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Implantable defibrillators reduce cardiac arrests

Implantable cardioverter defibrillators (ICDs) account for one-third of the decrease in cardiac arrests caused by ventricular fibrillation (VF) in North-Holland, according to research published recently in Circulation.1

Researchers estimated that ICDs prevented 81 cardiac arrests during the 2005–2008 study, using data from the Amsterdam Resuscitation Studies registry of cardiac resuscitations by emergency medical services (EMS) in the greater Amsterdam area in 1995–1997, and all EMS cardiac arrest interventions in the area in 2005–2008.

To reach this estimate, they multiplied the number of life-threatening abnormal heart rhythms stopped by an ICD by the probability that the rhythm would have led to a call to EMS and a resuscitation attempt.

They assumed that a life-threatening abnormal heart rhythm would prompt calls to EMS in 62% of cases, and an attempt at resuscitation would occur in 67% of those people.

“At least one in 20 ICD carriers can expect a life-saving shock from their device each year,” said senior author Dr Rudolph W Koster (Academic Medical Center, Amsterdam).

Previous studies have shown a gradual 15-year decrease in VF-related cardiac arrests suffered outside the hospital setting – from 54% to 38% in the United States and Europe. However, the incidence of such cardiac arrests from other abnormal heart rhythms continues to increase each year.

Focusing on people known to have VF when EMS arrived, researchers found:

  • An estimated 339 shocks successfully stopped 194 instances of life-threatening abnormal heart rhythms in 166 people.
  • The percentage of patients with VF cardiac arrest fell from 63% in 1995–1997 to 47% in 2005–2008.
  • The annual incidence of VF cardiac arrests fell significantly, from 21.1 people per 100,000 to 17.4 people per 100,000.
  • Incidence of cardiac arrests related to other abnormal rhythms increased significantly, from 12.2 per 100,000 to 19.4 per 100,000 annually.

It’s unknown what caused the other two-thirds of decline in VF arrests or why cardiac arrests vs. other abnormal heart rhythms have increased.

“The possible mechanisms are only guesses without much solid evidence,” Dr Koster said.

It is likely that western countries that implant ICDs for similar indications would see a similar reduction in out-of-hospital cardiac arrest from ventricular fibrillation, he added.

References

1. Hulleman M, Berdowski J, de Groot JR, et al. Implantable cardioverter-defibrillators have reduced the incidence of resuscitation for out-of-hospital cardiac arrest caused by lethal arrhythmias. Circulation 2012;126:815–21. http://dx.doi.org/10.1161/​CIRCULATIONAHA.111.089425

Published on: August 24, 2012

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  • ArrhythmiaAlliance
  • Stars
  • Anticoagulation Europe
  • Atrial Fibrillation Association
 

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