Ajmaline, (also known by trade names Gilurytmal, Ritmos, and Aritmina) is an alkaloid found in the root of Rauwolfia serpentina, among other plant sources. It is a class Ia antiarrhythmic agent that apparently acts by changing the shape and threshold of cardiac action potentials. The class I antiarrhythmic agents interfere with the sodium channel. A class IA agent lengthens the action potential (right shift) which brings about improvement in abnormal heart rhythms. This drug in particular has a high affinity for the Nav 1.5 sodium channel. Ajmaline produces potent sodium channel blocking effects and a very short half-life which makes it a very useful drug for acute intravenous treatments. The drug has been very popular in some countries for the treatment of atrial fibrillation in patients with the Wolff–Parkinson–White syndrome and in well tolerated monomorphic ventricular tachycardias. It has also been used for many years as a drug to challenge the conduction system of the heart in cases of bundle branch block and syncope. In these cases, abnormal prolongation of the HV interval has been taken as a proof for infrahisian conduction defects tributary for permanent pacemaker implantation. Ajmaline is used as an antiarrhythmic agent.