Low blood pressure phenotype underpins the tendency to reflex syncope

BACKGROUNDWe hypothesized that cardiovascular physiology differs in reflex syncope patients compared with general population, predisposing such subjects to vasovagal reflex.METHODSIn this multicohort cross-sectional study, we compared resting systolic blood pressure (SBP), diastolic blood pressure (DBP), pulse pressure (PP) and heart rate (HR), collected from 6 community-based cohort studies (64,968 observations) with those from 6 databases of reflex syncope patients (6516 observations), subdivided by age decades and sex.RESULTSOverall, in males with reflex syncope, SBP (−3.4 mmHg) and PP (−9.2 mmHg) were lower and DBP (+2.8 mmHg) and HR (+5.1 bpm) were higher than in the general population; the difference in SBP was higher at ages >60 years. In females, PP (−6.0 mmHg) was lower and DBP (+4.7 mmHg) and HR (+4.5 bpm) were higher than in the general population; differences in SBP were less pronounced, becoming evident only above 60 years. Compared with males, SBP in females exhibited slower increase until age 40, and then demonstrated steeper increase that continued throughout life.CONCLUSIONThe patients prone to reflex syncope demonstrate a different resting cardiovascular hemodynamic profile characterized by reduced venous return and stroke volume, evidenced by lower SBP and PP, and compensatory increase in HR and vascular resistance, the latter expressed by elevated DBP. The data presented here contribute to our understanding why some subjects with similar demographic characteristics develop reflex syncope and others not.