Are antiarrhythmic agents indicated in premature ventricular complex-induced cardiomyopathy and when?

INTRODUCTION

Premature ventricular complexes (PVCs) are the most common ventricular arrhythmia that are encountered in the clinical practice. Recent data suggests that high PVC burden may lead to the development of PVC-induced cardiomyopathy (PVC-CM) even in patients without structural heart disease. Treatment for effective suppression of PVCs, can reverse PVC-CM. Both antiarrhythmic drugs (AADs) and catheter ablation (CA) are recognized treatment modalities for any cardiac arrhythmias. However, with increasing preference of CA, the role of AADs needs further defining regarding their efficacy, safety, indications and patient selection to treat PVC-CM.

METHODS

To ascertain the role of AADs to treat PVC-CM; whether they are indicated to treat PVC-CM, and if so, when, we interrogated PubMed and other search engines for English language publications with key words premature ventricular complexes (PVCs), cardiomyopathy, anti-arrhythmic drugs, catheter ablation, and pharmacological agents. All publications were carefully reviewed and scrutinized by the authors for their inclusion in the review paper. For illustration of cases, ethical standard was observed as per the 1975 Declaration of Helsinki, and the patient was treated as per the prevailing standard of care. Informed consent was obtained from the patient for conducting the ablation procedure.

RESULTS

Our literature search specifically the pharmacological treatment of PVC-CM with AADs revealed significant paradigm shift in treatment approach for PVCs and PVC-induced cardiomyopathy. No major large, randomized control trials of AADs versus CA for PVC-CM were found. We found that beta-blockers and calcium channel blockers are particularly effective in the treatment of PVCs originating from right ventricular outflow tract. For Class Ic AADs - flecainide and propafenone, small clinical studies showed Class Ic AADs to be effective in PVC suppression, but their usage was not recommended in patients with significant coronary artery disease. Mexiletine was found to have modest effect on PVC suppression. Studies showed sotalol to significantly reduce PVCs frequency in patients receiving both low and high doses. Studies also showed amiodarone to have higher successful PVC suppression, but not recommended as a first-line treatment for patients with idiopathic PVCs in the absence of symptoms and left ventricular dysfunction. For dronedarone, no major clinical data were available.

CONCLUSIONS

Based on the available data in the literature, we conclude that AADs play important role in the treatment of PVC-induced cardiomyopathy. However, appropriate patient selection criteria are vitally important, and in general terms AADs are indicated or polymorphic PVCs, epicardial PVCs; and when CA procedure is contraindicated, or not feasible or failed.

Atrial Fibrillation: Rate Versus Rhythm Control

Description Atrial fibrillation (AF) remains the most common arrhythmia worldwide and is expected to affect approximately 12 million individuals in the United States alone by 2030. Thromboembolic events remain a feared complication of AF and should be treated and risk-stratified utilizing the CHA2DS2-VASc scoring system. Other complications of AF span a wide spectrum from impaired quality of life (QoL) to an increase in all-cause mortality. Rate control strategies consist of controlling the ventricular rate and have been shown to be a safe and effective strategy for asymptomatic AF patients. In patients who are plagued with symptoms leading to impaired QoL or a decrease in exercise capacity, rhythm control with antiarrhythmic drugs or catheter ablation may be suitable options. Mortality benefits when comparing rate versus rhythm control remain equivocal when comparing multiple studies over the past decade.

Effectiveness of Catheter Ablation in Left Ventricular Ejection Fraction, Stroke, Quality of Life, All-Cause Mortality, Sinus Rhythm Maintenance, and Hospitalization Rates as Compared to Medical Therapy

Atrial fibrillation (AF) in the setting of heart failure (HF) accounts for a significant proportion of mortality. AF can be managed either with rate control or rhythm control strategies. Rate control involves the use of beta blockers or calcium channel blockers. Rhythm control methods use antiarrhythmic drugs or catheter ablation (CA) to abolish the rhythm. Articles from PubMed and Google Scholar were chosen for review. The literature was reviewed for data from the last 10 years to be chosen for interpretation. Clinical trials, meta-analyses, and systematic analysis were included in this study. Various health parameters such as all-cause mortality, hospitalization rates, sinus rhythm (SR) maintenance, quality of life improvement, stroke risk, left ventricular ejection fraction (LVEF) improvement, and healthcare costs were analyzed. We demonstrated that CA was superior to medical therapy in reducing all-cause mortality and hospitalization. It leads to significant improvement in LVEF as SR was maintained consistently. Overall, quality of life improved in those who underwent ablation as compared to those who did not. Stroke risk reduction was seen in observational studies only. We recommend CA as first-line therapy for treating patients with AF in the setting of HF. More clinical trials are needed to determine the effectiveness of ablation in reducing stroke risk.

