[Importance of 24-hour blood pressure monitoring in secondary hypertension].

A typical diurnal variation in blood pressure is observed in patients with essential hypertension. Attenuation or lack of circadian periodicity might be expected in patients with secondary hypertension. Therefore, non invasive ambulatory blood-pressure monitoring was performed in 172 patients with secondary hypertension and in 201 patients with essential hypertension. The following patients with secondary hypertension were investigated: renoparenchymatous nephropathy (n = 29), diabetic nephropathy (n = 24), morbus Conn (n = 6), renal artery stenosis (n = 32), pheochromocytoma (n = 5), hemodialysis patients (n = 30), and patients after kidney transplantation (n = 44). In addition, 36 pregnant women (17 normotensives, 19 hypertensives) were studied. 98.5% of patients with essential hypertension showed a nightly decline in blood pressure of at least 15 mmHg (systolic + diastolic), whereas 70% of patients with secondary hypertension showed either an attenuated circadian rhythm or no circadian rhythm. Patients with pheochromocytoma who had a nighttime increase in blood pressure demonstrated the greatest difference in the essential hypertension collective, followed by patients with diabetic nephropathy and patients after kidney transplantation. After successful treatment of the condition leading to hypertension, circadian periodicity returned in some patients. In summary, these results suggest that the absence of a nighttime decline in blood pressure during 24-h-ambulatory monitoring is an indication of secondary hypertension, which should be further investigated. As a practical consequence, antihypertensive drugs should also be applied in an evening dose in secondary hypertensives. Noninvasive ambulatory blood-pressure monitoring is recommended for treatment control, especially in patients who need an efficient blood-pressure control.