while assuring that the patient, lay-caregiver or medical professional is not hindered in any way. Such comprehensive data collection is required to unravel the complex basis of OHCA. Results will be published in peer-reviewed journals and presented at relevant scientific symposia.

Sudden cardiac death is associated both with epilepsy and with use of antiepileptic medications

OBJECTIVE

Epilepsy is associated with increased risk for sudden cardiac death (SCD). We aimed to establish, in a community based study, whether this association is mediated by epilepsy per se, use of antiepileptic medications (AEMs), or both.

METHODS

We studied SCD cases and age/sex matched controls in a case-control study in a large scale general practitioners' research database (n=478 661 patients). SCD risk for symptomatic epilepsy (seizure <2 years before SCD), stable epilepsy (no seizure <2 years before SCD), and use of AEMs (any indication) was determined.

RESULTS

We identified 926 SCD cases and 9832 controls. Fourteen cases had epilepsy. Epilepsy was associated with an increased SCD risk (cases 1.5%, controls 0.5%; adjusted OR 2.8, 95% CI 1.4 to 5.3). SCD risk was increased for symptomatic epilepsy (cases 0.9%, controls 0.1%; adjusted OR 5.8, 95% CI 2.1 to 15.6), but not with stable epilepsy (cases 0.6%, controls 0.4%; adjusted OR 1.6, 95% CI 0.7 to 4.1). AEM use was found in 23 cases and was associated with an increased SCD risk (cases 2.5%, controls 0.8%; adjusted OR overall 2.6, 95% CI 1.5 to 4.3) among symptomatic epilepsy cases (cases 0.9%, controls 0.1%; adjusted OR 6.4, 95% CI 2.4 to 17.4) and non-epilepsy cases (cases 1.0%, controls 0.4%; adjusted OR 2.3, 95% CI 1.01 to 5.2). Increased SCD risk was associated with sodium channel blocking AEMs (cases 1.6%, controls 0.4%; adjusted OR 2.8, 95% CI 1.1 to 7.2), but not with non-sodium channel blocking AEMs. Carbamazepine and gabapentin were associated with increased SCD risk (carbamazepine: cases 1.1%, controls 0.3%; adjusted OR 3.2, 95% CI 1.1 to 9.2; gabapentin: cases 0.3%, controls 0.1%; adjusted OR 5.7, 95% CI 1.2 to 27.9).

CONCLUSIONS

Epilepsy and AEM use are both associated with increased SCD risk in the general population. Poor seizure control contributes to increased SCD risk in epilepsy, while sodium channel blockade contributes to SCD susceptibility in AEM users.

Cardiac sodium channels and inherited electrophysiological disorders: an update on the pharmacotherapy

INTRODUCTION

Since the recognition of inherited sodium (Na(+)) channel disease, the cardiac Na(+) channel has been extensively studied. Both loss-of-function and gain-of-function mutations of the cardiac Na(+) channel are associated with cardiac arrhythmia and sudden cardiac death. Pathophysiological mechanisms that may induce arrhythmia are unravelled and include alterations in biophysical properties due to the mutation in SCN5A, drug use and circumstantial factors. Insights into the mechanisms of inherited Na(+) channel disease may result in tailored therapy. However, due to the complexity of cardiac electrical activity and pathophysiological mechanisms, pharmacotherapy in cardiac Na(+) channel disease remains challenging.

AREAS COVERED

This review discusses various mechanisms involved in inherited Na(+) channel disorders, focussing on Brugada syndrome (Brs) and long QT syndrome type 3 (LQTS3). It aims to provide an overview of developments in pharmacotherapy, discussing both treatment and which drugs to avoid to prevent arrhythmia.

EXPERT OPINION

Altered biophysical properties of cardiac Na(+) channels are the basis of arrhythmias in patients with inherited Na(+) channel diseases such as BrS and LQTS3. The effects of such biophysical derangements are strongly modulated by concomitant factors. Tailored drug therapy is required to prevent arrhythmia and is best achieved by educating patients affected by Na(+) channel disorders.

