Antiarrhythmic Drug Therapy for Atrial Fibrillation

Ethnic-Related Sodium Voltage-Gated Channel α Subunit 5 Polymorphisms Shape the In Vitro Pharmacological Action of Amiodarone upon Nav1.5

Nav1.5-derived Na+ current (INa) exerts a pivotal role in the depolarization phase of cardiomyocytes' action potential, and, therefore, changes in INa can contribute to fatal arrhythmias. Nav1.5 displays naturally occurring ethnicity-related polymorphisms, which might alter the functioning and pharmacology of the channel. Some studies have shown how single-nucleotide polymorphism can change the response to antiarrhythmic drugs. Investigations on the role of Nav1.5 in arrhythmogenesis associated with its functional polymorphisms are currently growing as well as the possible variability in the antiarrhythmic pharmacotherapy among ethnic groups. The influence of the ethnicity-related polymorphisms (S524Y, S1103Y, R1193Q, V1951L) on the responsiveness, selectivity, and pharmacological efficacy of the clinically used antiarrhythmic amiodarone (AMIO) is not completely known. Our objectives were to analyze biophysical and pharmacological aspects of four ethnicity-related polymorphisms before and after exposure to AMIO. Polymorphisms caused reduced AMIO potency compared with wild type (WT), which can vary by up to 4× between them. AMIO shifted the voltage dependency for current inactivation without significant effect in voltage-dependent activation to a similar extent in WT and polymorphisms. The recovery from inactivation was altered between the polymorphisms when compared with WT. Finally, the use dependency of AMIO differed between studied groups, especially at a more depolarized cell membrane. Thus, our work may guide future studies focusing on the efficiency of AMIO in treating different arrhythmias and establish more individualized guidelines for its use depending on the Nav1.5 polymorphism after validating our findings using in vivo studies. SIGNIFICANCE STATEMENT: Sodium voltage-gated channel α subunit 5 (SCN5A) gene encodes the α subunit of Nav1.5, the main cardiac voltage-gated Na+ channel. Interestingly, ethnicity-related polymorphisms are found in SCN5A. Amiodarone is used in clinical practice, and some of its effects are attributed to interaction with Nav1.5. Important, amiodarone efficacy is variable among patients. Here we show that ethnicity-related SCN5A polymorphisms lead to altered Nav1.5-amiodarone interaction, which may be the cause for the variable efficacy observed in clinical usage of amiodarone.

Emergency Department Management of Recent-Onset Atrial Fibrillation

Atrial fibrillation (AF) is the most common tachyarrhythmia managed in the emergency department (ED). Visits to the ED for a presentation of AF have been increasing in recent years, with an admission rate that exceeds 60% in the United States and contributes substantially to health care costs. Recent-onset AF-defined as symptom onset less than 48 hr-is a common ED presentation for which rate control or acute electrical or pharmacological cardioversion may be appropriate treatment modalities depending on patient-specific circumstances. The focus of this review is to discuss the current recommendations regarding the management of recent-onset nonvalvular AF in the ED, discuss medication administration considerations, and identify implementation strategies in the ED to optimize throughput and reduce hospital admissions.

Fluvastatin combined with benazepril may contribute to the favorable prognosis of patients with atrial fibrillation

The aim of this study was to observe the clinical efficacy of fluvastatin combined with benazepril in the treatment of patients with atrial fibrillation (AF). A total of 92 patients with AF were randomly assigned to the case group (n=46), in which the patients were treated with fluvastatin (80mg) plus benazepril (10mg), or to the control group (n=46), in which the patients were treated with fluvastatin (80mg). The conversion rate of sinus rhythm was higher in the case group than in the control group (P<0.05). The case group had more treatment-effective patients than the control group, with fewer treatment-ineffective patients (P<0.05). The LVEDd, LVESd, LAD, and LVEF indexes in the case group were lower than in the control group after 6 months of treatment (all P<0.05). Levels of hs-CRP were also lower in patients in the case group than in patients in the control group after 1 month of treatment (P<0.05). After 12 months, renin and Ang II concentrations were lower in patients in the case group than in the control group (both P<0.05). Significant differences in IL-6 and TNF-α expression were found between the two groups after 1 month, 6 months, and 12 months of treatment (all P<0.05). Compared to patients in the control group, the levels of total cholesterol (TC), triglycerides, and LDL-C in the case group were lower after 6 and 12 months of treatment (all P<0.05), while the HDL level was higher (P<0.05). Treatment with fluvastatin combined with benazepril further increased the conversion rate of sinus rhythm and significantly improved the quality of life and prognosis of AF patients.