International guidelines recommend restriction of activities for many children and adolescents with inherited arrhythmia syndromes to moderate activity (<7 metabolic equivalents [METs]). We hypothesized that moderate levels of intensity would be exceeded during free-living daily activity in these individuals when assessed objectively by combined heart rate and accelerometry monitor (Actiheart).Methods and Results—
Participants wore the Actiheart for ≤7 days on 2 occasions after a maximal exercise test that was used to calibrate the monitor individually against intensity levels. Of 16 participants, 13 (81%) had long QT syndrome, 9 (56%) were female, and median age was 12 years. Monitors were worn for a median (range) of 13 (6–14) days, and a mean (SD) of 11.3 (1.7) hours per day. Vigorous (7 MET) and very vigorous (10 MET) thresholds were exceeded by 15 and 13 participants, respectively. The median (interquartile range), individual, total weekly time spent >7 MET threshold was 113 (65–330) minutes, whereas such time spent >10 MET threshold was 53 (9–115) minutes. Total time >7 MET threshold was 2.3% of monitor wear time. There were no differences in time above threshold between male and female participants (P=0.357) or among those with different levels of activity restriction (P=0.769).Conclusions—
Current recommended activity guidelines are frequently exceeded during routine free-living activities in young participants with inherited arrhythmia syndromes. Whether this indicates increased risk for these individuals or excessively restrictive guidelines remains to be determined.