Targeting sodium channels in cardiac arrhythmia

Cardiac voltage-gated sodium channels are responsible for proper electrical conduction in the heart. During acquired pathological conditions and inherited sodium channelopathies, altered sodium channel function causes conduction disturbances and ventricular arrhythmias. Although the clinical, genetic and biophysical characteristics of cardiac sodium channel disease have been extensively studied, limited progress has been made in the development of treatment strategies targeting sodium channels. Classical non-selective sodium channel blockers have only limited clinical applicability, while more selective inhibitors of the late sodium current constitute a more promising treatment option. Because of our insufficient understanding of their complexity and subcellular diversity, other specific therapeutic targets for modulating sodium channels remain elusive. The current status and future potential of targeting sodium channels in cardiac arrhythmias are discussed.

Adherence to guideline recommendations for antiarrhythmic drugs in atrial fibrillation

BACKGROUND

Atrial fibrillation (AF) guideline recommendations for antiarrhythmic drugs (AADs) are based on the effectiveness and safety of the AAD in patients with selected, concomitant heart disease. It is unknown to what extent these recommendations are being implemented in clinical practice.

METHODS

Using commercial health claims, patients with AF were identified and then categorized into mutually exclusive, guideline-established subgroups based on their most serious concurrent heart disease: heart failure, coronary artery disease (CAD), hypertension, and no heart disease. Antiarrhythmic drug use after the first AF encounter and the identified concurrent heart disease encounter was determined from prescription claims, and this was compared with guideline recommendations.

RESULTS

From January 2006 through December 2010, a total of 331,274 patients with AF aged < 65 years were identified: 18%, heart failure; 23%, CAD; 33%, hypertension; and 25%, no heart disease. Of these, 78,877 (24%) patients filled ≥ 1 qualifying AAD prescription. The median age was 57 years (interquartile range 52-61), and 69% were male. A total of 74,191 patients had AADs after both the AF and concurrent heart disease encounters: 27% with heart failure, 25% with CAD, 21% with hypertension, and 19% with no heart disease. In the heart failure and CAD subgroups, 45% and 31% of AADs were inconsistent with first- or second-line guideline recommendations, respectively.

CONCLUSION

More than one-third of the AADs used in patients with AF and CAD or heart failure did not conform to guideline recommendations. This highlights the potential need for increased clinician education and intervention to improve the safe use of AADs for AF management.

Anti-Arrhythmic Agents in the Treatment of Atrial Fibrillation

Although atrial fibrillation (AF) is the most common sustained arrhythmia seen during daily cardiovascular physician practice, its management remained a challenge for cardiology physician as there was no single anti-arrhythmic agents proved to be effective in converting atrial fibrillation and kept its effectiveness in maintaining sinus rhythm over long term. Moreover all the anti-arrhythmic agents that are used in treatment of AF were potentially pro-arrhythmic especially in patients with coronary artery disease and structurally abnormal heart. Some of these drugs also have serious non cardiac side effects that limit its long term use in the management of atrial fibrillation. Several new and investigational anti-arrhythmic agents are emerging but data supporting their effectiveness and safety are still limited. In this systematic review we examine the efficacy and safety of these medications supported by the major published randomized trials, meta-analyses and review articles and conclude with a summary of guidelines recommendations.

Genome- and phenome-wide analyses of cardiac conduction identifies markers of arrhythmia risk

BACKGROUND

ECG QRS duration, a measure of cardiac intraventricular conduction, varies ≈2-fold in individuals without cardiac disease. Slow conduction may promote re-entrant arrhythmias.

