Can secondary hypertension be identified by twenty-four-hour ambulatory pressure monitoring?

Circadian blood pressure rhythms were examined in subjects exhibiting various forms of secondary and essential hypertension and in normotensive subjects with and without renal disease. Indirect ambulatory blood pressure recordings were performed in 284 subjects for 24 h. In contrast to patients with essential hypertension and to normotensive healthy subjects, the circadian fluctuations of blood pressure were reduced in secondary hypertensives and in normotensive renal patients. In renal hypertensives, these alterations in the diurnal blood pressure variations were dependent on the degree of renal failure. Calculations based on comparisons of the mean sleeping and mean daytime blood pressures identified 89.8% of the essential hypertensives and 72.5% of the patients with secondary hypertension. A large proportion of the patients with secondary hypertension had very high blood pressure levels during sleep, in many cases even exceeding the daytime levels. Thus, 24-h ambulatory blood pressure curves from patients with secondary and essential hypertension can be distinguished from each other. In secondary hypertension, blood pressure monitoring during both day and night is particularly useful for evaluating frequently severe nocturnal hypertension, which may require particular treatment.