We tested an innovative approach for estimating baroreflex sensitivity (BRS) from the gain function between spontaneous oscillations of systolic arterial pressure (SAP) and heart period (HP). The major goal was to assess the practical implications of abandoning the classical coherence criterion (⩾0.5) as regards measurability of BRS, and agreement with values of BRS obtained using the phenylephrine test (Phe-BRS). We studied 19 normal subjects, 44 patients with a history of previous myocardial infarction (MI) and 45 patients with chronic heart failure (CHF). The experimental protocol included recording of SAP and HP for 10min of supine rest, and evaluation of Phe-BRS. From resting SAP and HP, the gain and coherence functions were computed. The new BRS index was obtained in all subjects by averaging the gain function over the whole low-frequency band (0.04-0.15Hz) (whole-band average BRS, WBA-BRS). WBA-BRS was 7.4 (5.8-10.8)ms/mmHg [median (25th-75th percentile)] in normal controls, 3.1 (1.4-5.4)ms/mmHg in MI patients (P<0.001 compared with normals) and 5.0 (3.2-6.9)ms/mmHg in CHF patients (P<0.01 compared with normals). Using the coherence criterion, BRS could be measured in only 43% and 49% of MI and CHF patients respectively, and the proportion of the low-frequency band contributing to the measurement was 21% (14-47%) and 29% (16-35%) respectively. The correlation between WBA-BRS and Phe-BRS was 0.47, 0.63 and 0.36 in the normal, MI and CHF groups respectively (all P<0.001). The relative bias of WBA-BRS was -5.2ms/mmHg (P<0.001) in normals, -1.4ms/mmHg (P = 0.004) in MI patients and -1.0ms/mmHg (P = 0.11) in CHF patients. The limits of agreement were -13 to 2.6, -7.4 to 4.6 and -9.3 to 7.3ms/mmHg in the normal, MI and CHF groups respectively. Thus the WBA-BRS method standardizes the computation of BRS among subjects, and dramatically increases its measurability in subjects with pathology compared with the classical spectral technique based on the coherence criterion. Compared with Phe-BRS, WBA-BRS tends to give negatively biased results. The correlation and the magnitude of the limits of agreement between the two methods are similar to those observed previously using coherence-based spectral methods.
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June 20 2002
Measuring baroreflex sensitivity from the gain function between arterial pressure and heart period
Gian Domenico PINNA;
*Fondazione S. Maugeri, Clinica del Lavoro e della Riabilitazione, IRCCS Istituto Scientifico di Montescano, 27040 Montescano (PV), Italy
Correspondence: Dr Gian Domenico Pinna (e-mail [email protected]).
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Roberto MAESTRI;
Roberto MAESTRI
*Fondazione S. Maugeri, Clinica del Lavoro e della Riabilitazione, IRCCS Istituto Scientifico di Montescano, 27040 Montescano (PV), Italy
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Grzegorz RACZAK;
Grzegorz RACZAK
†II Department of Cardiology, Medical University, Gdansk, Poland
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Maria Teresa LA ROVERE
Maria Teresa LA ROVERE
*Fondazione S. Maugeri, Clinica del Lavoro e della Riabilitazione, IRCCS Istituto Scientifico di Montescano, 27040 Montescano (PV), Italy
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Publisher: Portland Press Ltd
Received:
August 22 2001
Revision Received:
January 11 2002
Accepted:
April 18 2002
Online ISSN: 1470-8736
Print ISSN: 0143-5221
The Biochemical Society and the Medical Research Society © 2002
2002
Clin Sci (Lond) (2002) 103 (1): 81–88.
Article history
Received:
August 22 2001
Revision Received:
January 11 2002
Accepted:
April 18 2002
Citation
Gian Domenico PINNA, Roberto MAESTRI, Grzegorz RACZAK, Maria Teresa LA ROVERE; Measuring baroreflex sensitivity from the gain function between arterial pressure and heart period. Clin Sci (Lond) 1 July 2002; 103 (1): 81–88. doi: https://doi.org/10.1042/cs1030081
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