Delayed Defibrillation Linked To Lower Heart Attack Survival In Hospital

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Main Category: Cardiovascular / Cardiology
Also Included In: Medical Devices / Diagnostics;  Neurology / Neuroscience
Article Date: 03 Jan 2008 - 3:00 PDT

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A new American study found that delayed defibrillation is common and is linked to lower survival rates of patients who have a heart attack while in hospital. Patients who received the procedure within the recommended 2 minutes of a heart attack had a significantly higher rate of survival.

The study is the work of Dr Paul S. Chan, a cardiologist and researcher with Saint Luke's Mid-America Heart Institute, Kansas City, Missouri, and colleagues. It is published in the January 3rd issue of the New England Journal of Medicine (NEJM).

It is estimated that three quarters of a million Americans have a heart attack in hospital, and that more than 70 per cent of them don't survive.

Although experts advise defibrillation (giving a life saving electric shock to the heart) should take place within two minutes of a heart attack (cardiac arrest) there is little evidence of the extent to which this procedure is delayed in US hospitals and how its delay affects survival.

As Chan explained:

"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."

In this study, Chen and colleagues looked at data on 6,789 patients who had cardiac arrest as a result of ventricular fibrillation or pulseless ventricular tachycardia. The patients were based at 369 hospitals that were part of the National Registry of Cardiopulmonary Resuscitation.

Ventricular fibrillation and tachycardia occur when different chambers or ventricles of the heart either beat out of sync with each other or pump too fast, resulting in partial or severe lack of oxygen in the bloodstream or complete disruption of heart function and no effective cardiac output.

Using a statistical method called logistic regression analysis, the researchers looked for clusters of variables linked to delayed defibrillation, and then looked for patterns linking delayed defibrillation (more than 2 minutes) and survival (up to the point of discharge).

The results showed that:

• Overall median time to defibrillation was 1 minute, ranging from less than one minute to three minutes.


• 30 per cent of patients received delayed defibrillation (2,045 patients).


• Characteristics linked to delayed defibrillation included: being black, being admitted with a non cardiac diagnosis, having a heart attack in a small hospital (fewer than 250 beds), being in an unmonitored hospital unit, and having a heart attack after normal working hours (between 5 pm and 8 am or at weekends).


• Patients who received delayed defibrillation had the lowest chance of leaving the hospital alive (22.2 per cent versus 39.3 per cent for those who received it within 2 minutes).


• There was also a significant decline in survival rate to discharge for each extra minute of delay.


• Survivors who received defibrillation within the recommended 2 minutes also had a 26 percent lower likelihood of being discharged without major neurological impairment.

The authors concluded that:

"Delayed defibrillation is common and is associated with lower rates of survival after in-hospital cardiac arrest."

Chan said that:

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

"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," he urged.

Co-author Dr Brahmajee Nallamothu who is a cardiologist at the University of Michigan (where Chan was last posted) explained that the study presented an opportunity to improve patient care, and:

"We need to understand how delayed defibrillation, which was more common after-hours and in unmonitored settings, relates to the immediate availability of medical personnel or equipment, as well as potential delays in recognition of ventricular arrhythmia."

"Delayed Time to Defibrillation after In-Hospital Cardiac Arrest."
Chan, Paul S, Krumholz, Harlan M, Nichol, Graham, Nallamothu, Brahmajee K, the American Heart Association National Registry of Cardiopulmonary Resuscitation Investigators.
N Engl J Med 2008 358: 9-17.
Volume 358, pages 9-17, January 3, 2008, Number 1

Click here for Abstract.

Sources: University of Michigan Health System press release, NEJM article.

Written by: Catharine Paddock
Copyright: Medical News Today
Not to be reproduced without permission of Medical News Today

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