Department of Cardiology, Asahikawa Medical University
Background: Intravenous administration of magnesium (Mg2+) is effective for polymorphic ventricular tachycardia via homogenization of transmural ventricular repolarization. Mg2+ likely plays some role in the heterogeneity of repolarization in J wave syndromes. Objective: To investigate the relationship between the repolarization parameters and serum Mg2+, potassium (K+), and calcium (Ca2+) levels in J wave syndromes. Methods: Thirteen J-wave syndrome patients (Brugada and early repolarization [ER] syndromes), with documented episodes of ventricular fibrillation (VF), and 13 ER pattern (ERP) or Brugada type ECG patients were enrolled (25 males, mean age 48 ± 15 years). The 12-lead ECG-derived parameters including the QT, QT dispersion (QTd), Tpeak-Tend (Tp-e) interval, Tp-e dispersion (Tp-ed), Tp-e/QT ratio, and activation recovery interval (ARI) dispersion were calculated; the correlations between these parameters and electrolytes including Mg2+, K+, and Ca2+ were analyzed. Results: Although there was no association between serum K+ or Ca2+ and QTd, there was a strong negative correlation between serum Mg2+ and QTd in J wave syndrome patients with a history of VF (r = -0.715, p = 0.006). Also, there was a tendency for a negative correlation between Mg2+ and Tp-ed or ARI dispersion in J wave syndrome patients with a history of VF (r = -0.513, p = 0.072 and r = -0.53, p = 0.063, respectively). On the other hand, in 13 patients with a Brugada type ECG or ERP, no correlation was observed between serum Mg2+ and the QTd, Tp-ed or ARI dispersion. Conclusion: Serum Mg2+ may play an important role in the cardiac repolarization process in J wave syndromes.