A CD&D

It has been fairly common to say that a shock with an automated external cardioverter (AED) must be given to someone experience cardiac arrest within a 10-minute window following initial attack.

But while defibrillation within that 10-minute window may save the person’s life, if the shock comes after the first two minutes of that window, it may not be soon enough to prevent significant mental impairment. This realization has served to shrink the therapeutic window — for both life-saving shock and continued mental well-being — to the first two minutes following cardiac arrest onset.

And it is naturally assumed that the hospital may be the venue most likely to provide shock within that two-minute window.

Not so, says a recent study.

Hospitalized patients are too often not receiving that early, necessary defibrillation, according to results of a study conducted by a team from the Mid-America Heart Institute of St. Luke’s Hospital (Kansas City, Missouri) and the University of Michigan Cardiovascular Center (Ann Arbor).

An estimated 750,000 hospitalized patients experience cardiac arrest and undergo CPR annually, and less than 30% of those leave the hospital alive.

In a paper published in the Jan. 3 issue of the New England Journal of Medicine, researchers quantified the impact of defibrillation provided as therapy to hospitalized patients experiencing ventricular arrhythmia.

Their finding? — that the chances of survival for hospitalized patients improve dramatically if defibrillation is administered within the expert-recommended two minute timeframe.

Using an analysis of data from the National Registry of Cardiopulmonary Resuscitation, the authors concluded that 30% of patients with cardiac arrest due to ventricular arrhythmia received life-saving defibrillation more than two minutes after initial recognition of their cardiac arrest, a delay thus exceeding the guidelines-based recommendations.

The delayed defibrillation was linked to a significantly lower probability of survival to hospital discharge — 22% vs. 39% when defibrillation wasn’t delayed.

Additionally, their data found that there was a 26% lower likelihood among survivors of being discharged without major neurological impairment.

“While several prior studies have shown an association between defibrillation time and survival, these were relatively small studies that typically included patients whose arrest rhythms would not have benefited from defibrillation” said lead study author Paul Chan, MD, a cardiologist and researcher from St. Luke’s Mid America Heart Institute. Chan was previously with the University of Michigan, where he initiated the study with University of Michigan cardiologist Brahmajee Nallamothu, MD, the paper’s senior author.

The study used a larger, more statistically significant registry of nearly 7,000 patients and focused exclusively on appropriate patients with ventricular arrhythmia.

“We found that delayed defibrillation was common, and that rapid defibrillation was associated with sizable survival gains in these high-risk patients,” said Chan.

“However, the real work has yet to be done in this field. We now have to develop systems of care within the hospital to improve defibrillation times nationally.”

The researchers said the next step is to do studies to identify the hospital policies, practices, equipment and personnel that ensure defibrillation therapy in less than two minutes following cardiac arrest.