High-Dose Oral Amiodarone for Cardioversion of Atrial Fibrillation: A Case Report

With the rising prevalence of atrial fibrillation (AF), it has become a global health problem with increasing complications and high medical costs. Here, we describe the case of a 52-year-old woman with chest discomfort and frequent palpitations for the last few months. A careful clinical and instrumental examination showed that the patient had AF. Sinus rhythm was restored by cardioversion using high-dose oral amiodarone therapy. Although this medication can be an alternative with several advantages over electrical cardioversion in the future, further studies are needed to establish its efficacy and safety profile.

Moving in the right direction: elucidating the mechanisms of interaction between flecainide and the cardiac ryanodine receptor

Flecainide is used to treat catecholaminergic polymorphic ventricular tachycardia (CPVT), an arrhythmia caused by disrupted cellular Ca²⁺ handling following β-adrenergic stimulation. The clinical efficacy of flecainide in this context involves complex effects on multiple ion channels that may be influenced by the disease state. A compelling narrative has been constructed around flecainide's nonselective block of sarcoplasmic reticulum (SR) lumen-to-cytoplasm Ca²⁺ release through intracellular calcium release channels (RyR2). However, ion fluxes across the SR membrane during heart contraction are bidirectional, and here, we review experimental evidence that flecainide's principal action on RyR2 involves the partial block of ion flow in the cytoplasm-to-lumen direction (i.e., flecainide inhibits RyR2-mediated SR 'countercurrent'). Experimental approaches that could advance new knowledge on the mechanism of RyR2 block by flecainide are proposed. Some impediments to progress in this area, that must be overcome to enable the development of superior drugs to treat CPVT, are also considered.

Review of the 2020 ESC Guidelines for the Diagnosis and Management of Atrial Fibrillation-What Has Changed and How Does This Affect Daily Practice

The high prevalence of atrial fibrillation (AF) in the overall population and its association with substantial morbidity, increased mortality and health care cost has instigated significant basic and clinical research efforts over recent years. The publication of multiple new high-quality randomized multi-center trials in the area of AF management and the rapidly evolving technological progress in terms of diagnostic possibilities and catheter ablation in recent years demanded a revision of the previous ESC AF Guidelines from 2016. The 2020 guidelines provide up-to-date, evidence-based guidance for the management of AF. One of the most important innovations is the presentation of a new concept for structural characterization of AF (the “4S AF scheme”) replacing the traditional classification based on its temporal pattern alone (paroxysmal-persistent-permanent). The 4S-AF-scheme highlights the importance of systematic assessment of stroke risk, severity of symptoms, total AF burden and underlying substrate as the foundation for effective and individualized AF treatment for each and every patient. Further novelties relate to the presentation of an easy and intuitive management pathway (“ABC pathway”) and strengthening the recommendations for early rhythm control, in particular the role of first line catheter ablation in heart failure. Another core component of the guidelines is the focus on patient involvement to achieve optimal outcomes. Patient education, shared decision making and incorporation of patient values and patient reported outcome of treatment interventions as well as integrated care by a multidisciplinary team all have a central role in the proposed management pathway for AF.

Variation of Two S3b Residues in KV4.1-4.3 Channels Underlies Their Different Modulations by Spider Toxin κ-LhTx-1

