Time domain measurement of the vascular and myocardial branches of the baroreflex: A study in physically active versus sedentary individuals

Abstract

This study tests the spontaneous sequence method for the evaluation of the cardiac, vasomotor, and myocardial branches of the baroreflex. Systolic blood pressure (SBP), interbeat interval (IBI), stroke volume (SV), preejection period (PEP), and total peripheral resistance (TPR) were continuously recorded in 33 physically active and 25 sedentary participants at rest and during a mental arithmetic task. Sequences of spontaneous covariation between SBP and IBI (for the cardiac branch), SV and PEP (for the myocardial branch), and TPR (for the vasomotor branch) were located. The slope of the regression line between values in the sequences produced an estimate of baroreflex sensitivity (BRS), and the proportion of progressive SBP changes that elicited reflex modulations yielded an estimate of baroreflex effectiveness (BEI). The active group showed greater BRS in all three branches than the sedentary group. Cardiac and vasomotor BEI decreased during the arithmetic task in the sedentary group but not in the active one. Only cardiac BRS decreased during the arithmetic task. In conclusion, the method appears appropriate for the simultaneous assessment of the three baroreflex branches. The assessment of the vascular branch of the baroreflex may have prognostic relevance in the development of hypertension or other cardiometabolic diseases.

Intracranial Pressure Is a Determinant of Sympathetic Activity

“…In line with the composite nature of baroreflex (Marchi et al, 2016b ; Reyes Del Paso et al, 2017 ) our data pave the way for further work in order to (i) investigate ICP as a new arm of baroreflex, (ii) validate the hypothesis of an intracranial baroreflex, (iii) identify the afferent pathway and the cardiorespiratory integration centers, (iv) demonstrate that ICP modulates sympathetic activity set-point, (v) investigate the role of raised ICP in the pathogenesis of sympathetic over-activity, (vi) explore the possible sympatholytic effect of reducing ICP, and finally (vii) determine whether ICP control, e.g., with a drug or a ventricular shunt, should be clinically relevant in sympathetically-driven diseases.…”

Editorial: Probing the Cardiac Arm of the Baroreflex and Complementary Branches

“…One of the consequences of the view identifying the BR with cBR is the tendency of interpreting modifications of the mean AP experienced during everyday life in spite of homeostatic characteristic of the BR as a result of its noisy nature (Karemaker and Wesseling, 2008). Conversely, the stochastic nature of the BR might be the simple consequence of its complex and composite nature: indeed, since the BR can target several physiological variables including heart rate, sympathetic activity, peripheral resistances, cardiac contractility, and stroke volume just to mention a few (Smyth et al, 1969;Sundlof and Wallin, 1978;Casadei et al, 1992;Kienbaum et al, 2001;Yasumasu et al, 2005;Vaschillo et al, 2012;Borgers et al, 2014;Barbic et al, 2015;Elstad et al, 2015;Hosokawa and Sunagawa, 2016;Reyes del Paso et al, 2017;Porta et al, 2018) and since the functioning of all these branches is weakly correlated as it appears from the weak correlation among BRSs (Rudas et al, 1999;O'Leary et al, 2003;Dutoit et al, 2010;Taylor et al, 2015;Marchi et al, 2016), it is not surprising to observe that mean AP does not always obey to the homeostatic principle. The composite nature of the BR is compatible with the observation that short-term fluctuations of HP are not intimately and always linked to those of SAP (Diaz and Taylor, 2006).…”

Peripheral Resistance Baroreflex During Incremental Bicycle Ergometer Exercise: Characterization and Correlation With Cardiac Baroreflex

“…Baroreflex (BR) is a composite reflex regulating several cardiovascular variables, comprising heart period (HP) ( Smyth et al, 1969 ; Laude et al, 2004 ), sympathetic activity ( Sundlof and Wallin, 1978 ; Rudas et al, 1999 ; Kienbaum et al, 2001 ; Barbic et al, 2015 ; Marchi et al, 2016 ), peripheral resistances (PR) ( Borgers et al, 2014 ; Reyes del Paso et al, 2017 ), parameters associated with cardiac contractility ( Reyes del Paso et al, 2017 ), and stroke volume ( Casadei et al, 1992 ; Yasumasu et al, 2005 ; Vaschillo et al, 2012 ; Reyes del Paso et al, 2017 ), in response to arterial pressure (AP) variations ( Robertson et al, 2012 ). The various arms of the BR are more and more frequently described simultaneously because it has been suggested that the information derived from monitoring different BR components is not fully redundant and, conversely, their simultaneous assessment might provide a more adequate and complete picture of the complexity of the cardiovascular reflex regulation ( Dutoit et al, 2010 ; Borgers et al, 2014 ; Taylor et al, 2015 ; Marchi et al, 2016 ; Porta et al, 2017b ; Reyes del Paso et al, 2017 ). The cardiac BR (cBR), namely the arm of the BR inducing HP changes parallel to those observed in AP ( Smyth et al, 1969 ), is commonly studied in physiological, closed loop, conditions from short recordings (i.e., 5 min) of spontaneous variability of HP and systolic AP (SAP) ( Laude et al, 2004 ).…”

“…However, sBR characterization based on physiological variability is not fully non-invasive like that of cBR: as a matter of fact, sBR requires the invasive recording of sympathetic activity, usually obtained in humans via microneurographic technique by placing an electrode in the peroneal nerve at the fibular head ( Sundlof and Wallin, 1978 ). To circumvent the involvedness of the microneurographic technique and its invasiveness, sBR characterization has been surrogated via the assessment of BR of PR (prBR) ( Borgers et al, 2014 ; Reyes del Paso et al, 2017 ) exploiting the direct link between sympathetic activity and PR ( Charkoudian et al, 2005 ). Usually, the beat-to-beat variability of PR exploited for the prBR characterization is estimated from the analysis of AP curve ( Borgers et al, 2014 ) or via impedance cardiography ( Reyes del Paso et al, 2017 ).…”

“…To circumvent the involvedness of the microneurographic technique and its invasiveness, sBR characterization has been surrogated via the assessment of BR of PR (prBR) ( Borgers et al, 2014 ; Reyes del Paso et al, 2017 ) exploiting the direct link between sympathetic activity and PR ( Charkoudian et al, 2005 ). Usually, the beat-to-beat variability of PR exploited for the prBR characterization is estimated from the analysis of AP curve ( Borgers et al, 2014 ) or via impedance cardiography ( Reyes del Paso et al, 2017 ).…”