In the current issue of the , Baek et al. report that the presence of early repolarization (ER) pattern is independently associated with a slow heart rate, male sex, and increased vagal activity (based on Holter parameters) in a Korean population without obvious structural heart disease. They report a trend toward a higher high frequency (HF) components and a lower low frequency/HF ratio in subject with J wave compared to those without. As already published , in patients with idiopathic ventricular fibrillation (VF), HF components increased during nighttime versus daytime and is higher in patients with ER pattern compared to patients without this pattern both during daytime and nighttime. One of the strength of this manuscript is the number of patients studied (n = 684) even if the study was retrospective. Other groups already pointed out the relationship between J wave amplitude and bradycardia. Mizumaki et al. compared patients with J wave with (n = 8) or without idiopathic VF (n = 22). They demonstrated that J wave amplitude was independently modulated by both heart rate and vagal activity in normal subjects and in patients with idiopathic VF and ER. By using ambulatory recordings, they demonstrated in a very simple manner a significant increase in J wave amplitude when the heart rate slowed or during increased levels of vagal activity, both phenomena culminated at night. Interestingly in patients with idiopathic VF as compared to control subjects, J wave elevation was more strongly augmented during bradycardia and was associated with an increase in vagal activity. A direct relationship existed between HF components of heart rate variability and the amplitude of J waves in patients with ER and idiopathic VF, but also in their control group although much weaker. Baek et al. find a similar tendency in normal subject with J wave. They also compare functional capacity, peak heart rate, and ST changes during stress test in a small subgroup of patients with versus without ER pattern. No significant difference between patients with and without ER pattern was identified. Unfortunately, there is no description of the ER pattern or ST orientation (horizontal/descending or rapidly ascending/upsloping) during stress test. Classically, ER pattern disappears at increased heart rate.
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