The naturally occurred peptide toxins from animal venoms are valuable pharmacological tools in exploring the structure-function relationships of ion channels. Herein we have identified the peptide toxin κ-LhTx-1 from the venom of spider Pandercetes sp (the Lichen huntsman spider) as a novel selective antagonist of the K_V4 family potassium channels. κ-LhTx-1 is a gating-modifier toxin impeded K_V4 channels' voltage sensor activation, and mutation analysis has confirmed its binding site on channels' S3b region. Interestingly, κ-LhTx-1 differently modulated the gating of K_V4 channels, as revealed by toxin inhibiting K_V4.2/4.3 with much more stronger voltage-dependence than that for K_V4.1. We proposed that κ-LhTx-1 trapped the voltage sensor of K_V4.1 in a much more stable resting state than that for K_V4.2/4.3 and further explored the underlying mechanism. Swapping the non-conserved S3b segments between K_V4.1(₂₈₀FVPK₂₈₃) and K_V4.3(₂₇₅VMTN₂₇₈) fully reversed their voltage-dependence phenotypes in inhibition by κ-LhTx-1, and intensive mutation analysis has identified P282 in K_V4.1, D281 in K_V4.2 and N278 in K_V4.3 being the key residues. Furthermore, the last two residues in this segment of each K_V4 channel (P282/K283 in K_V4.1, T280/D281 in K_V4.2 and T277/N278 in K_V4.3) likely worked synergistically as revealed by our combinatorial mutations analysis. The present study has clarified the molecular basis in K_V4 channels for their different modulations by κ-LhTx-1, which have advanced our understanding on K_V4 channels' structure features. Moreover, κ-LhTx-1 might be useful in developing anti-arrhythmic drugs given its high affinity, high selectivity and unique action mode in interacting with the K_V4.2/4.3 channels.

Catheter Ablation vs. Anti-Arrhythmic Drugs as First-Line Treatment in Symptomatic Paroxysmal Atrial Fibrillation: A Systematic Review and Meta-Analysis of Randomized Clinical Trials

Background: Catheter ablation has become a well-established indication for long-term rhythm control in atrial fibrillation (AF) patients refractory to anti-arrhythmic drugs (AADs). Efficacy and safety of AF catheter ablation (AFCA) before AADs failure are, instead, questioned. Objective: The aim of the study was to perform a systematic review and meta-analysis of randomized clinical trials (RCTs) comparing first-line AFCA with AADs in symptomatic patients with paroxysmal AF. Methods: We performed a random-effects meta-analysis of binary outcome events comparing AFCA with AADs in rhythm control-naïve patients. The primary outcomes, also stratified by the type of ablation energy (radiofrequency or cryoenergy), were (1) recurrence of atrial tachyarrhythmias and (2) recurrence of symptomatic atrial tachyarrhythmias. The secondary outcomes included adverse events. Results: Six RCTs were included in the analysis. AFCA was associated with lower recurrences of atrial tachyarrhythmias [relative risk (RR) 0.58, 95% confidence interval (CI) 0.46-0.72], consistent across the two types of ablation energy (radiofrequency, RR 0.50, 95% CI 0.28-0.89; cryoenergy, RR 0.60, 95% CI 0.50-0.72; p-value for subgroup differences: 0.55). Similarly, AFCA was related to less symptomatic arrhythmic recurrences (RR 0.46, 95% CI 0.27-0.79). Overall, adverse events did not differ. A trend toward increased periprocedural cardiac tamponade or phrenic nerve palsy was observed in the AFCA group, while more atrial flutter episodes with 1:1 atrioventricular conduction and syncopal events were reported in the AAD group. Conclusions: First-line rhythm control therapy with AFCA, independent from the adopted energy source (radiofrequency or cryoenergy), reduces long-term arrhythmic recurrences in patients with symptomatic paroxysmal AF compared with AADs.

Targeting of Potassium Channels in Cardiac Arrhythmias

Cardiomyocytes are endowed with a complex repertoire of ion channels, responsible for the generation of action potentials (APs), travelling waves of electrical excitation, propagating throughout the heart and leading to cardiac contractions. Cardiac AP waveforms are shaped by a striking diversity of K⁺ channels. The pivotal role of K⁺ channels in cardiac health and disease is underscored by the dramatic impact that K⁺ channel dysfunction has on cardiac arrhythmias. The development of drugs targeted to specific K⁺ channels is expected to provide an optimized approach to antiarrhythmic therapy. Here, we review the functional roles of cardiac potassium channels under normal and diseased states. We survey current antiarrhythmic drugs (AADs) targeted to voltage-gated and Ca²⁺-activated K⁺ channels and highlight future research opportunities.

