Circadian variation of late potentials in idiopathic ventricular fibrillation associated with J waves: Insights into alternative pathophysiology and risk stratification

Background

The presence of J waves on ECGs is related to idiopathic ventricular fibrillation (VF).

Objective

The purpose of this study was to investigate the pathophysiology of J waves by assessing risk markers that reflect electrophysiologic abnormalities.

Methods

The study enrolled 22 idiopathic VF patients (17 men and 5 women; mean age 36 ± 13 years). Patients were divided into two groups according to the presence or absence of J waves. The following risk stratifiers were assessed: late potentials (LPs; depolarization abnormality marker) for 24 hours using a newly developed signal-averaging system, and T-wave alternans and QT dispersion (repolarization abnormality markers). Frequency-domain heart rate variability (HRV), which reflects autonomic modulation, also was assessed. The results were compared to those of 30 control subjects with J waves and 30 with no J wave, matched for age and gender to the idiopathic VF patients.

Results

J waves were present in 7 (32%) idiopathic VF patients. The incidence of LP in the idiopathic VF J-wave group was higher than in the idiopathic VF non–J-wave group (86% vs 27%, P = .02). In contrast, repolarization abnormality markers did not differ between the two groups. In the idiopathic VF J-wave group, dynamic changes in LP parameters (fQRS, RMS₄₀, LAS₄₀) were observed and were pronounced at nighttime; this was not the case in the idiopathic VF non–J-wave group and the control J-wave group. High-frequency components (vagal tone index) on frequency-domain HRV analysis were associated with J waves in idiopathic VF patients (P < .05).

Conclusion

Idiopathic VF patients with J waves had a high incidence of LP showing circadian variation with night ascendancy. J waves may be more closely associated with depolarization abnormality and autonomic modulation than with repolarization abnormality.

Keywords: Circadian variation, Depolarization abnormality, Idiopathic ventricular fibrillation, J wave, Late potential

Abbreviations: fQRS, filtered QRS duration, HF, high frequency, HRV, heart rate variability, LAS₄₀, duration of low-amplitude signals (<40 μV) in terminal filtered QRS complex, LF, low frequency, LP, late potential, QTD, QT dispersion, RMS₄₀, root mean square voltage of terminal 40 ms of filtered QRS complex, TWA, T-wave alternans, VF, ventricular fibrillation