P9.03 Regional Age-Related Changes in Aortic Pulse Wave Velocity and Systolic Diameter Measured Using Magnetic Resonance Imaging

Abstract

Aortic pulse wave velocity (PWV) is an independent predictor of cardiovascular risk. However, PWV is usually determined between the carotid and femoral sites, ignoring the proximal ascending aorta which may stiffen most with age. We tested this hypothesis by assessing regional PWV and aortic diameter along the entire aorta using MRI.

147 healthy subjects aged 18-85 years, free of cardiovascular disease and medication, were recruited from the ACCT Study. A PCMRI sequence (1.5 T scanner, GE) was then performed in all subjects at 5 aortic levels: ascending (L1), descending (L2), diaphragm (L3), 3 cm above the bifurcation (L5), and mid way between L3 and L5 (L4). Systolic diameter was measured at each level. PWV (PWV_MRI) was then determined in 4 aortic regions: the arch (R1), the thoracic-descending (R2), mid-descending (R3) and abdominal (R4).

Average PWV_MRI values increased from R1 to R4 (4.6 ± 1.5m/s, 5.5 ± 2.0m/s, 5.7 ± 2.3m/s, 6.1 ± 2.9m/s, respectively) and was not different between genders. The greatest age-related increase in PWV_MRI occurred in the abdominal aorta (R4) (0.9 m/s per decade, P< 0.001) followed by R2 (0.7 m/s,P< 0.001), R3 (0.6 m/s, P< 0.001) and R1 (0.4 m/s, P< 0.001). The average aortic diameters for L1 to L5 were 3.1 ± 0.4 cm, 2.3 ± 0.3 cm, 2.1 ± 0.3 cm, 1.9 ± 0.2 cm, and 1.7 ± 0.2 cm respectively. The aortic diameter at each level was correlated with age (r = 0.41, 0.50, 0.40, 0.43, and 0.25 for L1–L5 respectively, P < 0.001 for all values) with the greatest age-related increase occurring at L1 (0.093 mm/decade, P < 0.001).

Age-related increases in arterial stiffness are greatest in the abdominal aorta whereas the greatest increase in diameter occurred in the ascending aorta.