Abnormal Heart Rate Variability and Subtle Atrial Arrhythmia in Patients with Familial Amyloidotic Polyneuropathy

BACKGROUND: Cardiac autonomic dysfunction is a common complication of familial amyloidotic polyneuropathy (FAP), but cardiac arrhythmia and conduction disturbances are also common. We analyzed heart rate variability (HRV) in FAP patients using power spectrum analysis and Poincaré plot analysis. METHODS: HRV was analyzed in 24-hour ECG recordings (Holter) in 41 FAP patients. RESULTS: Power spectrum analysis showed reduced HRV in 21 FAP patients. A novel finding was that nine other patients with abnormal Poincaré plots had either very high power in the high-frequency region (0.15-0.50 Hz) or broadband HRV power spectra without any distinctive spectral peaks. Reanalysis of their ECGs showed a previously undetected intermittent atrial arrhythmia. CONCLUSIONS: Subtle arrhythmias may be difficult to detect during analyses of Holter recordings. Patients with intermittent atrial arrhythmia were identified by broadband HRV spectra and abnormal Poincaré plots. High high-frequency power in HRV and irregular heart rate patterns may indicate the presence of subtle atrial arrhythmia. Consequently, such patients should be excluded from studies of cardiac autonomic modulation.