<s>[INST] context: Here in the question vital are unstable. so best therapy will be DC cardioversion Normal qRS complex = 0.08-0.1 sec. Prolonged QRS suggestive of: 1. Atrial fibrillation with ventricular pre-excitation (AVN) 2. Ventricular tachycardia Diagnostic criteria for ventricular tachycardia are: Presence of qRS duration >140 ms in the absence of drug therapy. Superior and rightward qRS frontal plane axis, Bizarre qRS complex that does not mimic the characteristic qRS pattern associated with left or right bundle branch block Slurring of the initial poion of the qRS Hence the pt. is not having Ventricular Tachycardia. In patients who manifest pre-excitation and AF--> therapy should be aimed at preventing a rapid ventricular response. In life-threatening situations, DC cardioversion should be used to terminate the AF. Vagal stimulation with the Valsalva maneuver and carotid sinus pressure may create sufficient AV nodal slowing to terminate the AV. Intravenous administration of adenosine, 6-12 mg, is first-line pharmacologic therapy; the calcium channel blockers verapamil and diltiazem or beta blockers may also be effective. [/INST] question: A 40-year-old lady intraoperatively develops HR = 220 bpm and Blood pressure of 70/40, ECG shows qRS complex =120 milliseconds. What is the best management? | options: A: Adenosine 6 mg/12 mg B: Amiodarone C: DC cardioversion D: Esmolol | answer: C </s>