Salt Loading on QT Dispersion and the Protective Role of Potassium Supplement in Normotensive Adults

Abstract

QT interval dispersion (QTd) has been suggested to reflect the heterogeneity of myocardial repolarization and 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 and T peak -T end interval (Tp-Te) in normotensive healthy adults and the protective effect of dietary potassium. Sixty-four normotensive subjects aged 20~60 were selected and involved in a 3-week test in chronic salt loading and potassium supplementation, including baseline survey (baseline phase) for 3 d, low-salt diet (3g/day, NaCl, low-salt phase), high-salt diet (18g/day, salt loading phase) and high-salt with potassium supplementation diet (4.5g/day, KCl, salt and potassium supplement phase) each for 7 d. Blood pressure was measured and ECG was recorded at the last day of each phase, QT interval, QTd, corrected QTd (QTcd) and Tp-Te were measured and calculated. QTd, QTcd and Tp-Te at low-salt phase were less than those at baseline phase (QTd, 45.6±7.6ms vs. 52.1±9.4ms; QTcd, 53.4±8.4ms vs. 62.9±10.1ms; Tp-Te, 75.2±8.2ms vs. 85.0±9.6ms, P±0.05); QTcd and Tp-Te after salt loading were greater than those at low-salt phase (QTcd, 62.3±7.9ms vs. 53.4±8.4ms; Tp-Te, 84.7±10.0ms vs. 75.2±8.2ms, P<0.05); compared with those at salt loading phase, QTd, QTcd and Tp-Te were all reduced by large doses of oral potassium supplementation(QTd, 42.6±8.3ms vs. 53.4±9.1ms; QTcd, 52.2±6.2ms vs. 62.3±7.9ms; Tp-Te, 75.1± 8.5ms vs. 84.7±10.0ms, P±0.05). Salt loading increases blood pressure and prolongs QTd, QTcd and Tp-Te, while potassium supplementation reduces the influences of high salt on QTd, QTcd and Tp-Te, suggesting that high potassium intake may decrease the heterogeneity of cardiac repolarization and prevent arrhythmia by shortening repolarization time.