Detection of serious bradyarrhythmias in Guillain-Barré syndrome: Sensitivity and specificity of the 24-hour heart rate power spectrum

This study was undertaken to determine the nature of brady-arrhythmic events and their relationship to motor disability, disease stages and tachycardia in patients with Guillain-Barré syndrome, and to investigate the potential of the 24-hour heart rate power spectrum (HRPS) for the detection of serious bradyarrhythmias in individual patients. Thirty-five consecutive patients with Guillain-Barré syndrome who were admitted to the authors' intensive care unit were studied. In all patients, the heart rate was continuously recorded during the early stages of the disease, averaged at 1-minute intervals, and stored for 1 to 87 days. The HRPS (n=556, 16±19 per patient; median, 9) was calculated by Fourier analysis of 24-hour recordings and logarithmically transformed. The slope was estimated by regression analysis of log (power) on log (frequency) between 10−4 and 4×10−3 Hz, showing an inverse power law behavior in all 556 HRPSs. Eleven patients (31%) had serious bradyarrhythmias. Most of these patients were not dependent on mechanical ventilation, with 3 of 11 patients (27%) still being able to walk more than 5 meters. Sustained tachycardia occurred less frequently in patients with than in those without bradyarrhythmias. The combination of the slope of the power law regression line and the log (power) at 10−4 Hz (log P4) of the 24-hour HRPS correctly identified 8 of 11 bradyarrhythmic patients (sensitivity 73%) and 16 of 22 patients with Guillain-Barré syndrome who did not have bradyarrhythmias (specificity 73%). All bradyarrhythmic patients could be detected in the subgroup of patients without sustained tachycardia. The 24-hour HRPS is a powerful predictor of serious autonomic complications in patients with Guillain-Barré syndrome and may help to identify patients at risk of potentially life-threatening arrhythmias.