Dofetilide: Electrophysiologic Effect, Efficacy, and Safety in Patients with Cardiac Arrhythmias

When the Clock Strikes A-fib

Within the broad spectrum of atrial fibrillation (AF) symptomatology, there is a striking subset of patients with predominant or even solitary nocturnal onset of the arrhythmia. This review covers AF with nocturnal onset, with the aim of defining this distinctive subgroup among patients with AF. A periodicity analysis is provided showing a clear increased onset between 10:00 pm and 7:00 am. Multiple interacting mechanisms are discussed, such as circadian modulation of electrophysiological properties, vagal tone, and sleep disorders, as well as the potential interaction and synergism between these factors, to provide a better understanding of this clinical entity. Lastly, potential therapeutic targets for AF with nocturnal onset are addressed such as upstream therapy for underlying comorbidities, type of drug and timing of drug administration and pulmonary vein isolation, ablation of the ganglionated plexus, and autonomic nervous system modulation. Understanding the underlying AF mechanisms in the individual patient with nocturnal onset will contribute to patient-specific therapy.

Clinical Characteristics of Atrial Flutter and Its Response to Pharmacological Cardioversion with Amiodarone in Comparison to Atrial Fibrillation

BACKGROUND

Unlike atrial fibrillation (AF), atrial flutter (AFl) is thought to be relatively refractory to pharmacological cardioversion (PC), but the evidence is scarce. The aim of this study was to evaluate the clinical characteristics and efficacy of the PC of AFl with amiodarone in comparison to AF.

MATERIALS AND METHODS

This retrospective study covered 727 patients with urgent consult for AF/AFl in a high-volume emergency department between 2015 and 2018. AFl was diagnosed in 222 (30.5%; median age: 68 (62; 75) years; 65.3% men). In a nested case-control study, 59 control patients with AF, matched in terms of age and sex with 60 AFl patients, were subject to PC with amiodarone. The primary endpoint was return of sinus rhythm confirmed using a 12-lead ECG.

RESULTS

The AFl population had a median CHA2DS2-VASc score of 3 (2; 4) and episode duration of 72 h (16; 120). In the AFl cohort, 36% of patients were initially subject to PC, 33.3% to electrical cardioversion (EC) and 40.5% to catheter ablation. In comparison to the AF group, the AFl patients required a longer hospitalization time, had a higher rate of EC (p < 0.001) and less frequent use of PC (p < 0.001) and, lower left ventricular ejection fraction (p < 0.001) and more pronounced cardiovascular risk factors. The efficacy of PC with amiodarone was significantly lower in AFl than AF group (39% vs. 65%, relative risk (RR) 0.60, p = 0.007).

CONCLUSIONS

AFl patients shared a greater burden of comorbidities than AF patients, while the efficacy of PC in AFl was low. Patients should be initially managed with primary electrical cardioversion.

Discovery of a brain-sparing GIRK1/4 inhibitor for pharmacological cardioversion of atrial fibrillation

Atrial fibrillation (AF) is the most common cardiac arrhythmia, and a significant risk factor for ischemic stroke and heart failure. Marketed anti-arrhythmic drugs can restore sinus rhythm, but with limited efficacy and significant toxicities, including potential to induce ventricular arrhythmia. Atrial-selective ion channel drugs are expected to restore and maintain sinus rhythm without risk of ventricular arrhythmia. One such atrial-selective channel target is GIRK1/4 (G-protein regulated inwardly rectifying potassium channel 1/4). Here we describe 14b, a potent GIRK1/4 inhibitor developed to cardiovert AF to sinus rhythm while minimizing central nervous system exposure - an issue with preceding GIRK1/4 clinical candidates.

Mitochondrial Effects of Common Cardiovascular Medications: The Good, the Bad and the Mixed

Mitochondria are central organelles in the homeostasis of the cardiovascular system via the integration of several physiological processes, such as ATP generation via oxidative phosphorylation, synthesis/exchange of metabolites, calcium sequestration, reactive oxygen species (ROS) production/buffering and control of cellular survival/death. Mitochondrial impairment has been widely recognized as a central pathomechanism of almost all cardiovascular diseases, rendering these organelles important therapeutic targets. Mitochondrial dysfunction has been reported to occur in the setting of drug-induced toxicity in several tissues and organs, including the heart. Members of the drug classes currently used in the therapeutics of cardiovascular pathologies have been reported to both support and undermine mitochondrial function. For the latter case, mitochondrial toxicity is the consequence of drug interference (direct or off-target effects) with mitochondrial respiration/energy conversion, DNA replication, ROS production and detoxification, cell death signaling and mitochondrial dynamics. The present narrative review aims to summarize the beneficial and deleterious mitochondrial effects of common cardiovascular medications as described in various experimental models and identify those for which evidence for both types of effects is available in the literature.