METHODS AND RESULTS

We performed a genome-wide association study to identify genomic markers of QRS duration in 5272 individuals without cardiac disease selected from electronic medical record algorithms at 5 sites in the Electronic Medical Records and Genomics (eMERGE) network. The most significant loci were evaluated within the Cohorts for Heart and Aging Research in Genomic Epidemiology (CHARGE) consortium QRS genome-wide association study meta-analysis. Twenty-three single-nucleotide polymorphisms in 5 loci, previously described by CHARGE, were replicated in the eMERGE samples; 18 single-nucleotide polymorphisms were in the chromosome 3 SCN5A and SCN10A loci, where the most significant single-nucleotide polymorphisms were rs1805126 in SCN5A with P=1.2×10(-8) (eMERGE) and P=2.5×10(-20) (CHARGE) and rs6795970 in SCN10A with P=6×10(-6) (eMERGE) and P=5×10(-27) (CHARGE). The other loci were in NFIA, near CDKN1A, and near C6orf204. We then performed phenome-wide association studies on variants in these 5 loci in 13859 European Americans to search for diagnoses associated with these markers. Phenome-wide association study identified atrial fibrillation and cardiac arrhythmias as the most common associated diagnoses with SCN10A and SCN5A variants. SCN10A variants were also associated with subsequent development of atrial fibrillation and arrhythmia in the original 5272 "heart-healthy" study population.

CONCLUSIONS

We conclude that DNA biobanks coupled to electronic medical records not only provide a platform for genome-wide association study but also may allow broad interrogation of the longitudinal incidence of disease associated with genetic variants. The phenome-wide association study approach implicated sodium channel variants modulating QRS duration in subjects without cardiac disease as predictors of subsequent arrhythmias.

Effectiveness of prophylactic implantation of cardioverter-defibrillators without cardiac resynchronization therapy in patients with ischaemic or non-ischaemic heart disease: a systematic review and meta-analysis

Aims

Much controversy exists concerning the efficacy of primary prophylactic implantable cardioverter-defibrillators (ICDs) in patients with low ejection fraction due to coronary artery disease (CAD) or dilated cardiomyopathy (DCM). This is also related to the bias created by function improving interventions added to ICD therapy, e.g. resynchronization therapy. The aim was to investigate the efficacy of ICD-only therapy in primary prevention in patients with CAD or DCM.

Methods and results

Public domain databases, MEDLINE, EMBASE, and Cochrane Central Register of Controlled Trials, were searched from 1980 to 2009 for randomized clinical trials of ICD vs. conventional therapy. Two investigators independently abstracted the data. Pooled estimates were calculated using both fixed-effects and random-effects models. Eight trials were included in the final analysis (5343 patients). Implantable cardioverter-defibrillators significantly reduced the arrhythmic mortality [relative risk (RR): 0.40; 95% confidence interval (CI): 0.27–0.67] and all-cause mortality (RR: 0.73; 95% CI: 0.64–0.82). Regardless of aetiology of heart disease, ICD benefit was similar for CAD (RR: 0.67; 95% CI: 0.51–0.88) vs. DCM (RR: 0.74; 95% CI: 0.59–0.93).

Conclusions

The results of this meta-analysis provide strong evidence for the beneficial effect of ICD-only therapy on the survival of patients with ischaemic or non-ischaemic heart disease, with a left ventricular ejection fraction ≤35%, if they are 40 days from myocardial infarction and ≥3 months from a coronary revascularization procedure.

Twenty-five years in the making: flecainide is safe and effective for the management of atrial fibrillation

Atrial fibrillation (AF) is the most common arrhythmia in clinical practise and its prevalence is increasing. Over the last 25 years, flecainide has been used extensively worldwide, and its capacity to reduce AF symptoms and provide long-term restoration of sinus rhythm (SR) has been well documented. The increased mortality seen in patients treated with flecainide in the Cardiac Arrhythmia Suppression Trial (CAST) study, published in 1991, still deters many clinicians from using flecainide, denying many new AF patients a valuable treatment option. There is now a body of evidence that clearly demonstrates that flecainide has a favourable safety profile in AF patients without significant left ventricular disease or coronary heart disease. As a result of this evidence, flecainide is now recommended as one of the first-line treatment options for restoring and maintaining SR in patients with AF under current treatment guidelines. The objective of this article is to review the literature pertaining to the pharmacological characteristics, safety and efficacy of flecainide, and to place this drug in the context of current therapeutic management strategies for AF.

Predicting drug-induced slowing of conduction and pro-arrhythmia: identifying the 'bad' sodium current blockers

BACKGROUND AND PURPOSE

The regulatory guidelines (ICHS7B) for the identification of only drug-induced long QT and pro-arrhythmias have certain limitations.

