Background Information: Refractory ventricular fibrillation (RVF) is a complication of cardiac arrest defined as ventricular fibrillation (VF) that does not respond to three or more standard defibrillation attempts.1,2 Patients with RVF during their cardiac arrest have a mortality of up to 97%.3,4 Double external defibrillation (DED) involves the use of a second defibrillator providing an additional shock in a sequential or simultaneous manner. The left ventricle (LV), being the most posterior part of the heart and the furthest away from the anterolateral electrode pads, have led some to hypothesize that utilizing an anterior-posterior pad placement (ie. Changing the vector) is what accounts for DED’s success. Some theorize that the increase in amount of energy from two defibrillations as opposed to one is what’s needed to reach the LV. There are also theories suggesting that the sequential administration of the shocks, more effectively lowers the defibrillation threshold of the cardiac myocytes and thus leads to a more successful conversion of VF. In spite of these many theories, the intervention of DED has been studied for decades in the electrophysiology lab and widely discussed in the literature through case reports and meta-reviews. These case reports have shown success and a recent meta-review of 39 patients who received DED showed that 25% of them were discharged neurologically intact with Cerebral Performance Category (CPC) scores of 2 or less indicating normal recovery/mild disability or moderate disability but able to independently perform activities of daily living.5-10 While this literature is promising, DED is a highly variable intervention and there are still many unknown factors which continue to cause debate and controversy. The role of vector direction via pad placement, the role of a pulse interval in energy deliverance and the efficacy in method of delivering DED sequentially vs simultaneously continues to remain unclear. 6-11 The authors of this pilot RCT (DOSE VF) wished to answer some of these questions by first determining the feasibility and safety of performing a full RCT. In doing so, they used alternate defibrillation strategies such as vector changes and double external sequential defibrillation (DSED) in treating RVF.12...Read More
Background: Welcome back to the September 2016 REBEL Cast. We are back with another episode and I am super excited about this episode because we are going to talk about two papers just published in the Resuscitation Journal on management of refractory ventricular fibrillation. It is a well known fact that the cornerstones for survival from Out-Of-Hospital Cardiac Arrest (OHCA) have always been early, high quality CPR and early defibrillation in patients with shockable rhythms (i.e. Ventricular Fibrillation/Ventricular Tachycardia). Some patients with shockable rhythms may be refractory to standard defibrillation therapy (i.e. refractory VF). Even more frustrating, there is truly a dearth of data on what to do with these patients. One strategy that has been reported more and more in the literature is double sequential defibrillation (DSD).
Another issue in cardiac arrest patients is we frequently give boluses of 1mg epinephrine every 3 – 5 minutes as is outlined in the ACLS guidelines. When patients have minimal cardiac output, the buildup of catecholamines may potentially cause refractory ventricular fibrillation (RVF). This could be due to an increase myocardial oxygen consumption causing an increase in myocardial ischemia, and ultimately more difficulty in successful defibrillation. But maybe by blocking the beta-adrenergic receptors in the myocardium, we can block the beta effects of the catecholamines and potentially increase the chances of successful sustained ROSC.