The QT interval is often prolonged in primary renal hypokalaemia-hypomagnesaemia, confirming that potassium and magnesium depletion tends to prolong the duration of the action potential of the cardiomyocyte. The results of continuous ambulatory electrocardiography, exercise testing and echocardiography are reassuring. Nonetheless, we assume that dangerous cardiac arrhythmias may occur in patients with very severe hypokalaemia, during medication with drugs that prolong the QT interval or in the context of short-term non-adherence to the recommended regimen of care.

Recent data demonstrate that patients affected with hypokalemic salt-losing tubulopathies are prone to acute cardiac arrhythmias and rhabdomyolysis. The tendency to these potentially fatal complications is especially high if chronic hypokalemia is severe, in patients with diarrhea, vomiting or a prolonged QT interval on standard electrocardiography, in patients on drug management with compounds prolonging the electrocardiographic QT interval (including antiarrhythmic agents, some antihistamines, macrolides, antifungals, psychotropics, ß 2 -adrenergic agonists or cisapride), following acute alcohol abuse and during exercise. Cardiac arrhythmias and rhabdomyolysis occur with sufficient frequency in hypokalemic salt-losing tubulopathies to merit wider awareness of their presence and the preparation of specific prevention and management recommendations.

In conclusion, severe chronic or acute hypokalaemia is hazardous in inborn salt-losing tubulopathies.

Potassium deficiency predisposes to cardiac arrhythmias culminating in syncope or sudden death. Because of the uncertainty related to the possible occurrence of such cardiac arrhythmias in the context of normotensive-hypokalemic tubulopathies, 19 European pediatric nephrologists with a large experience of normotensive-hypokalemic tubulopathies were asked to answer a questionnaire. The responses suggest that inherited normotensive-hypokalemic tubulopathies per se do not strongly predispose to dangerous cardiac arrhythmias. However, cardiac arrhythmias may be acutely precipitated by drugs that prolong the QT interval, by diarrhea, or vomiting, and perhaps even by physical activity. Finally, the likelihood of dangerous arrhythmias in normotensive-hypokalemic tubulopathy is currently unknown.