Electrophysiologic Study Of The Effects Of Esmolol Hydrochloride

INTRODUCTION:Beta adrenergic blockers are widely used to treat supraventricular and ventricular tachycardias,hypertention,obstructive hypertrophic cardiomyopathy and coronary artery disease.However,the use of long-acting,non-cardioselective beta blockers are limited because of their adverse effects.such as bronchial spasm,hypotention.bradycardia and worsening of heart failure.Thus,short - acting beta blockers could be extreamly useful .since their actions are rapid in onset and offset.Esmolol is an ultra-short acting.cardioselective,beta-adrenergic blocking agent.lts distribution and elimination T1/2 averaged 2min and 9.2min,respectively.The rapid clinical onset and offset of action and the ability to titrate the drug to changing circumstances makes esmolol a useful addition to our treatment armamentarium.Esmolol is commonly used in supraventricular tachyarrhythmias,acute coronary artery syndrom.perioperative or intraoperative tachycardia , hypertension and myocardial ischemia, et al abroad presently.Esmolol is relatively safe in patients with bronchial spasm,hypotention.bradycardia or conduction block and heart failure.Similar to other beta blockers.the electrophysiologic effects of esmolol reported were on sinoatrial node and AV node.There was no direct effect on His - Purkinje or ventricular function. But there are disagreements on some aspects.such as the effects on sinus node recovery time, sinoatrial conduction time, atrial function. However,there isn't any research on the electrophysiologic effects of esmolol produced by our country yet.The clinical applications are also few.OBJECTIVE: To investigate the electrophysiologic characteristics and clinical applications of esmolol.METHODS: Twenty patients (aged 11 to 66 years) underwent diagnostic electrophysiologic studies at rest and during p-blockade induced wth esmolol.An initial loading dose of 500ug/Kg/min was infused for 5 minutes and followed by a maintainance infusion of 250ug/Kg/min that was continued until completion of the electrophysiologic measurements.The measurements were initiated at 5 minutes after termination of the infusion.The aderse effects were observed simultaneously.RESULTS: Esmolol significantly prolonged the sinus node recovery time(SNRT),atrial and atrioventricular nodal effective refractory periods (A-ERP & AVN-ERP),the atrioventricular Wenckebach cycle !ength(AVN-WCL) and A-H interval. Esmolol also produced a significantly reduction in heart rate(HR),diastolic and mean blood pressure(DBP&MBP)and rate-pressure product(RPP). However, esmolol did not influence the sinoatrial conduction time(SACT),P-A.A-H and H-V interval.ventricular effective refractoryperiod(V-ERP), systolicblood pressure(SBP) andelectrocardiographic(ECG) parameters(p>0.05).CONCLUSION: The electrophysiologic characteristics of esmololare similar to those reported abroad. Its major effects were on sinusnode and AV node function. Esmolol also showed no direct effects onHis-Purkinje or ventricular function.Esmolol decreased the heart rateand the myocardial oxygen demand.Esmolol,because of its ultrashortduration of action,could be safe and efficient in emergencytreatments.