Background Sodium (Na+) stored in skin and muscle tissue is associated with essential hypertension. Sodium magnetic resonance imaging is a validated method of quantifying tissue stores of Na+. In this study, we evaluated tissue Na+ in patients with elevated blood pressure or stage I hypertension in response to diuretic therapy or low Na+ diet. Methods and Results In a double-blinded, placebo-controlled trial, patients with systolic blood pressure 120 to 139 mm Hg were randomized to low sodium diet (<2 g of sodium), chlorthalidone, spironolactone, or placebo for 8 weeks. Muscle and skin Na+ using sodium magnetic resonance imaging and pulse wave velocity were assessed at the beginning and end of the study. Ninety-eight patients were enrolled to undergo baseline measurements and 54 completed randomization. Median baseline muscle and skin Na+ in 98 patients were 16.4 mmol/L (14.9, 18.9) and 13.1 mmol/L (11.1, 16.1), respectively. After 8 weeks, muscle Na+ increased in the diet and chlorthalidone arms compared with placebo. Skin sodium was decreased only in the diet arm compared with placebo. These associations remained significant after adjustment for age, sex, body mass index, systolic blood pressure, and urinary sodium. No changes were observed in pulse wave velocity among the different groups when compared with placebo. Conclusions Diuretic therapy for 8 weeks did not decrease muscle or skin sodium or improve pulse wave velocity in patients with elevated blood pressure or stage I hypertension. Registration URL: https://www.clinicaltrials.gov; Unique identifier: NCT02236520.
Keywords: diuretics; hypertension; prehypertension; salt intake; sodium; sodium MRI; tissue sodium.