Haemodynamic diversity and plasma renin activity in labile arterial hypertension.

Haemodynamic studies were made on 31 patients with labile hypertension at rest and during exercise. Plasma renin activity (PRA) was measured in 8 of them. Five haemodynamic types could be recognised and they could be arranged into two groups. The first was characterised by an increase of calculated peripheral resistance, sometimes permanent, sometimes revealed by effort, sometimes in relation to an increased cardiac output; this would appear to predict the development of permanent hypertension. The second group was characterised by normal systemic resistances, adapted to the cardiac output which was either normal or increased; the significance of labile hypertension in these cases was uncertain; from the haemodynamic studies one was unable to distinguish a transient emotive hypertension from potential permanent hypertension. The PRA was raised in the supine position and greatly increased by an orthostatic posture in the 8 patients tested, suggesting therefore an underlying neuro-adrenergic mechanism. In some patients with labile hypertension the haemodynamic tests were normal at rest and during effort. Others had different responses, which may be the result of varieties of hyper-sympathetic activity, either pure or predominantly beta-adrenergic (increased cardiac output, peripheral resistance adapted to the output) or combined beta and alpha (increased cardiac output with raised peripheral resistance) or mainly alpha-adrenergic (normal cardiac output, increased peripheral resistance).