Current Drug Treatment Strategies for Atrial Fibrillation and TASK-1 Inhibition as an Emerging Novel Therapy Option

Atrial fibrillation (AF) is the most common sustained arrhythmia with a prevalence of up to 4% and an upwards trend due to demographic changes. It is associated with an increase in mortality and stroke incidences. While stroke risk can be significantly reduced through anticoagulant therapy, adequate treatment of other AF related symptoms remains an unmet medical need in many cases. Two main treatment strategies are available: rate control that modulates ventricular heart rate and prevents tachymyopathy as well as rhythm control that aims to restore and sustain sinus rhythm. Rate control can be achieved through drugs or ablation of the atrioventricular node, rendering the patient pacemaker-dependent. For rhythm control electrical cardioversion and pharmacological cardioversion can be used. While electrical cardioversion requires fasting and sedation of the patient, antiarrhythmic drugs have other limitations. Most antiarrhythmic drugs carry a risk for pro-arrhythmic effects and are contraindicated in patients with structural heart diseases. Furthermore, catheter ablation of pulmonary veins can be performed with its risk of intraprocedural complications and varying success. In recent years TASK-1 has been introduced as a new target for AF therapy. Upregulation of TASK-1 in AF patients contributes to prolongation of the action potential duration. In a porcine model of AF, TASK-1 inhibition by gene therapy or pharmacological compounds induced cardioversion to sinus rhythm. The DOxapram Conversion TO Sinus rhythm (DOCTOS)-Trial will reveal whether doxapram, a potent TASK-1 inhibitor, can be used for acute cardioversion of persistent and paroxysmal AF in patients, potentially leading to a new treatment option for AF.

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.

Treatment of Older Patients with Atrial Fibrillation by Morbidity Burden

AIMS

Older patients with atrial fibrillation (AF) are at risk of adverse outcomes, which is accentuated by comorbidities. We sought to examine the association between morbidity burden and the treatment of older AF patients.

METHODS AND RESULTS

Using Danish nationwide registers we included patients ≥ 70 years of age between 2010 and 2017 at their first hospitalization due to AF. Using multiple logistic regression models we examined the association between morbidity burden and the odds of receiving oral anticoagulants (OACs), anti-arrhythmic drugs (AAD), and rhythm control procedures (direct current cardioversions and catheter ablations).A total of 48,995 patients were included with a majority of women (54%), with a median age of 80 years (interquartile range [IQR] 75-85), and a median morbidity burden of 2 comorbidities (IQR 1-3). Increasing morbidity burden was associated with decreasing odds of OAC treatment with patients having > 5 comorbidities having the lowest odds (Odds Ratio [OR] 0.38, 95% Confidence Interval [CI] 0.35-0.42) compared to patients with low morbidity burden (0-1 comorbidities). Having > 5 comorbidities was associated with increased odds of AAD treatment (OR 1.90, 95% CI 1.64-2.21) and decreased odds of AF procedures (OR 0.39, 95% CI 0.31-0.48), compared to patients with a low morbidity burden (0-1 comorbidities). Examining morbidity burden continuously revealed similar results.

CONCLUSIONS

In older AF patients, multimorbidity was associated with lower odds of receiving OACs and rhythm control procedures but increased odds of AADs. This presents a clinical conundrum as multimorbid patients potentially benefit the most from treatment with OACs.

Vernakalant hydrochloride for the treatment of atrial fibrillation: evaluation of its place in clinical practice

Vernakalant is an intravenous anti-arrhythmic drug available in Europe, Canada and some countries in Asia for the restoration of sinus rhythm in acute onset atrial fibrillation. Currently, it is not available in USA because the US FDA have ongoing concerns about its safety. Vernakalant has a unique pharmacological profile of multi-ion channel activity and atrial-specificity that distinguishes it from other anti-arrhythmic drugs. This is thought to enhance efficacy but there are concerns of adverse events stemming from its diverse pharmacology. This ambiguity has prompted a review of the available clinical evidence on efficacy and safety to help re-evaluate its place in clinical practice.

Mechanisms of Action of the KCa2-Negative Modulator AP30663, a Novel Compound in Development for Treatment of Atrial Fibrillation in Man

Aims

Small conductance Ca²⁺-activated K⁺ channels (SK channels, K_Ca2) are a new target for treatment of atrial fibrillation (AF). AP30663 is a small molecule inhibitor of K_Ca2 channels that is currently in clinical development for treatment of AF. The aim of this study is to present the electrophysiological profile and mechanism of action of AP30663 and its efficacy in prolonging atrial refractoriness in rodents, and by bioinformatic analysis investigate if genetic variants in KCNN2 or KCNN3 influence the expression level of these in human heart tissue.

