Baroreflex Sensitivity in Children, Adolescents, and Young Adults with Essential and White-Coat Hypertension

Abstract

Hypertension, which is a common cardiovascular disease in adults, could originate in childhood. The aim of the study was to show differences in baroreflex sensitivity and short-term blood-pressure variability between healthy and hypertensive children, adolescents and young adults, and those with white-coat effect with respect to obesity. We examined 54 subjects (11-21 years) who had repeatedly high causal blood pressure. Basing on 24-hour blood pressure monitoring, the subjects were divided into groups: 24 subjects with hypertension (Hy) and 30 subjects with white-coat effect (WhC). Hy and WhC subjects were compared with age-matched healthy controls in a ratio of 1 : 2 for both groups: 48 controls for hypertensive subjects (CoHy) and 60 for subjects with white-coat effect (CoWhC). Totally, 162 subjects were studied. Systolic blood pressure (SBP) and inter-beat intervals (IBI) were recorded in all subjects for 5 min (Finapres, metronome controlled breathing at a frequency of 0.33 Hz). The power spectra of SBP and IBI were calculated. Indices of baroreflex sensitivity (BRS [ms/mmHg] and BRSf [mHz/mmHg]) were determined by the cross-spectral method. The SBP variability was determined as SBP spectral power in the range of 10-second rhythm (SBP_0.1Hz). The body mass index (BMI) was significantly higher in both Hy and WhC compared with their controls (Hy vs. CoHy; WhC vs. CoWhC: 24.6 ± 6.0 kg/m² vs. 20.4 ± 2.8 kg/m², p < 0.001; 23.2 ± 5.9 kg/m² vs. 20.3 ± 2.6 kg/m², p < 0.05). BRS was significantly decreased in both groups (Hy vs. CoHy; WhC vs. CoWhC: 6.0 ± 2.7 ms/mmHg vs. 9.5 ± 3.9 ms/mmHg, p < 0.001; 7.2 ± 3.1 ms/mmHg vs. 10.9 ± 6.2 ms/mmHg, p < 0.01), and BRSf as well (Hy vs. CoHy; WhC vs. CoWhC: 10.8 ± 4.6 mHz/mmHg vs. 16.2 ± 6.1 mHz/mmHg, p < 0.001; 13.0 ± 4.9 mHz/mmHg vs. 18.3 ± 8.7 mHz/mmHg, p < 0.01). The decrease of baroreflex sensitivity was linked with the increase in the variability of SBP_0.1Hz, which was significant in hypertensives only (Hy vs. CoHy; WhC vs. CoWhC: 142 ± 96 mmHg²/Hz vs. 94 ± 83 mmHg²/Hz, p < 0.01; 121 ± 131 mmHg²/Hz vs. 107 ± 98 mmHg²/Hz). Conclusion: The mild increase of BMI was associated with white-coat effect and a BRS and BRSf decrease. The greater increase of BMI was associated with hypertension and a deeper BRS and BRSf decrease. This greater decrease of BRS and BRSf in hypertensives was linked with the increased SBP-variability.

Zusammenfassung

Hypertonie ist eine häufige Erkrankung bei Erwachsenen und beginnt oft im Kindesalter. Das Ziel unserer Studie war, Unterschiede in der Baroreflexsensitivität und der kurzzeitigen Blutdruckvariabilität zwischen gesunden, hypertonen Individuen und Probanden mit „Weißkittelhypertonie” im Kindes-, Jugendlichen- bzw. jungen Erwachsenenalter mit besonderem Augenmerk auf bestehende Obesität zu evaluieren. Wir untersuchten 54 Personen im Alter von 11 bis 21 Jahren, die während Wiederholungsmessungen einen hohen Blutdruck hatten. Aufgrund der 24-Stunden-Blutdruckmessung wurden die Versuchspersonen in zwei Gruppen unterteilt: 24 Personen mit Hypertonie (Hy) und 30 Personen mit „Weißkittelhypertonie” (WhC). Beide Gruppen wurden mit gesunden Probanden desselben Alters im Verhältnis 1 : 2 verglichen: 48 Kontrollpersonen für Hypertoniker (CoHy) und 60 Kontrollpersonen für die Gruppe „Weißkittelhypertonie” (CoWhC); insgesamt wurden 162 Personen untersucht. Der systolische Blutdruck (SBP) und die Zwischenschlagintervalle (IBI) wurden 5 Minuten bei jeder Person aufgenommen (Finapres, metronomkontrollierte Atmung mit einer Frequenz von 0,33 Hz). Die Leistungsspektren von SBP und IBI wurden kalkuliert. Mittels der Cross-Spektralmethode wurden die Indizes der Baroreflexsensitivität (BRS [ms/mmHg] und BRSf [mHz/mmHg]) festgestellt. Die SBP-Variabilität wurde als SBP-Spektralleistung im Frequenzbereich eines 10-Sekunden-Rhythmus (SBP_0.1Hz) definiert. Der BMI (Bodymass-Index) war in beiden Gruppen (Hy und WhC) im Vergleich zu den Kontrollgruppen signifikant erhöht (Hy vs. CoHy; WhC vs. CoWhC: 24,6 ± 6,0 kg/m² vs. 20,4 ± 2,8 kg/m², p < 0,001; 23,2 ± 5,9 kg/m² vs. 20,3 ± 2,6 kg/m², p < 0,05). Demgegenüber zeigte sich die BRS in beiden Gruppen signifikant vermindert (Hy vs. CoHy; WhC vs. CoWhC: 6,0 ± 2,7 ms/mmHg vs. 9,5 ± 3,9 ms/mmHg, p < 0,001; 7,2 ± 3,1 ms/mmHg vs. 10,9 ± 6,2 ms/mmHg, p < 0,01), ebenfalls die BRSf (Hy vs. CoHy; WhC vs. CoWhC: 10,8 ± 4,6 mHz/mmHg vs. 16,2 ± 6,1 mHz/mmHg, p < 0,001; 13,0 ± 4,9 mHz/mmHg vs. 18,3 ± 8,7 mHz/mmHg, p < 0,01). Die Verminderung der Baroreflexsensitivität ging mit einer SBP_0.1Hz-Erhöhung einher, die nur bei den Hypertonikern eine Signifikanz erreichte (Hy vs. CoHy; WhC vs. CoWhC: 142 ± 96 mmHg²/Hz vs. 94 ± 83 mmHg²/Hz, p < 0,01; 121 ± 131 mmHg²/Hz vs. 107 ± 98 mmHg²/Hz). Schlussfolgerung: Eine milde BMI-Erhöhung geht oft mit dem „Weißkitteleffekt” und einer Verminderung von BRS sowie BRSf einher, eine stärkere Erhöhung des BMI ist mit Hypertonie und einer größeren Verminderung von BRS und BRSf vergesellschaftet. Diese bei Hypertonikern größere Verminderung von BRS und BRSf war an die SBP_0.1Hz-Erhöhung gekoppelt.

Baroreflex sensitivity - white-coat hypertension - body mass index - adolescents

Baroreflexsensitivität - Weißkittelhypertonie - Bodymass-Index - Jugendliche

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