Augmentation index assessed by applanation tonometry is elevated in Marfan Syndrome.
BACKGROUND
To examine whether augmentation index (AIx) is increased in Marfan syndrome (MFS) and associated with increased aortic root size, and whether a peripheral-to-central generalised transfer function (GTF) can be applied usefully in MFS.


METHODS
10 MFS patients and 10 healthy controls (matched for sex, age and height) were studied before and after 400 microg sub-lingual GTN. Arterial waveforms were recorded using applanation tonometry. AIx and pulse pressure (PP) were determined for the radial and carotid arteries. Pulse wave velocity (PWV) was measured between carotid and femoral arteries. GTFs were generated to examine the relationship between radial and carotid waveforms.


RESULTS
AIx was greater in MFS compared to controls at radial (mean -31.4 (SD 14.3)% v -50.2(15.6)%, p = 0.003) and carotid (-7.6(11.2)% v -23.7(12.7)%, p = 0.004) sites. Baseline PP at all measurement sites, and PWV, did not differ between subject groups. Multivariate analysis demonstrated that PWV and carotid AIx were positively correlated with aortic root size (p < 0.001 and p = 0.012 respectively), independent of the presence of MFS. PP was not associated with aortic root size. GTN caused similar decreases in AIx in both controls and patients. Significant differences were found in GTFs between MFS and control subjects, which changed following GTN administration. However, when an independent GTF was used to derive carotid waves from radial waves, no differences were found in the degree of error between MFS and controls.


CONCLUSIONS
AIx is sensitive to the vascular abnormalities present in MFS, and may have a role as an adjunct to measurement of central PP and PWV. Differences between MFS and controls in the nature of the peripheral-to-central GTF are present, although have little effect on the pulse contour.
Payne
Rupert A
RA
Centre for Cardiovascular Science, University of Edinburgh, Queen's Medical Research Institute, 47 Little France Crescent, Edinburgh, EH16 4TJ, UK. r.payne@ed.ac.uk
Hilling-Smith
Roland C
RC
Webb
David J
DJ
Maxwell
Simon R
SR
Denvir
Martin A
MA
D000293:Adolescent; D000328:Adult; D001794:Blood Pressure / Q000187:drug effects; D002339:Carotid Arteries / Q000187:drug effects / Q000503:physiopathology; D016022:Case-Control Studies; D004452:Echocardiography; D004548:Elasticity / Q000187:drug effects; D005260:Female; D005583:Fourier Analysis; D006801:Humans; D008297:Male; D008365:Manometry / Q000379:methods*; D008382:Marfan Syndrome / Q000503:physiopathology*; D008875:Middle Aged; D005996:Nitroglycerin / Q000494:pharmacology; D011673:Pulsatile Flow; D012850:Sinus of Valsalva / Q000000981:diagnostic imaging / Q000187:drug effects / Q000473:pathology; D014665:Vasodilator Agents / Q000494:pharmacology; D055815:Young Adult
D014665:Vasodilator Agents; D005996:Nitroglycerin