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

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.