Gender related differences in active renin, aldosterone and big endothelin concentration during head-up tilt testing in patients with isolated vasovagal syncope

Abstract

Neuroendocrine dysregulation seems to play the main role in liberation of abnormal vasovagal reflex, and the pathomechanism can be gender-related. The aim of the study was to assess changes in concentration of active renin (R), aldosterone (A) and big endothelin (BE) at rest and tilting in patients with vasovagal syncope in reference to gender and result of the head-up tilt test (HUTT).Study involved 133 patients with syncope. In all HUTT were performed. Concentrations of the analyzed hormones were measured at the last minute of the rest, at the 10th minute of tilting and at the end of the test. An aldosterone/renin ratio (A/R) was calculated for each of the phases.HUTT(+) was observed in 87subjects (65%). During tilting a gradual increase of R and A was observed. The highest A/R was present in women HUTT(-) (p=0.040), contrary to non-fainting men in which decrease of A/R was accompanied with the highest absolute values at the end of the test (>18.6 pg/ml and A/R ratio at the end of the test <2.53 revealed to be independent predictors of syncope during tilt. The increase of R concentration during tilting <1.26 fold and the lack of increase of A predicted syncope during passive phase. In men, A concentration at the end of the test <44.0 pg/ml and the increase of A during tilting less than 2.10 fold, independently predicted positive result. None of analyzed parameters was pointed as an independent factor of syncope during passive phase. In women, R concentration at 10th minute of tilting >18.6 pg/ml and A/R ratio at the end of the test <2.53 revealed to be independent predictors of syncope during tilt. The increase of R concentration during tilting <1.26 fold and the lack of increase of A predicted syncope during passive phase. In men, A concentration at the end of the test <44.0 pg/ml and the increase of A during tilting less than 2.10 fold, independently predicted positive result. None of analyzed parameters was pointed as an independent factor of syncope during passive phase.The activity of the vasoactive hormones is different in women and men and can determine the result of the test and the tolerance to passive tilting.