The paramedics bring in a 60-year old male for witnessed cardiac arrest. CPR was started by by-standers, and the patient is still in an ongoing resuscitation. Airway is secured, standard ACLS protocol adhered, and on rhythm check, patient is in ventricular fibrillation. After multiple rounds of defibrillation, epinephrine, and amiodarone, patient’s rhythm stays the same. What do you do? Resuscitating cardiac-arrest patients is the bread-and-butter of emergency medicine, but when facing ventricular fibrillation (V-Fib) that is refractory to standard ACLS protocols and has mortality rate as high as 97%, a relatively new approach may be promising. Dual-sequence defibrillation (DSD) is the use of two defibrillators and two sets of defibrillator pads placed strategically to increase the energy and vector during defibrillation. Although not standard practice, it is done in refractory V-fib defined as persistent fibrillation after 3-5 defibrillation attempts, 3 rounds of 1mg epinephrine IV, and 300mg amiodarone IV at least once. Since a case-series from 1994 described five patients who were successfully converted out of V-Fib with DSD in electrophysiology lab settings, more case reports of successful DSD in refractory V-Fib in emergency room settings have been published. Some cases had favorable neurologic outcomes with minimal neurological deficits although several retrospective studies show unclear benefit in terms of mortality and morbidity. The goal of my presentation is to discuss current literature and findings regarding the pathophysiology in DSD, such as the timing theory, vector theory, and total energy theory. I will also discuss its indications, how it should be performed to optimize efficacy, pharmacologic agents that are coupled with DSD such as esmolol, and potential risks of this intervention. Most importantly, this should raise interest for a novel approach in cardiac-arrest resuscitation that still needs prospective studies.