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, RMS(40), LAS(40)) 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.