Eleutheroside B, a selective late sodium current inhibitor, suppresses atrial fibrillation induced by sea anemone toxin II in rabbit hearts

Eleutheroside B (EB) is the main active constituent derived from the Chinese herb Acanthopanax senticosus (AS) that has been reported to possess cardioprotective effects. In this study we investigated the effects of EB on cardiac electrophysiology and its suppression on atrial fibrillation (AF). Whole-cell recording was conducted in isolated rabbit atrial myocytes. The intracellular calcium ([Ca²⁺]_i) concentration was measured using calcium indicator Fura-2/AM fluorescence. Monophasic action potential (MAP) and electrocardiogram (ECG) synchronous recordings were conducted in Langendorff-perfused rabbit hearts using ECG signal sampling and analysis system. We showed that EB dose-dependently inhibited late sodium current (I_NaL), transient sodium current (I_NaT), and sea anemone toxin II (ATX II)-increased I_NaL with IC₅₀ values of 167, 1582, and 181 μM, respectively. On the other hand, EB (800 μM) did not affect L-type calcium current (I_CaL), inward rectifier potassium channel current (I_K), and action potential duration (APD). Furthermore, EB (300 μM) markedly decreased ATX II-prolonged the APD at 90% repolarization (APD₉₀) and eliminated ATX II-induced early afterdepolarizations (EADs), delayed afterdepolarizations (DADs), and triggered activities (TAs). Moreover, EB (200 μM) significantly suppressed ATX II-induced Na⁺-dependent [Ca²⁺]_i overload in atrial myocytes. In the Langendorff-perfused rabbit hearts, application of EB (200 μM) or TTX (2 μM) substantially decreased ATX II-induced incidences of atrial fibrillation (AF), ventricular fibrillation (VF), and heart death. These results suggest that augmented I_NaL alone is sufficient to induce AF, and EB exerts anti-AF actions mainly via blocking I_NaL, which put forward the basis of pharmacology for new clinical application of EB.

International variation in use of oral anticoagulation among heart failure patients with atrial fibrillation

BACKGROUND

We sought to characterize patient factors and regional variations associated with vitamin K antagonist (VKA) use in patients with heart failure (HF) and atrial fibrillation (AF) in areas outside the United States and Europe.

METHODS

The ADHERE-International registry enrolled patients with decompensated HF from 10 Asia Pacific and Latin American countries from December 2005 to January 2009. Rates of VKA use in patients with HF and either new-onset AF or a history of AF were determined and compared according to CHADS(2) scores. Multivariable logistic regression and hierarchical modeling with random effects for hospitals were used to determine clinical and regional factors associated with VKA use at discharge.

RESULTS

Among 9,706 admissions, there were 2,358 (24.3%) with prior AF and 674 (6.9%) with new-onset AF. The median age was 71 years (25th-75th percentiles 59-79) for prior AF and 69 (57-80) for new-onset AF patients. The overall rate of VKA use at discharge was 39.5%. Vitamin K antagonist use at discharge was 36.2% in patients with CHADS(2) scores ≥2 versus 50.2% in patients with CHADS(2) score equal to 1 (P < .0001). Vitamin K antagonist use was 36.4% in patients with hypertension, 28.1% in patients >75 years old, 34.8% in diabetics, and 44.4% in those with prior stroke/transient ischemic attack. After adjusting for patient characteristics, the highest and lowest rates of anticoagulation were in Australia (65.2%) and Taiwan (25.1%).

CONCLUSION

International use of guidelines-recommended anticoagulation in HF patients with AF varies significantly across countries and represents an important opportunity for improving quality of care.