Double Sequential (or Simultaneous?) Defibrillation for Refractory VF

The presence of sudden cardiac death is estimated to occur 300,000 to 350,000 annually with over 90% of such deaths as a results of ventricular fibrillation (VF). ACLS guidelines dictate that after addressing reversible causes or factors leading to the arrhythmia (hypoxia, electrolyte disturbances, mechanical factors, volume depletion), defibrillation should be performed with 360 J for monophasic defibrillators or 120-200 J for biphasic defibrillators. In a subset of patients, however, conventional means of terminating ventricular arrhythmias does not work. Energy requirements for refractory VF is controversial and, recently, the idea of double sequence defibrillation (DSD) has become a solution to refractory VF and subsequent death.

DSD is performed by attaching two sets of defibrillation pads rather than one and delivering two shocks as near simultaneously as possible, delivering electricity to the myocardial tissue in parallel pathways. The idea is that several factors affect the defibrillation threshold such as obesity, chronic lung disease, antiarrhythmic agents, decreased ejection fraction, body position/habitus, and presence of implanted internal defibrillator.

Hoch et al advocate for DSD in refractory VF. Hoch found that all five patients in the study converted to normal sinus rhythm after double sequence defibrillation at a total of 720 J. Other support for DSD come from the Cabanas paper, a retrospective case series which looked at 10 cases of refractory VF. In the paper, DSD successfully terminated 70% of refractory VF, attaining ROSC in 30% of those patients. Unfortunately, however, none of these patients survived to discharge. A contributing factor to explain the fact that there were no survivors to discharge was that DSD was performed too late. In the cases reviewed, 6.5 single shocks were given prior to DSD and in 6 of those cases, DSD was performed 35 minutes into resuscitation, which was probably too late.

           

Currently several systems around the world are using DSD for refractory VF.  Currently, we do not know the amount of joules to use for best survival. Nor do we know the correct number of pads or best pad vector. The risk/benefit profile seems very reasonable since all refractory VF leads to death. It is possible that we have finally figured out how to save these patients’ lives.

Anterior-Lateral/Anterior-Lateral

 Anterior-Lateral/Anterior-Posterior

References

1. Chang, Mau-Song et al. Double and Triple Sequential Shocks Reduce Ventricular Defibrillation Threshold in Dogs With and Without Myocardial Infarction. Journal of the American College of Cardiology 1986; 8 (6): 1393-1405.
2. Hoch, David H et al. Double Sequence External Shocks for Refractory Ventricular Fibrillation. JAC 1994; 23(5): 1141-1145.
3. Zipes, Douglas P et al. Management of Patients with Ventricular Arrhythmias and the Prevention of Sudden Cardiac Death. American Heart Association, American College of Cardiology Foundation 2006.
4. Pantridge, J. F et al. Electrical Requirements for Ventricular Defibrillation. British Medical Journal 1975; 2: 313-315.
5. Geddes, L. A. et al. Electrical Dose of Ventricular Defibrillation of Large and Small Animals Using Precordial Electrodes. Journal of Clinical Investigation 1974; 53(1): 310-319.
6. Adgey, A. A. J. Electrical energy requirements for ventricular defibrillation. British Heart Journal 1978; 40: 1197-1199.
7. Cabaas, J. G. Double sequence external defibrillation in out-of-hospital refractor ventricular fibrillation: a report of ten cases. Prehospital Emergency Care 2015; 19(1): 126-130.
8. Tacher, W. A. et al. Energy dosage for human trans-chest electrical ventricular defibrillation. New England Journal of Medicine 1974; 290: 214-215