P40 | Indirect estimation of plasma volume in chronic constitutional hypotension

S. Cencetti¹, M. Vinci¹, G. Visi², C. Cassetti³, L. Parigi¹ | ¹Cardiologia, Ospedale P. Palagi, Firenze, ²Day Service Multidisciplinare, Ospedale P. Palagi, Firenze, ³Scuola di Scienze della Salute Umana, Università degli Studi di Firenze, Italy

Aims: Chronic Constitutional Hypotension (CCH) is defined for stable value of arterial pressure, less than 110/60 mmHg in men and 100/60 mmHg in women. This idiopathic condition was demonstrated as associated to asthenia and syncope. We searched for a link between symptoms and plasma osmolality, intended as an indirect index of plasma volume depletion.
Methods: We studied 114 females who matched the criteria for CCH: 71 subjects symptomatic for syncope, 36 for presyncope only and 8 asymptomatic. Age, body mass index, blood pressure values, presence of orthostatic blood pressure decrease and plasma osmolality were used for statistical analysis. Comparisons were made between the syncopal and non syncopal groups. Analysis of variance (ANOVA) was performed for continuous data, and χ2 for categorical data; significance was set for p<0.05.
Results: No significant differences were found between the two groups for age, body mass index and basal pressure values. Orthostatic decrease of systolic blood pressure ≥10 mmHg was present in 77.5% of the syncopal subjects and in 47% of the non syncopal ones (p<0.01). Plasma osmolality was higher in syncopal subjects (294 vs. 291 mOsm/kg, p 0.017). Orthostatic decrease of systolic blood pressure was observed in 74.4% of the subjects with plasma osmolality higher than the reference values (>295 mOsm/kg).
Conclusions: In CCH elevated plasma osmolality is inked to orthostatic blood pressure decrease and syncope as clinical features. This may indicate basal hypovolemia as the underlying cause thus possibly lead to therapeutic choices