<prompt> All of the following are seen in cardiac arrest except:Electromechanical dissociationAtrial fibrillationVentricular fibrillationVentricular tachycardia  <response>: Ans: b Atrial fibrillation Ref: Davidson, 20th ed, p. 555This is a direct pick from Davidson.Cardiac arrest may be due to ventricular fibrillation, ventricular tachycardia, electromechanical dissociation or ventricular asystole.Cause of cardiac arrest1 VF and pulseless VT -- Most common and most easily treatable cause of sudden death.2 Ventricular asystole -- This occurs when there is no electrical activity in the ventricles resulting in absent cardiac output.3 Electromechanical dissociation -- This occurs when there in no effective cardiac output despite the presence of normal electrical activity. 