Heart rate changes associated with autonomic dysreflexia in daily life of individuals with chronic spinal cord injury

Study design Secondary data analysis. Objective To characterize heart rate (HR) changes during autonomic dysreflexia (AD) in daily life for individuals with chronic spinal cord injury (SCI). Setting University-based laboratory/community-based outpatient. Methods Cardiovascular data, previously collected during a 24-h ambulatory surveillance period in individuals with chronic SCI, were assessed. Any systolic blood pressure (SBP) increase >= 20 mmHg from baseline was identified and categorized into confirmed AD (i.e., diarized trigger), unknown (i.e., no diary entry), or unlikely AD (i.e., potential exertion driven SBP increase) groups. SBP-associated HR changes were categorized as unchanged, increased or decreased compared to baseline. Results Forty-five individuals [8 females, median age and time since injury of 43 years (lower and upper quartiles 36-50) and 17 years (6-23), respectively], were included for analysis. Overall, 797 episodes of SBP increase above AD threshold were identified and classified as confirmed (n = 250, 31.4%), unknown (n = 472, 59.2%) or unlikely (n = 75, 9.4%). The median number of episodes per individual within the 24-h period was 13 (8-28). HR-decrease/increase ratio was 3:1 for confirmed and unknown, and 1.5:1 for unlikely episodes. HR changes resulting in brady-/tachycardia were 34.4%/2.8% for confirmed, 39.6%/3.4% unknown, and 26.7%/9.3% for unlikely episodes, respectively. Conclusions Our findings suggest that the majority of confirmed AD episodes are associated with a HR decrease. Using wearable-sensors-derived measures of physical activity in future studies could provide a more detailed characterization of HR changes during AD and improve AD identification.