The use of serum bepridil concentration as a safe rhythm control strategy in patients with atrial tachyarrhythmias

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The aim of this study was to evaluate the clinical significance of serum bepridil (Bep) concentration (SBC) for safely managing patients with atrial tachyarrhythmias (AT).
Methods and results: SBC was measured in 37 patients with AT, including atrial fribrillation (AF) (31 cases), AF+atrial flutter (AFL) (4 cases), AFL (1 case), and atrial tachycardia (1 case). The patients were administrated Bep for more than 4 weeks at the same dose. SBC was positively correlated with Bep dose per kilogram of body weight (p=0.015), QT interval (p=0.019), and QTc (p=0.034). The patients were divided into 2 groups according to their SBC: the high-SBC (HSBC) group of 8 patients with an SBC ≥500 ng/ml and a low-SBC (LSBC) group of 29 patients with an SBC <500 ng/ml. There was no difference in maintenance of sinus rhythm between the groups. For clinical variables, QT and QTc were significantly longer in the HSBC than in the LSBC group (p=0.004 and p=0.016, respectively). Patients with QT >0.5 were more prominent in the HSBC group (37.5% vs. 3.4%, p=0.026), and torsade de points (TdP) occurred in only one patient in the HSBC group. However, there were several patients with normal QT/QTc despite having high SBC.
Conclusions: In patients treated with Bep, measurement of SBC is useful for preventing proarrhythmias.