Implantable cardioverter-defibrillators have reduced the incidence of resuscitation for out-of-hospital cardiac arrest caused by lethal arrhythmias

Background-Over the last decades, a gradual decrease in ventricular fibrillation (VF) as initial recorded rhythm during resuscitation for out-of-hospital cardiac arrest (OHCA) has been noted. We sought to establish the contribution of implantable cardioverter-defibrillator (ICD) therapy to this decline. Methods and Results-Using a prospective database of all OHCA resuscitation in the province North Holland in the Netherlands (Amsterdam Resuscitation Studies [ARREST]), we collected data on all patients in whom resuscitation for OHCA was attempted in 2005-2008. VF OHCA incidence (per 100 000 inhabitants per year) was compared with VF OHCA incidence data during 1995-1997, collected in a similar way. We also collected ICD interrogations of all ICD patients from North Holland and identified all appropriate ICD shocks in 2005-2008; we calculated the number of prevented VF OHCA episodes, considering that only part of the appropriate shocks would result in avoided resuscitation. VF OHCA incidence decreased from 21.1/100 000 in 1995-1997 to 17.4/100 000 in 2005-2008 (P<0.001). Non-VF OHCA increased from 12.2/100 000 to 19.4/100 000 (P<0.001). VF as presenting rhythm declined from 63% to 47%. In 2005-2008, 1972 ICD patients received 977 shocks. Of these shocks, 339 were caused by a life-threatening arrhythmia. We estimate that these 339 shocks have prevented 81 (minimum, 39; maximum, 152) cases of VF OHCA, corresponding with 33% (minimum, 16%; maximum, 63%) of the observed decline in VF OHCA incidence. Conclusions-The incidence of VF OHCA decreased over the last 10 years in North Holland. ICD therapy explained a decrease of 1.2/100 000 inhabitants per year, corresponding with 33% of the observed decline in VF OHCA.