Proceedings of The Physiological Society
University of Cambridge (2004) J Physiol 555P, C26
Cardiovascular autonomic dysfunction in neonates with coarctation of the aorta (CoA)
J.W. Polson, N. McCallion, M.A. Tooley, G. Thorne, S. Kasparov, J.F.R. Paton and A.R. Wolf
Division of Cardiac, Anaesthetic and Radiological Sciences & * Department of Physiology, Bristol Heart Institute, University of Bristol, Bristol, UK
CoA is a common congenital malformation with variable narrowing of the proximal descending thoracic aorta. Surgical correction is the accepted medical treatment, and delayed repair is associated with abnormalities of arterial pressure (AP) homeostasis and early death. It was hoped that neonatal repair would prevent later cardiovascular complications, but recent data have indicated that despite an early and successful anatomic repair, 30 % of patients still subsequently develop hypertension (O'Sullivan et al. 2002). The aetiology is unclear, but may involve changes in cardiovascular autonomic regulation during the perinatal period. Two important indices of cardiovascular autonomic function are baroreceptor reflex sensitivity (BRS) and heart rate variability (HRV). Neither of these have been examined in the neonate with CoA. In order to understand the development of hypertension in patients with CoA, we have examined BRS and HRV in neonates at first presentation.
After local ethical committee approval and informed parental consent we recruited 6 neonates undergoing elective CoA repair and compared them with 10 healthy newborn infants. AP was measured non-invasively using photoplethysmography by means of adapting a Portapres (Finapres Medical Systems, Netherlands) for use in infants by placing the cuff around the infant's right wrist. Accuracy of the recording was confirmed initially by comparison with measurements made using an arterial line. ECG was recorded using a standard three lead configuration. AP and ECG waveforms were sampled at 1-5 kHz and recorded continuously for 20-30 min while infants were in active sleep. Spontaneous BRS was measured using a modification of the time sequence method of Oosting et al. (1997). HRV was examined using standard time domain measurements. Results are expressed as mean ± S.E.M. All infants were under 5 weeks of age.
We found that there was good correlation between Portapres and arterial line measurements of AP (mean 53.2 ± 0.5 v 55.8 ± 0.2 mmHg, respectively), although pulse pressure was lower on Portapres measurements (30.2 ± 1.2 v 38.7 ± 2.7 mmHg). Systolic AP was higher in CoA than controls (79.5 ± 4.6 v 68.8 ± 2.4 mmHg). BRS was reduced by 37 % in CoA compared to controls (9.1 ± 1.9 v 14.4 ± 1.6 ms/mmHg, respectively), and HRV was similarly reduced: the range over which 95 % of R-R intervals fell was 89.9 ± 11.2 v 148.0 ± 9.1 ms, and the standard deviation of the R-R intervals was 22.5 ± 2.8 v 37.2 ± 2.5.
These data indicate that cardiovascular autonomic regulation is abnormal in infants with preoperative CoA.
We gratefully acknowledge the support of B. Braun Medical Ltd.
Where applicable, experiments conform with Society ethical requirements