AIMS: A retrospective, case-control study to investigate the J wave, a J-point 
elevation on resting 12-lead electrocardiograms, as a risk factor for sudden 
cardiac arrest (SCA) in patients diagnosed with hypertrophic cardiomyopathy 
(HCM).
METHODS: Patients with HCM and age- and sex-matched healthy control subjects 
were recruited, and 12-lead electrocardiograms were performed. The prevalence 
and related characteristics of J waves were assessed. Patients were followed-up 
for a mean of 47.9 months.
RESULTS: Patients with HCM (n = 345) had significantly higher prevalence of J 
waves than healthy controls (n = 690; 11.6% and 7.1%, respectively). During 
follow-up, 14 patients with HCM experienced SCA (SCA subgroup). The prevalence 
of J waves was significantly higher in the SCA subgroup than in the non-SCA 
subgroup (42.9% and 10.3%, respectively). There were no significant differences 
between the SCA and non-SCA subgroups in J wave morphology.
CONCLUSION: The J wave may be a risk factor for SCA in patients with HCM.