Methods and Results

Whole-cell and inside-out patch-clamp recordings of heterologously expressed K_Ca2 channels revealed that AP30663 inhibits K_Ca2 channels with minor effects on other relevant cardiac ion channels. AP30663 modulates the K_Ca2.3 channel by right-shifting the Ca²⁺-activation curve. In isolated guinea pig hearts AP30663 significantly prolonged the atrial effective refractory period (AERP) with minor effects on the QT-interval corrected for heart rate. Similarly, in anaesthetized rats 5 and 10 mg/kg of AP30663 changed the AERP to 130.7±5.4% and 189.9±18.6 of baseline values. The expression quantitative trait loci analyses revealed that the genome wide association studies for AF SNP rs13376333 in KCNN3 is associated with increased mRNA expression of KCNN3 in human atrial appendage tissue.

Conclusions

AP30663 is a novel negative allosteric modulator of K_Ca2 channels that concentration-dependently prolonged rodent atrial refractoriness with minor effects on the QT-interval. Moreover, AF associated SNPs in KCNN3 influence KCNN3 mRNA expression in human atrial tissue. These properties support continued development of AP30663 for treatment of AF in man.

Rate or Rhythm Control in Older Atrial Fibrillation Patients: Risk of Fall-Related Injuries and Syncope

OBJECTIVES

Management of atrial fibrillation (AF) with rate and/or rhythm control could lead to fall-related injuries and syncope, especially in the older AF population. We aimed to determine the association of rate and/or rhythm control with fall-related injuries and syncope in a real-world older AF cohort.

DESIGN

A retrospective cohort study.

SETTING

Danish nationwide administrative registries from 2000 to 2015.

PARTICIPANTS

A total of 100 935 patients with AF aged 65 years or older claiming prescription of rate-lowering drugs (RLDs) and/or anti-arrhythmic drugs (AADs) were included. We compared the use of rate-lowering monotherapy with rate-lowering dual therapy, AAD monotherapy, and AAD combined with rate-lowering therapy.

MEASUREMENTS

Outcomes were fall-related injuries and syncope as a composite end point (primary) or separate end point (secondary).

RESULTS

In this population, the median age was 78 years (interquartile range [IQR] = 72-84 y), and 53 481 (53.0%) were women. During a median follow-up of 2.1 years (IQR = 1.0-5.1), 17 132 (17.0%) experienced a fall-related injury, 5745 (5.7%) had a syncope, and 21 093 (20.9%) experienced either. Compared with rate-lowering monotherapy, AADs were associated with a higher risk of fall-related injuries and syncope. The incidence rate ratio (IRR) for the composite end point was 1.29 (95% confidence interval [CI]: 1.17-1.43) for AAD monotherapy and 1.46 [95% CI = 1.34-1.58] for AAD combined with rate-lowering therapy. When stratifying by individual drugs, amiodarone significantly increased the risk of fall-related injuries and syncope (IRR = 1.40 [1.26-1.55]). Compared with more than 180 days of rate-lowering monotherapy, a higher risk of all outcomes was seen in the first 90 days of any treatment; however, the greatest risk was in the first 14 days for those treated with AADs.

CONCLUSION

In AF patients aged 65 years and older, AAD use was associated with a higher risk of fall-related injuries and syncope, and the risk was highest within the first 14 days for those treated with AADs. Only amiodarone use was associated with a higher risk. J Am Geriatr Soc 67:2023-2030, 2019.

Ion Channel Targeted Mechanisms of Anti-arrhythmic Chinese Herbal Medicine Xin Su Ning

Xin Su Ning (XSN) is a China patented and certified herbal medicine used to treat premature ventricular contractions (PVCs) since 2005. A recent completed clinical trial of 861 patients showed that XSN had similar PVC inhibition rate to the class I antiarrhythmic drug mexiletine, at 65.85% for XSN and 63.10% for mexiletine. We have previously reported that XSN prolongs action potential duration (APD) and suppresses action potential amplitude (APA) of the cardiac ventricular myocytes. In this report we aim to reveal the effect of XSN on the ionic channels that govern APD and APA, which would help to explain the cellular electrophysiological mechanism of XSN. Our main findings are: (1) On ECG recorded in isolated rat, in the presence of XSN the amplitude of R wave was significantly decreased and the amplitude of T wave was increased significantly; (2) XSN blocked hNaV1.5 channel stably transfected cell line in a dose-dependent manner with an IC₅₀ of 0.18 ± 0.02 g/L; and (3) XSN suppresses hERG channels in a dose-dependent manner with an IC₅₀ of 0.34 ± 0.01 g/L. In conclusion, the clinical antiarrhythmic efficacy of XSN is based on its class I and Class III antiarrhythmic properties by suppression hNaV1.5 channel and hERG channels, which are directly responsible for XSN’s effect on APA suppression and APD prolongation.

