title: The arterial reservoir pressure increases with aging and is the major determinant of the aortic augmentation index.
abstract: The augmentation index predicts cardiovascular mortality and is usually explained as a distally reflected wave adding to the forward wave generated by systole. We propose that the capacitative properties of the aorta (the arterial reservoir) also contribute significantly to the augmentation index and have calculated the contribution of the arterial reservoir, independently of wave reflection, and assessed how these contributions change with aging. In 15 subjects (aged 53 +/- 10 yr), we measured pressure and Doppler velocity simultaneously in the proximal aorta using intra-arterial wires. We calculated the components of augmentation pressure in two ways: 1) into forward and backward (reflected) components by established separation methods, and 2) using an approach that accounts for an additional reservoir component. When the reservoir was ignored, augmentation pressure (22.7 +/- 13.9 mmHg) comprised a small forward wave (peak pressure = 6.5 +/- 9.4 mmHg) and a larger backward wave (peak pressure = 16.2 +/- 7.6 mmHg). After we took account of the reservoir, the contribution to augmentation pressure of the backward wave was reduced by 64% to 5.8 +/- 4.4 mmHg (P < 0.001), forward pressure was negligible, and reservoir pressure was the largest component (peak pressure = 19.8 +/- 9.3 mmHg). With age, reservoir pressure increased progressively (9.9 mmHg/decade, r = 0.69, P < 0.001). In conclusion, the augmentation index is principally determined by aortic reservoir function and other elastic arteries and only to a minor extent by reflected waves. Reservoir function rather than wave reflection changes markedly with aging, which accounts for the age-related changes in the aortic pressure waveform.
authors.affiliation: International Centre for Circulatory Health, St. Mary's Hospital & Imperial College, 59-61 N. Wharf Rd., Paddington, London, W2 1LA, UK. justin.davies@imperial.ac.uk
authors.forename: Justin E
authors.initials: JE
authors.lastname: Davies
authors.forename: John
authors.initials: J
authors.lastname: Baksi
authors.forename: Darrel P
authors.initials: DP
authors.lastname: Francis
authors.forename: Nearchos
authors.initials: N
authors.lastname: Hadjiloizou
authors.forename: Zachary I
authors.initials: ZI
authors.lastname: Whinnett
authors.forename: Charlotte H
authors.initials: CH
authors.lastname: Manisty
authors.forename: Jazmin
authors.initials: J
authors.lastname: Aguado-Sierra
authors.forename: Rodney A
authors.initials: RA
authors.lastname: Foale
authors.forename: Iqbal S
authors.initials: IS
authors.lastname: Malik
authors.forename: John V
authors.initials: JV
authors.lastname: Tyberg
authors.forename: Kim H
authors.initials: KH
authors.lastname: Parker
authors.forename: Jamil
authors.initials: J
authors.lastname: Mayet
authors.forename: Alun D
authors.initials: AD
authors.lastname: Hughes
mesh_terms: D000328:Adult; D000368:Aged; D000375:Aging / Q000502:physiology*; D001011:Aorta / Q000502:physiology*; D001783:Blood Flow Velocity / Q000502:physiology; D001794:Blood Pressure / Q000502:physiology*; D002318:Cardiovascular Diseases / Q000453:epidemiology / Q000503:physiopathology; D017023:Coronary Angiography; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D011673:Pulsatile Flow / Q000502:physiology*; D012307:Risk Factors