Which of the following drugs has both a treatment and diagnostic role in narrow complex tachycardias?

c. Adenosine is a naturally occurring purine nucleoside with a pharmacological half-life of less than 2 seconds. Its principal role is in the diagnosis and management of paroxysmal supraventricular tachycardia. Cautions include atrial fibrillation or flutter caused by accessory pathways and contraindications include second- or third-degree heart block and sick sinus syndrome. Before administering adenosine to a patient it is important to tell them that they may experience a strange sensation that may lead them to feel like they are about to die. This sensation may last for a few seconds.

Atenolol is a beta-blocker and has limited use in an acute setting whilst atorvastatin has a role in reduction of cholesterol in a chronic capacity. Amlodipine is a calcium channel blocker and amiodarone has a role in refractory ventricular fibrillation or atrial flutter.