INCREASE IN PLASMA BETA-ENDORPHINS PRECEDES VASODEPRESSOR SYNCOPE - ABSTRACTS

Background-Endogenous opioids have a tonic inhibitory effect on sympat hetic tone and have been implicated in the pathophysiology of vasodepr essor syncope. Plasma beta endorphin concentrations increase after vas odepressor syncope induced by exercise or by fasting. Aims-To take fre quent samples for plasma beta endorphin estimation during tilt testing , and to determine whether plasma beta endorphin increased before the start of syncope. Patients-24 patients undergoing tilt testing for inv estigation of unexplained syncope. Setting-Tertiary referral centre. M ethods-Blood samples were obtained during 70 degrees head up tilt test ing. Plasma beta endorphin concentrations were estimated by radioimmun oassay (mean(SD) pmol/l). Results-Patients with a positive test showed a rise in beta endorphin concentrations before syncope baseline 4.4(1 .5) v start of syncope 8.5(3.1), p < 0.002). In contrast, patients wit h a negative test showed no change in beta endorphin concentrations (b aseline 3.4(1.0) v end of test 4.5(2.3), NS). After syncope all patien ts showed a large secondary increase in beta endorphins (32.3(18.6)). Conclusion-An increase in plasma beta endorphins precedes vasodepresso r syncope. This finding supports a pathophysiological role for endogen eous opioids.