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Sudden Cardiac Death - It's the brain, stupid!

Posted Dec 18 2008 1:31pm

Ever since 1849, when Carl Ludwig first documented ventricular fibrillation (VF), doctors have known that this potentially lethal arrhythmia can occurs in heart. VF almost always leads to a cardiac arrest and death (SCD) within minutes if left untreated. It was always - naturally - assumed that it originated in the heart itself. As such, researchers kept concentrating on evaluating people's hearts to try to help decide who was at greatest risk of VF/SCD. More recent research, however, has strongly suggested that, while VF manifests itself in the heart, it originates in the brain. In animal experiments, stimulating critical higher centers in the brains of animals with normal hearts can cause VF while, conversely, severing all the nerve connections between the brain and heart completely prevents its occurence. Thus, by only looking at the heart and ignoring the brain, doctors were all along missing a critical piece of the puzzle. Even if they wanted to look at the brain-heart interaction, they did not have the proper tools to do so. Now, however, a new mathematical method allows for the analysis of the ECG signal to assess the brain-heart interaction in people and seem to highly accurately discriminate ("risk stratify") between those patients whose brains will let their hearts go into VF and those whose brains will not.

All this lends itself to some pretty exctiting stuff, including the possibility of preventing many of the ~310,000 sudden cardiac deaths that occur annually in the US alone. Those individuals identified as at high risk for VF could be directed towards preventative treatment before disaster struck.

Up until now, risk stratification techniques have, for the most part, performed dismally. About 75% of people who receive an implantable defibrillator (ICD) for VF/SCD never need the device (false positive), yet around 80% of people who did have VF/SCD weren't eligible for an ICD by the current criteria (false negative). In contrast, one new method  based upon the brain-heart interaction seems to be extremely accurate.

This new way of looking at VF/SCD represents a sea change in the way doctors view this problem, and requires a re-education, of sorts. Hopefully, as the data mounts in favor of these new methods, physicians will be better equipped to help prevent SCD. To paraphrase a political slogan from not too long ago - it's not the [just] heart,"it's the brain, stupid!"

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