The percentage of cardiac baroreflex sequences is independent from the sign of arterial pressure variations in healthy subjects

The sequence (SEQ) method can be exploited to differentiate the patterns of cardiac baroreflex origin according to the sign of systolic arterial pressure (SAP) variations. Indeed, this method distinguishes between patterns featuring heart period (HP) lengthening in response to SAP increase (SEQ++) from those featuring HP shortening in response to SAP decrease (SEQ–). The aim of the study was to compare the proportion between SEQ++ and SEQ– in healthy subjects at rest in supine condition (REST) and during active standing (STAND). One-hundred healthy subjects, divided into five groups based on age (21-30,31-40,41-50,51-60,61-70 yrs), were studied at REST and during STAND. The percentages of SEQ++ (%SEQ++) and SEQ– (%SEQ–) were calculated. Results showed that: i) %SEQ++ and %SEQ– were balanced regardless of age bin; ii) this conclusion held both at REST and during STAND; iii) %SEQ++ and %SEQ– increased from REST to STAND regardless of age bin; iv) the ageing process decreased %SEQ++ and %SEQ– during STAND, while the percentages were more preserved at REST. This finding might have relevant implications in understanding postural disturbances in advanced age.