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Title: Dippers and non-dippers : potential causes and clinical significance of diurnal blood pressure variation
Author: Stewart, Michael John
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 1997
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Blunting of diurnal variability in some forms of secondary hypertension has been confirmed. Study of such patients provides an insight into potential mechanisms underlying the nocturnal dip. Catecholamine excess appears to have a profound effect, confirming the importance of the autonomic nervous system in its regulation. Attenuation of the dip in those with volume mediated hypertension and those with impaired renal function suggests that hypervolaemia resulting in posture related changes in BP may also impact upon this rhythm. Glucocorticoid excess has been shown to blunt diurnal variability, but a modest increase in glucocorticoid exposure in hypopituitary patients has no effect, suggesting that pathological but not physiological quantities of corticosteroid are required to modify the diurnal rhythm. Study of patients with accelerated phase hypertension has demonstrated loss of the diurnal rhythm which returns towards normal with successful treatment. However, such patients are commonly hospitalised and study of other groups requiring emergency hospital admission suggests that this process may in part explain this effect. Mean wake blood pressure has been shown to be the most important predictor of target organ damage, assessed by echocardiography and microalbuminuria, but some further independent predictive information is provided by knowledge of diurnal variability. The hypothesis that occult sleep apnoea or nocturnal hypoxia may account for loss of diurnal variability is tested. Patients with essential hypertension, sleep apnoea syndrome and chronic obstructive pulmonary disease were studied, with no direct link between nocturnal hypoxaemia and the night-time BP dip apparent. A potential active role for the heart in the control of the diurnal rhythm is examined in a study of patients with mild cardiac failure starting treatment with an ACE inhibitor. The nocturnal dip was preserved but blunted, and was reduced still further by treatment, due to a greater fall in day than night BP.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (M.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available