TY - JOUR
T1 - Quantification of wave reflection in the human aorta from pressure alone
T2 - A proof of principle
AU - Westerhof, Berend E.
AU - Guelen, Ilja
AU - Westerhof, Nico
AU - Karemaker, John M.
AU - Avolio, Alberto
PY - 2006/10
Y1 - 2006/10
N2 - Wave reflections affect the proximal aortic pressure and flow waves and play a role in systolic hypertension. A measure of wave reflection, receiving much attention, is the augmentation index (AI), the ratio of the secondary rise in pressure and pulse pressure. AI can be limiting, because it depends not only on the magnitude of wave reflection but also on wave shapes and timing of incident and reflected waves. More accurate measures are obtainable after separation of pressure in its forward (Pf) and reflected (Pb) components. However, this calculation requires measurement of aortic flow. We explore the possibility of replacing the unknown flow by a triangular wave, with duration equal to ejection time, and peak flow at the inflection point of pressure (F) and, for a second analysis, at 30% of ejection time (F). Wave form analysis gave forward and backward pressure waves. Reflection magnitude (RM) and reflection index (RI) were defined as RM=Pb/Pf and RI=Pb/(Pf+Pb), respectively. Healthy subjects, including interventions such as exercise and Valsalva maneuvers, and patients with ischemic heart disease and failure were analyzed. RMs and RIs using F and F were compared with those using measured flow (F). Pressure and flow were recorded with high fidelity pressure and velocity sensors. Relations are: RM=0.82RM+0.06 (R=0.79; n=24), RM=0.79RM+0.08 (R=0.85; n=29) and RI=0.89RI+0.02 (R=0.81; n=24), RI=0.83RI+0.05 (R=0.88; n=29). We suggest that wave reflection can be derived from uncalibrated aortic pressure alone, even when no clear inflection point is distinguishable and AI cannot be obtained. Epidemiological studies should establish its clinical value.
AB - Wave reflections affect the proximal aortic pressure and flow waves and play a role in systolic hypertension. A measure of wave reflection, receiving much attention, is the augmentation index (AI), the ratio of the secondary rise in pressure and pulse pressure. AI can be limiting, because it depends not only on the magnitude of wave reflection but also on wave shapes and timing of incident and reflected waves. More accurate measures are obtainable after separation of pressure in its forward (Pf) and reflected (Pb) components. However, this calculation requires measurement of aortic flow. We explore the possibility of replacing the unknown flow by a triangular wave, with duration equal to ejection time, and peak flow at the inflection point of pressure (F) and, for a second analysis, at 30% of ejection time (F). Wave form analysis gave forward and backward pressure waves. Reflection magnitude (RM) and reflection index (RI) were defined as RM=Pb/Pf and RI=Pb/(Pf+Pb), respectively. Healthy subjects, including interventions such as exercise and Valsalva maneuvers, and patients with ischemic heart disease and failure were analyzed. RMs and RIs using F and F were compared with those using measured flow (F). Pressure and flow were recorded with high fidelity pressure and velocity sensors. Relations are: RM=0.82RM+0.06 (R=0.79; n=24), RM=0.79RM+0.08 (R=0.85; n=29) and RI=0.89RI+0.02 (R=0.81; n=24), RI=0.83RI+0.05 (R=0.88; n=29). We suggest that wave reflection can be derived from uncalibrated aortic pressure alone, even when no clear inflection point is distinguishable and AI cannot be obtained. Epidemiological studies should establish its clinical value.
KW - Aorta
KW - Blood flow
KW - Blood flow velocity
KW - Blood pressure
KW - Pulse
UR - http://www.scopus.com/inward/record.url?scp=33750590779&partnerID=8YFLogxK
U2 - 10.1161/01.HYP.0000238330.08894.17
DO - 10.1161/01.HYP.0000238330.08894.17
M3 - Article
VL - 48
SP - 595
EP - 601
JO - Hypertension
JF - Hypertension
SN - 0194-911X
IS - 4
ER -