The hypotensive mechanism of percutaneous transluminal dilatation (PTD) in renovascular hypertension due to bilateral renal artery was investigated in two patients. Blood pressure was monitored continously before, during and after PTD by use of a new automated blood pressure monitoring device based on finger volume-oscillometry. Plasma renin activity was measured repeatedly before, during and after PTD. A hypotensive effect appeared immediately after PTD and blood pressure remained low in the following observation period without any hypotensive medication. In these cases, the hypotension was accompanied by a transient decrease in heart rate immediately after PTD. The hypotensive response to PTD was not parallel to the basal plasma renin activity, suggesting that the renin-angiotensin system is not necessarily involved in the maintenance of the hypertension before PTD. The autonomic nervous system seemed to play a certain role. Since the hypotension was accompanied by a transient decrease in heart rate immediately after PTD, the hypotension may be induced either by a decrease in sympathetic tone or by an increase in vagal tone at least just after PTD. It is hypothesized that these changes in autonomic nervous activity are mediated centrally through the renal afferent mechanism in response to rapid changes in renal hemodynamics induced by PTD.
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