Detecting sodium-sensitivity in hypertensive patients: Information from 24-hour ambulatory blood pressure monitoring

Sodium sensitivity is an important cardiovascular risk factor for which a diagnosis requires a time-consuming protocol, the implementation of which is often challenging for patients and physicians. Our aim was to assess the reliability of an easier approach based on data from 24-hour ambulatory blood pressure monitoring performed in hypertensive subjects during daily-life conditions and habitual diet. We enrolled 46 mild to moderate hypertensive subjects who underwent 24-hour ambulatory blood pressure monitoring during usual sodium intake. Patients were divided into 3 classes of sodium sensitivity risk on the basis of ambulatory blood pressure monitoring data: low risk if dippers and a 24-hour heart rate ≤70 bpm; high risk if nondippers and a 24-hour heart rate of >70 bpm; intermediate risk with the remaining combinations (dippers with heart rate >70 bpm or nondippers with heart rate ≤70 bpm). Then patients underwent a traditional sodium sensitivity test for the dichotomous classification as sodium sensitive or sodium resistant and for evaluating the sodium sensitivity index. Prevalence of sodium-sensitive patients and mean value of sodium sensitivity index were calculated in the 3 risk classes. The sodium sensitivity index markedly and significantly increased from the low-risk to the high-risk class, being equal to 19.9±14.4, 37.8±8.3, and 68.3±17.0 mm Hg/(mol/day) in the low-risk, intermediate-risk, and high-risk classes, respectively (M±SEM). Also, the prevalence of sodium-sensitive patients increased significantly from the low-risk class (25%) to the intermediate-risk (40%) and high-risk (70%) classes. Thus, performance of 24-hour ambulatory blood pressure monitoring in daily-life conditions and habitual diet may give useful information on the sodium sensitivity condition of hypertensive subjects in an easier manner than with the traditional sodium sensitivity test approach.