EXPERIMENTAL APPROACH

Conduction time (CT) was measured in isolated Purkinje fibres, left ventricular perfused wedges and perfused hearts from rabbits, and sodium current was measured in Chinese hamster ovary cells, transfected with Na(v)1.5 channels.

KEY RESULTS

A total of 355 compounds were screened for their effects on CT: 32% of these compounds slowed conduction, 65% had no effect and 3% accelerated conduction. Lidocaine and flecainide, which slow conduction, were tested in more detail as reference compounds. In isolated Purkinje fibres, flecainide largely slowed conduction and markedly increased triangulation, while lidocaine slightly slowed conduction and did not produce significant triangulation. Also in isolated left ventricular wedge preparations, flecainide largely slowed conduction in a rate-dependent manner, and elicited ventricular tachycardia (VT). Lidocaine slightly slowed conduction, reduced Tp-Te and did not induce VT. Similarly in isolated hearts, flecainide markedly slowed conduction, increased Tp-Te and elicited VT or ventricular fibrillation (VF). The slowing of conduction and induction of VT/VF with flecainide was much more evident in a condition of ischaemia/reperfusion. Lidocaine abolished ischaemia/reperfusion-induced VT/VF. Flecainide blocked sodium current (I(Na)) preferentially in the activated state (i.e. open channel) with slow binding and dissociation rates in a use-dependent manner, and lidocaine weakly blocked I(Na).

CONCLUSION AND IMPLICATIONS

Slowing conduction by blocking I(Na) could be potentially pro-arrhythmic. It is possible to differentiate between compounds with 'good' (lidocaine-like) and 'bad' (flecainide-like) I(Na) blocking activities in these models.

Decrease in density of INa is in the common final pathway to heart block in murine hearts overexpressing calcineurin

Overexpression of calcineurin in transgenic mouse heart results in massive cardiac hypertrophy followed by sudden death. Sudden deaths are caused by abrupt transitions from sinus rhythm to heart block (asystole) in calcineurin-overexpressing (CN) mice. Preliminary studies showed decreased maximum change in potential over time (d V/d tmax) of phase 0 of the action potential. Accordingly, the hypothesis was tested that decreased activity of the sodium channel contributes to heart block. Profound decreases in activity of sodium currents ( INa) paralleled the changes in action potential characteristics. Progressive age-dependent decreases were observed such that at 42–50 days of life little sodium channel function existed. However, this was not paralleled by decreased protein expression as assessed by immunocytochemistry or by Western blot. Since calcineurin can interact with the ryanodine receptor, we assessed whether chronic in vitro treatment with BAPTA-AM, thapsigargin, and ryanodine could rescue the decrease of INa. All of these treatments rescued INa to levels indistinguishable from wild type. The nonspecific PKC inhibitor bisindolylmaleimide I also rescued the decrease of INa. To assess whether decreased sodium channel activity contributes to sudden death in vivo, the response to encainide (20 mg/kg) was assessed: 6 of 10 young CN mice died because of asystole, whereas 0 of 10 wild-type mice died ( P < 0.01). Moreover, encainide produced exaggerated prolongation of the QRS width in sinus beats before the heart block. Catecholamine tone appears necessary to support life in older CN mice because propranolol (1 mg/kg) triggered asystolic death in five of six CN mice. We conclude that decrease in sodium channel activity is in the common final pathway to asystole in CN mice.

