Circadian heart rate and blood pressure variability in autonomic failure

Autonomic failure (AF) induces disabling orthostatic symptoms. Short-term heart rate (HR) and blood pressure (BP) orthostatic patterns are well characterized in these patients but data on long-term blood pressure and heart rate monitoring is lacking. The aim of this study was to assess circadian HR and BP variation in AF patients. We studied 8 patients with severe AF (7 with TTRmet30+ familial amyloidotic polyneuropathy and 1 with pure autonomic fairure)--Group A, and 2 control groups (8 asymptomatic TTRmet30+ patients--Group B, and 16 normal aged-matched controls--Group C). All groups underwent 24h HR and BP monitoring. Twenty-four-hour systolic (SBP) and diastolic BP (DBP) were similar in all groups (114.5+/-10.6 and 73.2+/-6.7; 123.0+/-6.2 and 79.0+/-9.5; 118.6+/-10.1 and 71.4+/-9.4 mmHg for groups A, B and C respectively). BP dipping was attenuated or even inverted (p < 0.01) in AF patients (SBP and DBP differences between day and night: -1.6+/-11.6 and 3.3+/-6.3; 10.0+/-1.0 and 11.7+/-1.5; 15.6+/-7.9 and 16.2+/-5.8 mmHg for groups A, B and C respectively; p < 0.01). Although mean 24h HR was similar between patients and controls (80.9+/-14.0, 87.0+/-4.6 and 80.7+/-5.2 bpm for groups A, B and C respectively), there were striking differences in heart rate variability between groups (max-min 24h HR difference: 46+/-16, 89+/-11 and 91+/-9 bpm; pNN50: 0+/-0, 6+/-2 and 12+/-6%; SDRR 68+/-24, 128+/-10 and 148+/-32 ms for groups A, BB and C; p < 0.01). There were significant differences between normal controls and asymptomatic TTRmet30+ controls in mean HR, diastolic blood pressure dipping and pNN50; p < 0.05. Autonomic failure can be suspected by simple 24h blood pressure evaluation and heart rate monitoring. Asymptomatic TTRmet30+ patients may already show some degree of autonomic impairment, particularly early vagal dysfunction.