Antiarrhythmic Drug Therapy in the Treatment of Acute and Chronic Atrial Flutter

In the present article, we will focus on the pharmacologic treatment of atrial flutter aimed either at restoring/maintaining sinus rhythm or controlling the ventricular response during tachyarrhythmia. To provide a comprehensive description we will start discussing the electroanatomic substrate underlying the development of atrial flutter and the complex relationship with atrial fibrillation. We will then describe the available drugs for the treatment of atrial flutter on the bases of their electrophysiological effects and data from available clinical studies. We will conclude by discussing the general principles of rhythm and rate control treatment during atrial flutter.

MATE1 Deficiency Exacerbates Dofetilide-Induced Proarrhythmia

Dofetilide is a rapid delayed rectifier potassium current inhibitor widely used to prevent the recurrence of atrial fibrillation and flutter. The clinical use of this drug is associated with increases in QTc interval, which predispose patients to ventricular cardiac arrhythmias. The mechanisms involved in the disposition of dofetilide, including its movement in and out of cardiomyocytes, remain unknown. Using a xenobiotic transporter screen, we identified MATE1 (SLC47A1) as a transporter of dofetilide and found that genetic knockout or pharmacological inhibition of MATE1 in mice was associated with enhanced retention of dofetilide in cardiomyocytes and increased QTc prolongation. The urinary excretion of dofetilide was also dependent on the MATE1 genotype, and we found that this transport mechanism provides a mechanistic basis for previously recorded drug-drug interactions of dofetilide with various contraindicated drugs, including bictegravir, cimetidine, ketoconazole, and verapamil. The translational significance of these observations was examined with a physiologically-based pharmacokinetic model that adequately predicted the drug-drug interaction liabilities in humans. These findings support the thesis that MATE1 serves a conserved cardioprotective role by restricting excessive cellular accumulation and warrant caution against the concurrent administration of potent MATE1 inhibitors and cardiotoxic substrates with a narrow therapeutic window.

Management of atrial fibrillation: two decades of progress - a scientific statement from the European Cardiac Arrhythmia Society

BACKGROUND

Atrial fibrillation (AF) is the most common sustained arrhythmia encountered in clinical practice. The aim of this review was to evaluate the progress made in the management of AF over the two last decades.

RESULTS

Clinical classification of AF is usually based on the presence of symptoms, the duration of AF episodes and their possible recurrence over time, although incidental diagnosis is not uncommon. The majority of patients with AF have associated cardiovascular diseases and more recently the recognition of modifiable risk factors both cardiovascular and non-cardiovascular which should be considered in its management. Among AF-related complications, stroke and transient ischaemic accidents (TIAs) carry considerable morbidity and mortality risk. The use of implantable devices such as pacemakers and defibrillators, wearable garments and subcutaneous cardiac monitors with recording capabilities has enabled to access the burden of "subclinical AF". The recent introduction of non-vitamin K antagonists has led to improve the prevention of stroke and peripheral embolism. Agents capable of reversing non-vitamin K antagonists have also become available in case of clinically relevant major bleeding. Transcatheter closure of left atrial appendage represents an option for patients unable to take oral anticoagulation. When treating patients with AF, clinicians need to select the most suitable strategy, i.e. control of heart rate and/or restoration and maintenance of sinus rhythm. The studies comparing these two strategies have not shown differences in terms of mortality. If an AF episode is poorly tolerated from a haemodynamic standpoint, electrical cardioversion is indicated. Otherwise, restoration of sinus rhythm can be obtained using intravenous pharmacological cardioversion and oral class I or class III antiarrhythmic is used to prevent recurrences. During the last two decades after its introduction in daily practice, catheter ablation has gained considerable escalation in popularity. Progress has also been made in AF associated with heart failure with reduced or preserved ejection fraction.