Actions of flecainide on susceptibility to phase-2 ventricular arrhythmias during infarct evolution in rat isolated perfused hearts

The mechanism of flecainide-induced unexpected death remains uncertain. Phase-2 ventricular arrhythmias occur during infarct evolution. We examined whether flecainide (0.74 and 1.48 microM, representing the peak unbound plasma and total blood concentrations, respectively, at 'therapeutic' dosage) has proarrhythmic activity on phase-2 arrhythmia susceptibility during infarct evolution. To achieve this, we used the Langendorff-perfused rat heart preparation (n=8 per group) in which baseline phase-2 arrhythmia susceptibility is low. Left main coronary occlusion evoked phase-1 (acute ischaemia-induced) ventricular arrhythmias including fibrillation (VF) in all hearts. By 90 min, hearts were relatively arrhythmia-free. Randomized and blinded switch of perfusion to flecainide at 90 min caused no increase over baseline in the incidence of VF, tachycardia (VT) or premature beats (VPB) during the following 150 min of ischaemia, or during reperfusion (begun 240 min after the onset of ischaemia). In separate hearts, catecholamines (313 nM norepinephrine and 75 nM epinephrine) were co-perfused with flecainide from 90 min of ischaemia. Catecholamine perfusion increased heart rate, coronary flow and QT interval, and shortened PR interval (all P<0.05), actions that were not altered by flecainide. Catecholamine perfusion caused a weak nonsignificant increase in phase-2 VPB, VT and VF incidence, but there was no proarrhythmic interaction with flecainide. In conclusion, the present findings suggest that the increased risk of death associated with clinical use of flecainide is not due to facilitation of phase-2 ventricular arrhythmias.

Antidepressant therapy in patients with ischemic heart disease

Depressive disorders are common in patients with ischemic heart disease and have serious consequences in terms of the risk of further cardiac events and cardiac mortality. Among survivors of acute myocardial infarction, up to one fifth meet diagnostic criteria for major depression, and the presence of major depression carries a >5-fold increased risk for cardiac mortality within 6 months. This article reviews clinical trial data on the cardiac safety profiles of antidepressant agents with the aim of discussing clinical considerations in selecting the most appropriate treatment of comorbid depression in patients with ischemic heart disease. Tricyclic antidepressants are effective against depression but are associated with cardiovascular side effects including orthostatic hypotension, slowed cardiac conduction, antiarrhythmic activity, and increased heart rate. Selective serotonin reuptake inhibitors, by contrast, have benign cardiovascular profiles and are well tolerated in patients with cardiac disease. The safety of dual-acting serotonin and noradrenaline reuptake inhibitors has not been well studied. Intervention with a selective serotonin reuptake inhibitors has the potential to provide the depressed patient with ischemic heart disease relief from their depressive symptoms and may offer a potential improvement in their cardiovascular risk profile.

Phase 2 ventricular arrhythmias in acute myocardial infarction: a neglected target for therapeutic antiarrhythmic drug development and for safety pharmacology evaluation

Ventricular fibrillation (VF), a cause of sudden cardiac death (SCD) in the setting of acute myocardial infarction (MI), remains a major therapeutic challenge. In humans, VF may occur within minutes or hours after the onset of chest pain, so its precise timing in relation to the onset of ischaemia is variable. Moreover, because VF usually occurs unobserved, out of hospital, and is usually lethal in the absence of intervention, its precise timing of onset is actually unknown in most patients. In animal models, the timing of susceptibility to VF is much better characterised. It occurs in two distinct phases. Early VF (defined as phase 1 VF, with possible subphases 1a and 1b in some animal species) occurs during the first 30 min of ischaemia when most myocardial injury is still reversible. Late VF, defined as phase 2 VF, occurs when myocardial necrosis is becoming established (after more than 90 min of ischaemia). Although much is known about the mechanisms and pharmacology of phase 1 VF, little is known about phase 2 VF. By reviewing a range of different types of data we have outlined the likely mechanisms and clinical relevance of phase 2 VF, and have evaluated possible future directions to help evolve a strategy for its suppression by drugs. The possibility that a proarrhythmic effect on phase 2 VF contributes to the adverse cardiac effects of certain cardiac and noncardiac drugs is also discussed in relation to the emerging field of safety pharmacology. It is concluded that suppression of phase 2 as well as phase 1 VF will almost certainly be necessary if drugs of the future are to achieve what drugs of the past and present have failed to achieve: full protection against SCD. Likewise, safety will require avoidance of exacerbation of phase 2 as well as phase 1 VF.

