Adaptation of baroreflex function to increased carotid artery stiffening in patients with transposition of great arteries
Résumé
We have shown before that transposition of great arteries (TGA) is associated with increased carotid artery stiffness. It has been established that stiffening of the barosensory vessel wall results in reduced baroreceptor activation and impaired baroreflex sensitivity. In this study we tested the hypothesis that the increased carotid artery stiffness in TGA patients was associated with reduced cardiovagal baroreflex sensitivity (BRS). We studied 32 TGA-patients aged 9-19 yrs, 12 ± 3 yrs after surgical repair and 32 healthy control subjects matched for age. Carotid artery diastolic diameter and pulsatile distension was determined by echo wall-tracking; carotid blood pressure was measured by tonometry. BRS was measured by spontaneous techniques (BRS seq}, LF gain}) and by the phenylephrine method (BRS phe}). Carotid artery distensibility was markedly reduced in patients as compared with controls (5.6 ± 1.9 vs. 8.7 ± 2.7*10 -3}/mmHg, p < 0.05, unpaired t-test), but baroreflex sensitivity was not different in patients and controls (20.3 ± 14.7 vs. 21.7 ±12.7 for BRS seq}; 13.1 ± 9.2 vs. 10.6 ± 4.5 for LF gain}, and 19.1 ± 8.6 vs. 24.7 ± 7.1 for BRS phe} respectively). Carotid artery elastic function is markedly impaired in patients with TGA, but the increased stiffness of the barosensory vessel wall is not associated with reduced BRS. It appears that attenuation of baroreceptor stimulus due to arterial stiffening may be compensated by other, possibly neural mechanisms, when it exists as a congenital abnormality.
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