Question about Hemodynamic instability. Vagal maneuver and IV adenosine hints about PSVT/ AVN. And Pt. is refractory to Adenosine as max. dose is already given. So, next best step would be repeat adenosine according to new ACC guidelines, Only for those patients who are hemodynamically Stable > 90 mm Hg- brains tends to switch on auto regulation Question mentions about unstable patient therefore rules out repeat adenosine. Amiodarone -mainly used in treatment of broad complex VT - H/o AVN, narrow QRS complex Therefore rules out Amiodarone Defibrillation: Done for patient with ventricular fibrillation. It is basically a non-synchronized DC shock. It is given in: a. PVT Broad QRS b. Ventricular fibrillation Therefore, ruled out. Cardioversion is synchronized DC shock used for management of patients with any tachyarrhythmia for hemodynamic unstability. RR interval constant HR =300/min Narrow QRS Global ST segment depression in all leads Subendocardial ischemia, which is usually demonstrated in patients of PSVT. In both Harrisons and ACC guidelines