PAR1 contribution in acute electrophysiological properties of oral anticoagulants in rabbit pulmonary vein sleeve preparations

Whether oral anticoagulants, vitamin K antagonists (VKAs), and nonvitamin K oral anticoagulant (NOACs) frequently prescribed to atrial fibrillation (AF) patients, do themselves have a pro- or anti-arrhythmic effect have never been addressed. Transmembrane action potentials were recorded in an acute rabbit model of superfused pulmonary veins (PVs) sleeves preparations using standard microelectrode technique. Fluindione 10 μm (n = 6) increased the AP (action potential) duration (APD), induced a significantly V_max depression (from 95 ± 14 to 53 ± 5 V/s, P < 0.05), and 2 : 1 blocks during rapid atrial pacing thus evoking class I anti-arrhythmic properties, and prevented spontaneous trigger APs. Apixaban 10 μm (n = 6) increased the APD, significantly prolonged the effective refractory period (from 56.3 ± 4.2 to 72.0 ± 8.6 ms, P < 0.05), and prevented triggered APs occurrence. Fluindione and apixaban effects were suppressed with the addition of the protease-activated receptors 1 (PAR 1) agonist SFLLR-NH₂ . Warfarin 10 μm (n = 6) significantly abbreviated the early refractory period (from 56.3 ± 4.2 to 45.0 ± 2.2 ms, P < 0.05) and increased triggered APs occurrence that were successfully prevented by nifedipine but not by the addition of the protease-activated receptors 1 agonist SFLLR-NH₂ . In this acute rabbit PVs model, VKAs and NOACs, at physiological concentrations, exhibited very different pharmacological properties that influence PVs electrophysiology, implying PAR1, with fluindione and apixaban which exhibited more anti-arrhythmic properties, whereas warfarin exhibited more pro-arrhythmic properties.

Team Management of the Ventricular Tachycardia Patient

Ventricular tachycardia is a common arrhythmia in patients with structural heart disease and heart failure, and is now seen more frequently as these patients survive longer with modern therapies. In addition, these patients often have multiple comorbidities. While anti-arrhythmic drug therapy, implantable cardioverter-defibrillator implantation and ventricular tachycardia ablation are the mainstay of therapy, well managed by the cardiac electrophysiologist, there are many other facets in the care of these patients, such as heart failure management, treatment of comorbidities and anaesthetic interventions, where the expertise of other specialists is essential for optimal patient care. A coordinated team approach is therefore essential to achieve the best possible outcomes for these complex patients.

Pharmacokinetics and electrophysiological effects of sotalol hydrochloride in horses

BACKGROUND

Arrhythmias in horses may require long-term anti-arrhythmic therapy. Unfortunately, oral anti-arrhythmic drugs for use in horses are currently scarce. In human patients and small animals, sotalol, a β-blocker with class III anti-arrhythmic properties, is often used for long-term treatment.

OBJECTIVES

To determine the pharmacokinetics of sotalol at multiple oral dosages in unfasted horses, as well as the effects on electro- and echocardiographic measurements, right atrial and ventricular monophasic action potential (MAP) and effective refractory period (ERP).

STUDY DESIGN

Placebo controlled, double-blinded experiment.

MATERIALS AND METHODS

Six healthy, unfasted Warmblood horses were given either 0, 2, 3 or 4 mg/kg bodyweight (bwt) sotalol orally (PO) twice daily (bid) for 9 days in a randomised cross-over design. Echocardiography and surface electrocardiography were performed and plasma concentrations of sotalol and right atrial and right ventricular MAPs and ERPs were determined at steady-state conditions. Statistical analysis was performed using a repeated measures univariate analysis with post hoc Bonferroni corrections.

RESULTS

Calculated mean steady-state plasma concentrations determined by nonlinear mixed-effect modelling were 287 (range 234-339), 409 (359-458) and 543 (439-646) ng/mL for 2, 3 and 4 mg/kg bwt sotalol PO bid respectively. Sotalol significantly increased the QT interval and ERPs, but, despite increasing plasma concentrations, higher dosages did not result in a progressive increase in QT interval or ERPs. Echocardiographic and other electrocardiographic measurements did not change significantly. MAP durations at 90% repolarisation were not significantly different during sotalol treatment. Besides transient local sweating, no side effects were noted.