CONCLUSIONS

Significant progress has been made within the past 2 decades both in the pharmacological and non-pharmacological managements of this cardiac arrhythmia.

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.

Dofetilide-Induced Microvolt T-Wave Alternans

Dofetilide is an antiarrhythmic drug that selectively inhibits the rapid component of the delayed rectifier potassium current. The administration of dofetilide may cause ventricular arrhythmias and torsade de pointes. Electrocardiographic (ECG) microvolt T-wave alternans (TWA), an electrophysiologic phenomenon consisting in the beat-to-beat alternation of the T-wave amplitude requiring computerized algorithms to be detected, has also been associated to malignant ventricular arrhythmias. Aim of the present study was to evaluate if dofetilide induces TWA during the 24 hours following administration. The study population consisted of 22 healthy subjects ("ECG Effects of Ranolazine, Dofetilide, Verapamil, and Quinidine in Healthy Subjects" database by Physionet) to whom a 500 μg-dose of dofetilide was administered. For each subject, 10 s ECG were acquired at baseline (0.5 hour before dofetilide administration) and at 15 time points during the 24 hours following the drug administration. ECG were then processed for automatic TWA detection by correlation method. In 21 subjects out of 22, after dofetilide administration, TWA significantly increased to a peak value (median TWA values went from 6 μV at baseline to a max 32 μV; p<; 0.05), on average after 5 hours, to then come back to values closer to baseline. Thus, in healthy subjects, dofetilide increases occurrence and levels (6 times baseline value on average) of TWA in the hours following its administration.

Development and validation of a UPLC-MS/MS analytical method for dofetilide in mouse plasma and urine, and its application to pharmacokinetic study

A novel method using UPLC with tandem mass-spectrometric detection (UPLC-MS/MS) with positive electrospray ionization was developed for the detection of the antiarrhythmic drug, dofetilide, in mouse plasma and urine. Protein precipitation was performed on 10 μL of plasma and 2 μL of urine samples using dofetilide-D4 as an internal standard, and separation of the analyte was accomplished on a C18 analytical column with the flow of 0.40 mL/min. Subsequently, the method was successfully applied to determine the pharmacokinetic parameters of dofetilide following oral and intravenous administration. The calibration curve was linear over the selected concentration range (R² ≥ 0.99), with a lower limit of quantitation of 5 ng/mL. The intra-day and inter-day precisions, and accuracies obtained from a 5-day validation ranged from 3.00 to 7.10%, 3.80-7.20%, and 93.0-106% for plasma, and 3.50-9.00%, 3.70-10.0%, 87.0-106% for urine, while the recovery of dofetilide was 93.7% and 97.4% in plasma and urine, respectively. The observed pharmacokinetic profiles revealed that absorption is the rate-limiting step in dofetilide distribution and elimination. Pharmacokinetic studies illustrate that the absolute bioavailability of dofetilide in the FVB strain mice is 34.5%. The current developed method allows for accurate and precise quantification of dofetilide in micro-volumes of plasma and urine, and was found to be suitable for supporting in vivo pharmacokinetic studies.

Pharmacist-Managed Inpatient Dofetilide Initiation Program: Description and Adherence Rate Post-Root Cause Analysis

The aim of this article is to describe the pharmacist-managed dofetilide initiation program at Maine Medical Center (MMC), assess the adherence rate to 8 core clinical metrics, and review adverse effects before and after a root cause analysis (RCA). Core clinical metrics included pharmacist note entered within 4 hours of dose administration, dose chosen correctly per renal function, QTc measurements obtained and reviewed 2 hours after each dose, appropriate dose adjustment per the most recent QTc measurement, documentation of patient education, and assessment of conduction abnormality, drug-drug interactions, and serum potassium and magnesium concentrations. The primary outcome was adherence rate to all 8 core clinical metrics before and after the RCA. The safety outcome was the total number of adverse events. One hundred patients undergoing elective dofetilide initiation were evaluated: 50 pre-RCA and 50 post-RCA. Adherence rate to all core metrics was 14% in the pre-RCA group and 44% in the post-RCA group (P < .001). Torsade de pointes occurred 3 times in the pre-RCA group and never in the post-RCA group. After the RCA, adherence to MMC's pharmacist-managed inpatient dofetilide initiation program significantly improved.