Effects of high salt intake and potassium supplement on QT interval dispersion in normotensive adults

Objectives: High salt intake not only raises blood pressure, but also has multi-effective independently of blood pressure, which directly induce target organ damage. Potassium as a sodium antagonist protects against cardiovascular systemic damage induced by excess salt intake. QT interval dispersion (QTd) has been suggested to reflect the heterogeneity of myocardial repolarization. There is evidence from experimental studies that heterogeneity in repolarization has been linked to the induction of malignant arrhythmia and sudden cardiac death. QTd has been widely used in hypertension, coronary heart disease, arrhythmia, evaluation of a drug and so on. The aim of this study was to investigate the effects of dietary sodium intake on QTd in normotensive healthy adults and protective effect of dietary potassium. Methods: Sixty-four normotensive subjects, aged 28 to 60, were enrolled and sequentially maintained on a protocol with 3 days baseline investigation, 7 days low salt diet (3 g/d, NaCl), 7 days high salt diet (18 g/d), and high salt diet with potassium supplementation (4.5 g/d, KCl) for another 7 days. A simultaneous 12-lead ECG was record by means of a 12-channel electrocardiograph at the last day of each period. QT interval, QTd and Tpeak-Tend interval (Tp-Te) were measured and calculated. Results: After salt loading, corrected QT interval (QTc), corrected QT interval dispersion (QTdc) and Tp–Te were prolonged (QTdc, 60.3±19.4 vs 55.6±19.4, P<0.05; Tp–Te, 83.0±10.1 vs 79.8±8.5, P<0.01). Surprisingly, all the changes can be reversed by potassium supplementation (QTd, 42.6±15.1 vs 47.4±19.0, P<0.05; QTdc, 52.2±18.0 vs 60.3±19.4, P<0.05; Tp–Te, 79.1±8.5 vs 83.0±10.1, P<0.01). Conclusion: Salt loading prolonged QT interval, QTd and Tp-Te in healthy adults, but dietary potassium supplementation could reverse these alterations. It suggests that potassium supplementation may improve heterogeneities of repatriation time and may prevent arrhythmias.