MAIN LIMITATIONS

Study size and ad libitum feeding of hay.

CONCLUSIONS

Sotalol at a dose of 2, 3 and 4 mg/kg bwt PO bid increases the QT interval and ERP and might be a useful drug for long-term anti-arrhythmic therapy in horses.

Pharmacological Therapy of Tachyarrhythmias During Pregnancy

Tachyarrhythmias are the most frequently observed cardiac complications during pregnancy. The majority of these maternal and foetal arrhythmias are supraventricular tachyarrhythmias; ventricular tachyarrhythmias are rare. The use of anti-arrhythmic drugs (AADs) during pregnancy is challenging due to potential foetal teratogenic effects. Maintaining stable and effective therapeutic maternal drug levels is difficult due to haemodynamic and metabolic alterations. Pharmacological treatment of tachyarrhythmias is indicated in case of maternal haemodynamic instability or hydrops fetalis. Evidenc e regarding the efficacy and safety of AAD therapy during pregnancy is scarce and the choice of AAD should be based on individual risk assessments for both mother and foetus. This review outlines the current knowledge on the development of tachyarrhythmias during pregnancy, the indications for and considerations of pharmacological treatment and its potential side-effects.

Arrhythmias in the developing heart

Prevalence of cardiac arrhythmias increases gradually with age; however, specific rhythm disturbances can appear even prior to birth and markedly affect foetal development. Relatively little is known about these disorders, chiefly because of their relative rarity and difficulty in diagnosis. In this review, we cover the most common forms found in human pathology, specifically congenital heart block, pre-excitation, extrasystoles and long QT syndrome. In addition, we cover pertinent literature data from prenatal animal models, providing a glimpse into pathogenesis of arrhythmias and possible strategies for treatment.

Intravenous vernakalant for the rapid conversion of recent onset atrial fibrillation: systematic review and meta-analysis

Atrial fibrillation is the most common cardiac arrhythmia and is associated with increased mortality and morbidity. Conversion to sinus rhythm is usually appropriate in patients with acute, symptomatic atrial fibrillation in order to reduce symptoms and prevent complications. Electrical cardioversion is the most used and widespread technique, but requires deep sedation and a fasting state. Pharmacological alternatives are burdened by a delayed onset of action and potential proarrhythmic effects. Therefore, new therapeutic options are being sought. Among those, vernakalant, showed a good efficacy profile and a short onset of action, but with conflicting evidence regarding potential serious adverse events. This drug profile will summarize the pharmacology behind this new drug and review recent evidence in terms of safety and efficacy.

Severity of obstructive sleep apnea influences the effect of genotype on response to anti-arrhythmic drug therapy for atrial fibrillation

STUDY OBJECTIVES

To examine the impact of genotype on the relationship between obstructive sleep apnea (OSA) and anti-arrhythmic drug (AAD) efficacy in atrial fibrillation (AF).

DESIGN

Registry based.

SETTING

Clinic-based.

PARTICIPANTS

Eighty-four individuals from Vanderbilt AF registry who had polysomnography, genotyping, and serial comprehensive evaluations of AF status.

INTERVENTIONS

None.

MEASUREMENTS AND RESULTS

Response to AADs was defined as a decrease in AF burden score by ≥ 75% or the combination of sinus rhythm on follow-up EKGs, stable AAD therapy for at least 6 months, objective AF burden below an established threshold, and the absence of non-pharmacologic therapies. Participants were genotyped for common AF susceptibility alleles at chromosomes 4q25 (near PITX2), 16q22 (in ZFHX3), and 1q21 (in KCNN3), and common SNPs in the β1-adrenergic receptor (ARDB1). Wild-type status for rs10033464 at 4q25 was associated with increased success of AAD therapy in patients with no or mild OSA (odds ratio: 10.0, 95% confidence interval: 1.03 to 97.5; p < 0.05), but did not influence response to AAD therapy in those with moderate-severe OSA. A similar trend was observed for rs1801252 on ARDB1.

CONCLUSION

In this hypothesis-generating pilot study of predominantly Caucasian men, the effect on AF response to AAD therapy of rs10033464 at 4q25 varied based on OSA status. The impact of genotype on AAD efficacy may be greatest in mild OSA and attenuated in more severe disease.