ICD use contributes to decline in cardiac arrest

By Piriya Mahendra, MedWire Reporter

Implantable cardioverter defibrillator (ICD) use is responsible for one-third of the decline in cardiac arrests caused by ventricular fibrillation (VF), researchers say.

Rudolph Koster (University of Amsterdam, the Netherlands) and team found that between 2005 and 2008 in North Holland, 1972 ICD patients received 977 shocks. Of these shocks, 339 were caused by a life-threatening arrhythmia.

Using the assumption that a life-threatening arrhythmia leads to an emergency medical service (EMS) call in 62% of cases and a subsequent resuscitation effort for VF out-of-hospital cardiac arrest (OHCA) in 67% of cases, the researchers estimate that the 339 appropriate ICD shocks prevented 81 cases of presumed VF OHCA.

This amounts to an incidence rate of 1.2 per 100,000 person-years in 2005-2008. The authors say in Circulation that because the VF OHCA incidence declined by 3.6 per 100,000 person-years from 1995-1997 to 2005-2008, ICD usage therefore accounted for 33% of this decline.

The study also showed that the percentage of patients with VF OHCA fell significantly from 63% in 1995-1997 to 47% in 2005-2008.

However, the incidence rate of cardiac arrest related to other abnormal rhythms increased significantly, from 12.2 per 100,000 person-years to 19.4 per 100,000 person-years annually.

Koster says it is unclear what caused the other two-thirds of the decline in VF arrests between 1995 and 2008, or why cardiac arrest due to other abnormal rhythms has increased over this time. "The possible mechanisms are only guesses without much solid evidence," he remarked in a press statement.

He said it is likely other Western countries that implant ICDs for VF have also seen a decline in OHCA.

The researchers used data from the Amsterdam Resuscitation Studies registry of cardiac resuscitations by EMS between 1995 and 1997, and EMS cardiac arrest interventions in the greater Amsterdam area between 2005 and 2008.

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