Nocturnal hypertension: poor correlation with office blood pressure but strong prognostic factor for target organ damage.

INTRODUCTION: We investigated the correlation between systolic and diastolic nocturnal blood pressure (BP) values and office BP values, as well as parameters of 24-hour ambulatory BP monitoring, in patients with hypertension. In addition, we compared nocturnal hypertensives with nocturnal normotensives regarding their demographic, clinical, and laboratory characteristics, as well as other data from 24-hour BP monitoring.
METHODS: The study included 182 consecutive patients who had newly diagnosed, never treated, uncomplicated arterial hypertension. Blood samples were obtained from all patients for the determination of glycaemic and lipidaemic profiles. All underwent a complete echocardiographic examination, including tissue Doppler imaging, measurement of carotid intima-media thickness, measurement of carotid-femoral pulse wave velocity, and determination of the augmentation index of reflected waves (Aix@75), as well as 24-hour ambulatory BP monitoring. The population was divided into nocturnal normotensives (NN, n=77) and nocturnal hypertensives (NH, n=105, nocturnal BP >120/70 mmHg).
RESULTS: Although the NH did not differ from the NN as regards the classical cardiovascular risk factors, they showed an excessive inotropic response to exercise (61.9% vs. 22.7%, p=0.028), higher levels of serum uric acid (5.5 ± 1.56 mg/dl vs. 4.7 ± 1.36 mg/dl, p=0.003), as well as greater arterial stiffness, as expressed by a higher carotid-femoral pulse wave velocity (8.6 ± 1.6 m/s vs. 7.9 ± 1.4 m/s, p=0.009), and a greater carotid intima-media thickness (0.74 ± 0.17 mm vs. 0.68 ± 0.15 mm, p=0.007). In addition, although the two groups did not differ significantly as regards office BP values and did not show strong correlations between nocturnal and office BP, both nocturnal diastolic and, especially, systolic BP showed strong correlations with levels of serum uric acid and with subclinical lesions in the heart, central aorta, peripheral vessels, and renal vasculature.
CONCLUSIONS: Nocturnal BP is poorly correlated with office BP values. However, the presence of nocturnal hypertension is associated with morphological and functional disturbances of the cardiovascular net. 24-hour ambulatory BP monitoring is an essential tool for revealing this subgroup of hypertensive patients who are at increased cardiovascular risk.