Phobic anxiety and risk of coronary heart disease and sudden cardiac death among women

BACKGROUND

High levels of phobic anxiety have been associated with elevated risks of coronary heart disease (CHD) death and sudden cardiac death (SCD) among men. To the best of our knowledge, no studies have looked at this association among women. Anxiety may influence CHD mortality by increasing the risk of ventricular arrhythmia and SCD.

METHODS AND RESULTS

We prospectively examined the relationship between phobic anxiety, as measured by the Crown-Crisp index (CCI), and CHD among women participating in the Nurses' Health Study. Among 72,359 women with no history of cardiovascular disease or cancer in 1988, 97 SCDs, 267 CHD deaths, and 930 nonfatal myocardial infarctions (MI) were documented over 12 years of follow-up. A higher score on the CCI was associated with an increased risk of SCD and fatal CHD but not of nonfatal MI in age-adjusted (P, trend < or =0.008) and in multivariable models excluding possible biological intermediaries (P, trend < or =0.03). Multivariable adjustment appeared to attenuate the relations; women who scored 4 or greater on the CCI were at a 1.59-fold (95% CI, 0.97 to 2.60) marginally increased risk of SCD and a 1.31-fold (95% CI, 0.97 to 1.75) marginally increased risk of fatal CHD compared with those who scored 0 or 1. After control for possible intermediaries (hypertension, diabetes, and elevated cholesterol), a trend toward an increased risk persisted for SCD (P=0.06).

CONCLUSIONS

These prospective data suggest that high levels of phobic anxiety are associated with an increased risk of fatal CHD, particularly from SCD. Some but not all of this risk can be accounted for by CHD risk factors associated with phobic anxiety.

Pharmacologic treatment of depression in patients with heart disease

The relationship between depression and cardiovascular disease is complex and multifaceted. There is a growing body of evidence that depression significantly and adversely affects cardiovascular health. Perhaps the most prominent finding is the documented increase in mortality rate in patients with depression after myocardial infarction. The critical questions of interest to both the clinician and researcher are whether there are safe and effective treatments for depression in patients with heart disease and whether treatment of depression reduces the increased risk of cardiac morbidity and mortality. Although the data are limited and are primarily from open or comparator trials, the tricyclics (TCAs) and selective serotonin reuptake inhibitors (SSRI) are effective for treatment of depression in patients with ischemic heart disease (IHD), and response rates are comparable with those reported in depressed patients without heart disease. In terms of safety, the TCAs are associated with documented adverse cardiovascular effects, including increases in heart rate, orthostatic hypotension, and conduction delays. Use of TCAs in patients with IHD carries a proven increased risk of cardiac morbidity and perhaps of mortality as well. The SSRI appear to be relatively safe and effective in the treatment for depression in patients with comorbid IHD.

Myocardial electrical alteration in canine preparations with combined chronic rapid pacing and progressive coronary artery occlusion

Our objective was to create an animal preparation displaying long-term electrical alterations after chronic regional energetic stress without myocardial scarring. An Ameroid (AM) constrictor was implanted around the left circumflex coronary artery (LCx) 2 wk before chronic rapid ventricular pacing (CRP) was initiated at 240 beats/min for 4 wk (CRP-AM). Comparisons were made with healthy canines and canines with either AM or CRP. Unipolar electrograms were recorded from 191 sites in the LCx territory in open-chest, anesthetized animals during sinus rhythm and while pacing at 120–150 beats/min, with bouts of transient rapid pacing (TRP; 240/min). In CRP-AM and AM, ST segment elevation was identified at central sites and ST depression at peripheral sites, both increasing with TRP. In CRP-AM and CRP, the maximum negative slope of unipolar activation complexes was significantly depressed and activation-recovery intervals prolonged. Areas of inexcitability as well as irregular isocontour patterns displaying localized activation-recovery intervals shortening and gradients >20 ms between neighboring sites were identified in one-third of CRP-AM at slow rate, with increasing incidence and magnitude in response to TRP. In CRP-AM, programmed stimulation-induced marked conduction delay and block as well as polymorphic ventricular tachycardias, which stabilized into monomorphic tachycardias with the use of lidocaine or procainamide. Whole cell Na+ current and channel protein expression were reduced in CRP-AM and CRP. Despite complete constrictor closure, small areas of necrosis were detected in a minority of CRP-AM. Long-term electrical alterations and their exacerbation by TRP contribute to arrhythmia formation in collateral-dependent myocardium subjected to chronic tachycardic stress.

