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Positive Findings on Long-Term Neurological Outcome for Out-of-Hospital Cardiac Arrest

Moran, Mark

doi: 10.1097/01.NT.0000407222.44513.35
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A new study finds that cardiac arrest survivors had lower scores on measures of long-term memory and learning efficiency than did the general population, but nearly all were functionally independent and scored high on the Mini-Mental State Examination (MMSE) six months later.

Survival and long-term neurological outcome of patients having out-of-hospital cardiac arrest with ventricular fibrillation appeared to be good, according to a report that appears in the Sept. 14 online edition of Neurology. The results are encouraging, several experts not involved with the study pointed out, and point to positive advances in life-saving techniques. But one caveat, they noted, is that patients who survive cardiac arrest to hospital discharge and beyond typically have the least degree of brain injury of all arrest victims.

Survivors had lower scores on measures of long-term memory and learning efficiency than did the general population, but nearly all were functionally independent and scored high on the Mini-Mental State Examination (MMSE). Moreover, the survivors also scored higher than average on verbal IQ, according to the report.

The study is among the first to report cognitive outcomes years after cardiac arrest, with a median survival of 7.8 years, and the results reflect the advances accruing from rapid treatment of ventricular fibrillation and the success of “chain of survival” protocols.

“There has been some pessimism in neurology about long-term cognitive outcome, but existing studies have used very gross measures of outcome with maybe five or six points between dead and normal,” explained lead author Farrah J. Mateen, MD, a fellow in the department of neurology at Johns Hopkins University School of Medicine. “In our study we looked for specific deficits in cognition and memory, and overall our results are very encouraging.

“Survivors have a high functional status and the cognitive deficits they do experience are fairly minor,” she told Neurology Today.

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In the study, adults who experienced out-of-hospital cardiac arrest with ventricular fibrillation (OHCA VF) in Olmsted County, MN, from 1990 to 2008, who survived more than six months post-arrest, and who were alive at the time of study recruitment were invited to participate in structured neuropsychological testing and a neurological examination.

Of 332 OHCA VF arrests, 140 people survived to discharge and no patient entered a minimally conscious or permanent vegetative state. At the time of cardiac arrest, the patient's age, sex, time between 911 call and first defibrillation, and type of first responder were recorded. Patients were further categorized by whether the cardiac arrest was witnessed or unwitnessed and if a bystander performed CPR until a first responder arrived with an automated external defibrillator.

All patients were admitted to a single hospital, and variables recorded at the time of hospitalization included the final cardiac diagnosis, and overall performance category (OPC) score. Of 74 survivors still living (at the time of the study), 63 patients were invited to participate and 47 patients, with a median age of 67.4 years, completed the evaluation.

Scores from the Alzheimer's Disease Research Center and Rochester Epidemiology Project, a population-based evaluation of cognitive status of adults age 56-97 in Olmsted County, MN, ongoing since 1987, established the normative cognitive performance for the general population.

Neurological examination at the time of the assessment revealed no focal deficits in the 47 participants. MMSE scores were high with a mean of 28.6/30 and median of 29/30. Long-term survivors had lower scores on measures of long term memory and learning efficiency but higher than average scores on verbal intelligence quotient. Longer “call to shock” times were correlated with lower scores on measures of IQ, learning efficiency, delayed recall and MMSE.

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Experts who reviewed the paper for Neurology Today point out that the cohort in the study may have been exceptional, with optimal prospects for a good outcome, since patients who survive cardiac arrest to hospital discharge and beyond typically have the least degree of brain injury of all arrest victims. The majority of patients who were alive at the time of hospital dismissal had an OPC score of 1 (normal).

Even given that caveat, reviewers agree the study results are very promising. And they said the results establish a baseline for comparing outcomes for patients receiving other treatment strategies, such as hypothermia, and those suffering other forms of cardiac arrest.

Stephan A. Mayer, MD, professor of neurology and neurosurgery at Columbia University, noted that all of the 47 participants had experienced cardiac arrest that was witnessed and that the call-to-shock time was under six minutes. Nevertheless, he said the results speak to the dramatic improvements in neurocritical care of cardiac arrest patients. “The take-home message is that when everything works right, when the cardiac arrest is witnessed, the rhythm is shockable and patients receive excellent medical care with no complications, patients and families can expect a very good long-term outcome,” he told Neurology Today. “That's an important message for neurologists because we are the ones who often get called in to make a neurological prognosis.

“This really shows that the movement in neurocritical care within the last 15 years and the promotion of the chain of survival is rewriting the old rules,” he said. “Our classical notions about what is possible and what is impossible are being rewritten.”

J. Claude Hemphill, MD, chief of neurology at San Francisco General Hospital, agreed that the study cohort may not necessarily be representative of OHCA VF patients generally. “The overall survival rate was substantially higher than most other cohorts have found, and overall a lot more patients did well than in previous studies,” he said. “One wonders whether this speaks to either the overall health of the population in Olmsted County at baseline or the fact that in this particular location they do a much better job [of treating cardiac arrest] than other locations. That's an unknown.”

But Dr. Hemphill said the report is both encouraging and careful not to overstate its conclusions. “A very high proportion of those who survived had very good functional outcome,” he said. “This is a cause for optimism. Advanced neurological testing show some abnormalities, but they do not appear to profoundly impact the ability to lead reasonably functional lives.”

And Neurology Today editorial advisory board member Kevin Sheth, MD, a neurointensivist at the University of Maryland Medical Center and Shock Trauma Center, called the study “an achievement” that sets the stage for prospective studies of cognitive outcome for other cardiac arrest therapies. “This is the kind of data we will need going forward,” he said.

Dr. Mateen acknowledged that other parts of the country have much lower survival rates. But she said the lack of neurocognitive sequelae in long-term survivors of OHCA VF found in her study should lead to the continued widespread promotion of the chain of survival. And she credited the Cardiac Arrest Survival Network, a nationwide chain of support groups for cardiac arrest survivors, for helping to make the study possible.

“Patients and families have a real desire to know about the long-term outcome of a cardiac arrest,” she said. “They want to know whether survival [of a cardiac arrest] will mean that a patient will be able to have a normal life, and so far we haven't had the data to answer them.”

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Mateen FJ, Josephs KA, White RD, et al. Long-term cognitive outcomes following out-of-hospital cardiac arrest: A population-based study. Neurology 2011; E-pub 2011 Sept. 14.
Grossman M, Bleck TB. Where's the fire?: Long-term neurologic outcome following cardiac arrest. Neurology 2011; E-pub 2011 Sept. 14.
© 2011 American Academy of Neurology