Atrial natriuretic factor: a possible link between left atrium, plasma volume, adrenergic control and renin-aldosterone in the mitral valve prolapse syndrome.

The immunoreactive atrial natriuretic factor (ANF) was measured by radioimmunoassay after extraction with SEP-PAK cartridges in 16 hyperadrenergic patients with the mitral valve prolapse (MVP) syndrome. Plasma renin activity and plasma aldosterone were concomitantly measured by radio-immunoassay. Plasma and blood volumes were obtained indirectly after measurement of red cell volume. Norepinephrine and epinephrine were measured by a radio-enzymatic microtechnique. Seven out of 16 patients (44%) had high values of immunoreactive ANF. Blood volume was uniformly decreased in MVP patients, but this was more marked in patients with high ANF. There was a significant correlation between ANF and the reduction in blood volume. Plasma norepinephrine was not significantly different in patients with high ANF and low or normal ANF. Thus, some patients with the MVP syndrome may have both an increased adrenergic state and abnormal values of ANF. The interplay between these two neuro-endocrine disorders may account for some of the symptoms of these patients. The data confirm that this syndrome may be associated with a complex 'neuro-endocrine cardiovascular process'.