[Diagnostic significance of absent nocturnal blood pressure decrease in 24-hour long-term blood pressure measurement]

Patients (pts) with essential hypertension normally exhibit a typical diurnal variation with a nocturnal blood-pressure (BP) decreased. A lack of this periodicity is often reported in pts with secondary hypertension. 24-h BP measurement was therefore performed in 308 pts with essential hypertension, and in 172 pts with secondary hypertension, in order to evaluate the diagnostic value of nocturnal BP decrease. Diagnoses of the secondary hypertensives were: renoparenchymatous hypertension (n = 29), diabetic nephropathy (n = 24), morbus Conn (n = 6), renal artery stenosis (n = 32), pheochromocytoma (n = 5), hemodialysis pts (n = 30), and kidney transplantation (n = 44). Pts with essential hypertension showed a mean systolic and diastolic BP decrease during the nighttime period of 22 +/- 7 mmHg and 17 +/- 5 mmHg, respectively. In contrast, the corresponding values in secondary hypertension were 5.7 +/- 9.2 mmHg (systolic decrease) and 5.2 +/- 5.9 (diastolic decrease). Pts with pheochromocytoma who had a nighttime increase in BP demonstrated the greatest difference from the essential hypertensives, followed by pts with either diabetic nephropathy or after kidney transplantation. A lack of nocturnal BP decline (less than 10% of the daytime values) was detected in 69.8% of pts with secondary hypertension, but only in 5.2% of pts with essential hypertension. In summary, these results suggest that the absence of a nighttime decline in BP during 24-h ambulatory monitoring is an indication of secondary hypertension and should lead to further investigations. Furthermore, a nightly hypertension is associated with a higher risk of complications.(ABSTRACT TRUNCATED AT 250 WORDS)