Evaluation of the impact of surgical aortic valve replacement on short-term cardiovascular and cerebrovascular controls through spontaneous variability analysis.

Alberto Porta,Francesca Gelpi,Beatrice De Maria,Vlasta Bari,Edward Callus,Beatrice Cairo,Marianna Volpe,Valentina Fiolo,Marco Ranucci,Angela Fantinato,Enrico Giuseppe Bertoldo,Raffaella Molfetta,Carlo De Vincentiis,Vincenzo Lionetti

doi:10.1371/journal.pone.0243869

Alberto Porta, Francesca Gelpi + Show 12 more

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https://doi.org/10.1371/journal.pone.0243869

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Abstract

We assessed the effect of surgical aortic valve replacement (SAVR) on cardiovascular and cerebrovascular controls via spontaneous variability analyses of heart period, approximated as the temporal distance between two consecutive R-wave peaks on the electrocardiogram (RR), systolic, diastolic and mean arterial pressure (SAP, DAP and MAP) and mean cerebral blood flow (MCBF). Powers in specific frequency bands, complexity, presence of nonlinear dynamics and markers of cardiac baroreflex and cerebral autoregulation were calculated. Variability series were acquired before (PRE) and after (POST) SAVR in 11 patients (age: 76±5 yrs, 7 males) at supine resting and during active standing. Parametric spectral analysis was performed based on the autoregressive model. Complexity was assessed via a local nonlinear prediction approach exploiting the k-nearest-neighbor strategy. The presence of nonlinear dynamics was checked by comparing the complexity marker computed over the original series with the distribution of the same index assessed over a set of surrogates preserving distribution and power spectral density of the original series. Cardiac baroreflex and cerebral autoregulation were estimated by assessing the transfer function from SAP to RR and from MAP to MCBF and squared coherence function via the bivariate autoregressive approach. We found that: i) orthostatic challenge had no effect on cardiovascular and cerebrovascular control markers in PRE; ii) RR variance was significantly reduced in POST; iii) complexity of SAP, DAP and MAP variabilities increased in POST with a greater likelihood of observing nonlinear dynamics over SAP compared to PRE at supine resting; iv) the amplitude of MCBF variations and MCBF complexity in POST remained similar to PRE; v) cardiac baroreflex sensitivity decreased in POST, while cerebrovascular autoregulation was preserved. SAVR induces important changes of cardiac and vascular autonomic controls and baroreflex regulation in patients exhibiting poor reactivity of cardiovascular regulatory mechanisms, while cerebrovascular autoregulation seems to be less affected.

Highlights

Since sympathetic activation and vagal withdrawal lead to the decrease of the variability of heart period, approximated as the temporal distance between two consecutive R-wave peaks on the electrocardiogram (RR), and to the increase of the fluctuations of systolic arterial pressure (SAP), the RR and SAP variances have been exploited to infer vagal and sympathetic neural controls [1,2,3,4,5,6]
Regardless of the experimental condition (i.e. rest in supine position (REST) or STAND), μRR significantly decreased in POST compared to PRE. σ2RR decreased and μDAP increased during POST with respect to PRE but the rise was significant solely at REST and during STAND respectively
The sole time domain index that was able to highlight a significant effect of the orthostatic challenge was μDAP that increased during STAND compared to REST in the POST session

Summary

Introduction

Since sympathetic activation and vagal withdrawal lead to the decrease of the variability of heart period, approximated as the temporal distance between two consecutive R-wave peaks on the electrocardiogram (RR), and to the increase of the fluctuations of systolic arterial pressure (SAP), the RR and SAP variances have been exploited to infer vagal and sympathetic neural controls [1,2,3,4,5,6]. Spectral analysis allowed a more precise link of RR and SAP variabilities with the state of the autonomic nervous system given that oscillations in the high frequency (HF, from 0.15 to 0.4 Hz) band of the RR series are associated to vagal control directed to the sinus node [1,2,3,4,5,6], while those in the low frequency (LF, from 0.04 to 0.15 Hz) band of the SAP series are linked to sympathetic control directed to the vessels [4,5,6]. Complexity and nonlinear content of the RR and SAP variability series are frequently explored to gain insight into peculiar features of autonomic regulatory mechanisms that cannot be fully described by power spectral density [7,8,9,10,11,12,13]. Complexity of the cardiac control is reduced during sympathetic activation and vagal withdrawal [7, 8]. The different response of regulatory mechanisms to positive or negative SAP variations and circuits imposing a certain degree of cardiorespiratory phase coupling might play an important role in producing nonlinear RR variability patterns [14,15,16]

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