title: Carotid artery pulse wave time characteristics to quantify ventriculoarterial responses to orthostatic challenge.
abstract: Central blood pressure waveforms contain specific features related to cardiac and arterial function. We investigated posture-related changes in ventriculoarterial hemodynamics by means of carotid artery (CA) pulse wave analysis. ECG, brachial cuff pressure, and common CA diameter waveforms (by M-mode ultrasound) were obtained in 21 healthy volunteers (19-30 yr of age, 10 men and 11 women) in supine and sitting positions. Pulse wave analysis was based on a timing extraction algorithm that automatically detects acceleration maxima in the second derivative of the CA pulse waveform. The algorithm enabled determination of isovolumic contraction period (ICP) and ejection period (EP): ICP=43+/-8 (SD) ms (4-ms precision), and EP=302+/-16 (SD) ms (5-ms precision). Compared with the supine position, in the sitting position diastolic blood pressure (DBP) increased by 7+/-4 mmHg (P<0.001) and R-R interval decreased by 49+/-82 ms (P=0.013), reflecting normal baroreflex response, whereas EP decreased to 267+/-19 ms (P<0.001). Shortening of EP was significantly correlated to earlier arrival of the lower body peripheral reflection wave (r2=0.46, P<0.001). ICP increased by 7+/-7 ms (P<0.001), the ICP-to-EP ratio increased from 14+/-3% (supine) to 19+/-3% (P<0.001) and the DBP-to-ICP ratio decreased by 7% (P=0.023). These results suggest that orthostasis decreases left ventricular output as a result of arterial wave reflections and, presumably, reduced cardiac preload. We conclude that CA ultrasound and pulse wave analysis enable noninvasive quantification of ventriculoarterial responses to changes in posture.
authors.affiliation: Department of Biophysics, CARIM, Maastricht University, PO Box 616, 6200 MD Maastricht, The Netherlands. k.reesink@bf.unimaas.nl
authors.forename: Koen D
authors.initials: KD
authors.lastname: Reesink
authors.forename: Evelien
authors.initials: E
authors.lastname: Hermeling
authors.forename: M Christianne
authors.initials: MC
authors.lastname: Hoeberigs
authors.forename: Robert S
authors.initials: RS
authors.lastname: Reneman
authors.forename: Arnold P G
authors.initials: AP
authors.lastname: Hoeks
mesh_terms: D000328:Adult; D001794:Blood Pressure / Q000502:physiology*; D002339:Carotid Arteries / Q000000981:diagnostic imaging / Q000502:physiology*; D003198:Computer Simulation; D005260:Female; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods; D008297:Male; D008955:Models, Cardiovascular; D011187:Posture / Q000502:physiology*; D011673:Pulsatile Flow / Q000502:physiology*; D018667:Tilt-Table Test; D014463:Ultrasonography; D016277:Ventricular Function, Left / Q000502:physiology*