Heart Rate Variability in Huntington Disease: A Long-Term Longitudinal Study.

Introduction: The aim of the study was to follow tonic and phasic autonomic nervous activity in Huntington disease (HD) mutation carriers and patients.

Methods: Evaluation of motor functions and total functional capacity was performed in 30 HD mutation carriers or patients at the beginning and in 22 subjects after 8-10 years. Continuous arterial blood pressure, heart rate (HR), and ECG at rest were measured, and HR variability analysis was performed in four different ways. A group of matched controls was also evaluated.

Results: Eighteen subjects were assorted in 3 groups: 6 HD mutation carriers without motor symptoms (PHD) who remained so (PHD-PHD); 6 early symptomatic patients (EHD) who remained so (EHD-EHD); and 6 early symptomatic patients who deteriorated to a late symptomatic (LHD) (EHD-LHD). At the beginning, sympathetic tonic activity in PHD was elevated, according to mean arterial pressure (99 ± 10.6 mm Hg) higher than in controls (85 ± 8.7 mm Hg) and EHD (82 ± 9.9 mm Hg) (Dunnett's test, p < 0.05) and higher HR (78 ± 16 beats/min) than after 8-10 years (64 ± 11.3 beats/min) (paired t test, p < 0.05). There was also a decreased phasic sympathetic activity in EHD patients compared controls at the beginning (219 ± 106 vs. 664 ± 466 s2/Hz) and after 8-10 years (182 ± 136 vs. 1,012 ± 1,369 s2/Hz) (Dunnett's test, p < 0.05). In patients who deteriorated from EHD to LHD, there was a drop in phasic parasympathetic activity from 887 ± 433 to 230 ± 235 s2/Hz (paired t test, p < 0.05).

Conclusions: Our long-term observational study provides important information on the timeline of ANS activity in HD progress. There was a temporary increase in cardiac and vascular sympathetic activity in PHD subjects. The normalization of HR in PHD subjects might indicate the approach of an outbreak of clinical disease phase.