Defibrillation

Defibrillation refers to passing an electrical current across myocardium to depolarize the muscle in order to convert a dysrhythmia back into normal sinus rhythm. Defibrillation was first demonstrated in 1899. Application of defibrillation to convert VF into a perfusing rhythm occurred concurrently in multiple locations. The first successful use of an alternating-current internal defibrillator in a human was reported in 1947. The first successful use of an alternating-current external defibrillator on a human was reported in 1956. These defibrillators used energy from a landline (i.e., electricity from a wall socket). The first use of a portable direct-current external defibrillator (estimated weight: 3.2 kg) was reported in 1967. The first portable defibrillator in the United States was commercially available in 1968. Innovations have continued since the 1960s to produce smaller and lighter AEDS.⁴

The benefits of early defibrillation on survival and functional outcome though public-access defibrillation programs and greater accessibility and availability of AEDs in the community are unquestionable.¹ In a paper by Pollack et al. patients shocked by a bystander were significantly more likely to survive to discharge (66.5% vs. 43.0%) and be discharged with favourable functional outcome (57.1% vs. 32.7%) than patients initially shocked by emergency medical services.⁵

Defibrillation within 3–5 min of collapse can produce survival rates as high as 50–70%. Each minute of delay to defibrillation reduces the probability of survival to discharge by 10–12%. When bystander CPR is provided, the decline in survival is more gradual and averages 3–5% per minute delay to defibrillation.¹