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Epilepsy Behav. 2010 Sep;19(1):78-81. doi: 10.1016/j.yebeh.2010.06.011. Epub 2010 Jul 27.

RMSSD, a measure of vagus-mediated heart rate variability, is associated with risk factors for SUDEP: the SUDEP-7 Inventory.

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Department of Neurology, David Geffen-UCLA School of Medicine, Los Angeles, CA 90095, USA.



The goal of this study was to determine if specific measures of heart rate variability (HRV) are associated with the total score on a new seven-item inventory for sudden unexplained death in epilepsy (SUDEP).


Nineteen subjects with intractable partial seizures, at least three per month, were enrolled in a randomized clinical trial of omega-3 fatty acids in epilepsy. At study entry, subjects underwent a 1-hour ECG recording for the determination of HRV. To estimate the risk of SUDEP, we assembled a seven-item inventory (the SUDEP-7 Inventory) from risk factors prospectively validated by T.S. Walczak, I.E. Leppik, M. D'Amelio M, et al. (Neurology 2001;56:519-25). The SUDEP-7 score was then correlated with measures of HRV using the Pearson correlation and other parametric and nonparametric methods.


Subjects had highly drug-resistant seizures, with a mean seizure frequency of 22.8 seizures per month. Scores on the SUDEP-7 inventory ranged from 1 to 7 of a maximum possible score of 12. RMSSD, a measure of high-frequency HRV, was inversely correlated with the SUDEP-7 score, r=-0.64, P=0.004. Subjects with higher SUDEP-7 scores had reduced levels of HRV (RMSSD). Other time-dependent measures of HRV (SDNN, SDANN) were not significantly correlated with SUDEP risk scores.


RMSSD, a measure of HRV, which reflects the integrity of vagus nerve-mediated autonomic control of the heart, is highly associated with the total score on a new seven-item SUDEP risk inventory. Lower RMSSD values were associated with higher risk scores on the new SUDEP risk inventory. This provides new evidence that HRV (specifically RMSSD) is a marker of SUDEP risk.

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