Neither vasopressin nor amiodarone improve CPR outcome in an animal model of hypothermic cardiac arrest

BACKGROUND

Aim of this experimental animal study was to investigate the influence of vasopressin and amiodarone on cardiopulmonary resuscitation (CPR) outcome in a pig model of hypothermic cardiac arrest.

METHODS

After surface cooling to a core temperature of 26 degrees C, ventricular fibrillation was induced in 14 12-16-week-old domestic pigs. After 15 min of untreated cardiac arrest, a manual closed chest CPR was started and pigs were randomly assigned to two treatment groups: Group 1 pigs (n = 7) received vasopressin 0.4 U kg-1 as initial drug therapy, followed by a combination vasopressin (0.4 U kg-1) and amiodarone (4 mg kg-1) as subsequent drug therapy. Subsequent drug therapy was administered in animals without permanent restoration of spontaneous circulation after a first series of electrical countershocks 10 min after drug administration. Group 2 pigs (n = 7) received saline placebo as initial drug therapy and saline placebo and amiodarone (4 mg kg-1) as subsequent drug therapy.

RESULTS

Vasopressin significantly increased coronary perfusion pressure and defibrillation success (successful defibrillation in five of seven Group 1 vs. none of seven Group 2 pigs, P = 0.02). Due to refibrillation within 30-150 s, the 60-min survival rate was not improved by vasopressin. Subsequent drug therapy with amiodarone had no further effect on defibrillation success or the refibrillation rate.

CONCLUSIONS

Data from this experimental animal model suggest that vasopressin and amiodarone may not be beneficial for treatment of ventricular fibrillation associated with severe hypothermia when concomitant measures at core rewarming are not applied.

Treatment of depression in patients with heart disease

There is a growing body of evidence that depression significantly and adversely affects cardiovascular health. Perhaps the most prominent finding is the documented increase in mortality rate in patients with depression after myocardial infarction. The critical questions of interest to both the clinician and researcher are whether there are safe and effective treatments for depression in patients with heart disease and whether treatment of depression reduces the increased risk of cardiac morbidity and mortality. Though the data are limited and are primarily from open or comparator trials, the tricyclic antidepressants (TCAs), selective serotonin reuptake inhibitors (SSRIs), and specific psychotherapies appear to be effective for treatment of depression in patients with ischemic heart disease (IHD), and response rates are comparable to those reported in depressed patients without heart disease; however, there has been only one placebo-controlled trial to date, and therefore it is premature to come to definitive conclusions regarding the efficacy of antidepressant therapies in this patient population. With respect to safety, the TCAs are associated with documented adverse cardiovascular effects, including increases in heart rate, orthostatic hypotension, and conduction delays. Use of TCAs in patients with IHD carries a proven increased risk of cardiac morbidity and perhaps of mortality as well. The SSRIs appear to be relatively safe and effective treatment for depression in patients with comorbid IHD.

Toxicologic myocardial sensitization

Drug-induced polymorphic ventricular tachycardia (torsades de pointes) may lead to syncope or sudden cardiac death. One mechanism by which drugs and toxins may predispose to the development of this malignant dysrhythmia is through their ability to produce myocardial sensitization. The concept of myocardial sensitization actually represents a series of events involving altered cellular repolarization produced by blockade of myocardial potassium channels. Altered potassium ion flow raises the likelihood that an ectopic beat will occur via an early afterdepolarization and simultaneously alters the myocardial tissue to make it favorable for reentrant dysrhythmias, such as torsades de pointes, to propagate. Alternatively, calcium overload of the myocyte produces ectopy by causing delayed afterdepolarizations, which if the substrate for reentry is present, will result in ventricular tachycardia. This paper discusses the mechanisms underlying the production of both the altered myocardial substrate and the afterdepolarizations.