Two-dimensional autoregressive analysis of carotid artery blood flow waveform in children with isolated atrial septal defect

Background: The aim of the present study was to analyze the carotid artery blood flow waveform, using a two-dimensional autoregressive modeling approa ch and component analysis, and to determine the relation between cardiac co ntractility, peripheral and cerebral circulation and characteristic values of component activities of carotid artery blood flow waveform in patients w ith atrial septal defect (ASD), with or without congestive heart failure. Methods and Results: We analyzed the carotid artery blood flow waveform of nine patients with ASD and 35 normal controls using a two-dimensional autor egressive modeling approach. The component of impulse response was divided into six groups according to the damping frequency: (i) group I, 0 Hz; (ii) group II, 1-5 Hz; (iii) group III, 5-8 Hz; (iv) group IV, 8-13 Hz; (v) gro up V, 13-17 Hz and (vi) group VI, > 17 Hz. The decrease of impulse response power-density in patients of groups I, II, III and IV and the prolongation of damping time for patients in groups I and II were particularly noticeab le in two ASD patients, whose pulmonary to systemic blood flow ratio was mo re than 2.7 and whose left ventricular stroke volume was less than 33.1 mL/ m(2). The power-density of groups I and II varied with cardiac contractilit y and the power-density of groups III and IV varied with cerebral circulati on. In contrast, the damping time of groups I and II changed with the refle ction velocity from the position of arterial reflection against blood flow from left ventricle. Conclusions: These results may be influenced by the decrease in left ventri cular stroke volume and velocity in arterial reflection.