Carotid artery pulse wave time characteristics to quantify ventriculoarterial responses to orthostatic challenge.
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.
Reesink
Koen D
KD
Department of Biophysics, CARIM, Maastricht University, PO Box 616, 6200 MD Maastricht, The Netherlands. k.reesink@bf.unimaas.nl
Hermeling
Evelien
E
Hoeberigs
M Christianne
MC
Reneman
Robert S
RS
Hoeks
Arnold P G
AP
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*