Metoprolol Injection In The Treatment Of Rapid Atrial Arrhythmias In Clinical Studies

Part 1Efficacy of intravenous metoprolol in the treatment of atrialtachyarrhythmiasObjeetive To investigate the effectiveness and safety of intravenous (Ⅳ)metoprolol in the rapid ventricular rate control of atrial tachyarrhythmias.Methods 36 atrial tachyarrhythmic patients with a ventricular rate＞120beat per minute(bpm) were included and randomised to metoprolol groupor cedilanid group. Blood pressure and heart rate were measured at baseline (0min), before the second dose, before the third dose, 40, 60, 90, and120min after injection. The effective criteria was defined as decreasedventricular rate＜100 bpm or cardiovention to sinus rhythm.Results 36 patients (20 male,mean age 57.4±13.3 years) included 22cases of atrial fibrillation, 7 cases of atrial flutter and 7 cases of atrialtachycardia.20 patients were randomised to metoprolol group and 16patients to cedilanid group.The effective rate in the metoprolol group wassignificantly higher than that in the cedilanid group (45%,80%,90%,and90% versus 12.5%,18.8%,37.5%and 56.3%, respectively within 60minutes. P＜0.05). The mean interval of achieving effective rate formetoprolol and cedilanid was 13.1±7.6 min and 53.0±28.4 min,respectively (P＜0.01). The totally effective rate between two groups wasnot significantly different (90% in metoprolol group vs 75% in cedilanid group, P＞0.05).Conclusion Both metoprolol and cedilanid were effective and safe forthe management of rapid ventricular rate in atrial tachyarrhythmia.However, the ventricular rate control effect began much earlier withmetoprolol than with cedilanid. Part 2Evaluation of cardiac electrophysiologic effect by intravenousmetroprololObjective To investigate the cardiac electrophysiologic effect ofintravenous metroprololMethods 10 patients(male 9, female 1), average age 43.4±8.7 years,were studied. 10 patients had atriaoventricular reentrant tachycardia(AVRT)and had undergone radiofrequence cardiac ablationElectrophysiologic parameters and blood pressure were measured at baseline (0min) and at the point of 5 min and 15 min after metoprolol wasgiven.Results At 5 min and 15 min after metoprolol injection, sinus cyclelength(SCL),sinus node recovery time(SNRT),AH interval,atrioventricular node effective refractory period (AVNERP) andWenckebach cycle length of AVN were prolonged significantly. Therewere no significant changes of PA,HV, correct sinus node recovery time(cSNRT),right atrial effective refractory period (RAERP), rightventricular effective refractory period (RVERP).Conclusion Intravenous metroprolol could prolong AH interval andAVNERP;which may be the mechanism of treatment of supraventriculartachycardia.