Electrocardiogram with prolonged QT interval in Gitelman disease.

Background: Potassium and magnesium deficiency prolong the QT interval on a standard electrocardiogram and predispose the patient to dangerous cardiac arrhythmias. No information is available on QT interval in patients diagnosed with Gitelman disease.

Methods: The QT interval was assessed on lead II in 27 patients with biochemically and genetically defined Gitelman disease, who had discontinued medical treatment for at least four weeks. They included 15 female and 12 male subjects, aged 6.7 to 40 years old, median 20 years old. The corrected QT interval was calculated from the measured QT interval and heart rate using the Bazett formula.

Results: The corrected QT interval was normal (between 391 and 433 msec) in 16 and prolonged in the remaining 11 patients (between 444 and 504 msec). Patients with prolonged and patients with normal QT interval did not significantly differ with respect to female to male ratio, plasma potassium, plasma total magnesium, and plasma ionized calcium. Plasma sodium and chloride values were slightly but significantly lower and bicarbonate levels higher in patients with a prolonged than in those with a normal QT interval.

Conclusions: The corrected QT interval is often pathologically prolonged in patients with Gitelman disease, suggesting that there is an increased risk for development of dangerous arrhythmias. Further investigations are required in patients with a prolonged QT interval to assess the true hazard of dangerous arrhythmias.