Article

Age-related changes of regional pulse wave velocity in the descending aorta using Fourier velocity encoded M-mode

Department of Radiology, University of Cambridge, Addenbrooke's Hospital, Cambridge, United Kingdom.
Magnetic Resonance in Medicine (Impact Factor: 3.4). 01/2011; 65(1):261-8. DOI: 10.1002/mrm.22590
Source: PubMed

ABSTRACT Aortic pulse wave velocity (PWV) is an independent determinant of cardiovascular risk. Although aortic stiffening with age is well documented, the interaction between aging and regional aortic PWV is still a debated question. We measured global and regional PWV in the descending aorta of 56 healthy subjects aged 25-76 years using a one-dimensional, interleaved, Fourier velocity encoded pulse sequence with cylindrical excitation. Repeatability across two magnetic resonance examinations (n = 19) and accuracy against intravascular pressure measurements (n = 4) were assessed. The global PWV was found to increase nonlinearly with age. The thoracic aorta was found to stiffen the most with age (PWV [thoracic, 20-40 years] = 4.7 ± 1.1 m/s; PWV [thoracic, 60-80 years] = 7.9 ± 1.5 m/s), followed by the mid- (PWV [mid-abdominal, 20-40 years] = 4.9 ± 1.3 m/s; PWV [mid-abdominal, 60-80 years] = 7.4 ± 1.9 m/s) and distal abdominal aorta (PWV [distal abdominal, 20-40 years] = 4.8 ± 1.4 m/s; PWV [distal abdominal, 60-80 years] = 5.7 ± 1.4 m/s). Good agreement was found between repeated magnetic resonance measurements and between magnetic resonance PWVs and the gold-standard. Fourier velocity encoded M-mode allowed to measure global and regional PWV in the descending aorta. There was a preferential stiffening of the thoracic aorta with age, which may be due to progressive fragmentation of elastin fibers in this region.

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    • "Nevertheless, other studies failed to prove the prognostic value of PWV in elderly populations or subjects with increased arterial stiffness (Megnien, Simon, Denarie, Del-Pino, Gariepy, Segond et al. 1998; Protogerou, Safar, Iaria, Safar, Le Dudal, Filipovsky et al. 2007; Verwoert, Elias-Smale, Rizopoulos, Koller, Steyerberg, Hofman et al. 2012). The rationale behind the limited prognostic value of PWV in the aforementioned studies may be due to: (i) the non-linear association between PWV and compliance as previously suggested (Vardoulis et al. 2012), (ii) the non-linear association between PWV and age (Taviani et al. 2011), or (iii) decrease of blood pressure (BP) in the frailest subjects and BP-dependence of PWV. "
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    ABSTRACT: Aortic stiffness, assessed by carotid-to-femoral pulse wave velocity (PWV), often fails to predict cardiovascular (CV) risk and mortality in the very elderly. This may be due to the non-linear association between PWV and compliance or to blood pressure decrease in the frailest subjects. Total arterial compliance (C T) is the most relevant arterial property regarding CV function, compared to local or regional arterial stiffness. A new method for C T estimation, based on PWV, was recently proposed. We aimed to investigate the value of C T to predict all-cause mortality at the elderly. PWV was estimated in 279 elderly subjects (85.5 ± 7.0 years) who were followed up for a mean period of 12.8 ± 6.3 months. C T was estimated by the formula C T = k × PWV(-2); coefficient k is body-size dependent based on previous in silico simulations. Herein, k was adjusted for body mass index (BMI) with a 10 % change in BMI corresponding to almost 11 % change in k. For a reference BMI = 26.2 kg/m(2), k = 37. Survivors (n = 185) and non-survivors (n = 94) had similar PWV (14.2 ± 3.6 versus 14.9 ± 3.8 m/s, respectively; p = 0.139). In contrast, non-survivors had significantly lower C T than survivors (0.198 ± 0.128 versus 0.221 ± 0.1 mL/mmHg; p = 0.018). C T was a significant predictor of mortality (p = 0.022, odds ratio = 0.326), while PWV was not (p = 0.202), even after adjustment for gender, mean pressure and heart rate. Age was an independent determinant of C T (p = 0.016), but not of PWV. C T, estimated by a novel method, can predict all-cause mortality in the elderly. C T may be more sensitive arterial biomarker than PWV regarding CV risk assessment.
    Age 05/2014; 36(3). DOI:10.1007/s11357-014-9661-0 · 3.45 Impact Factor
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    • "Furthermore, it is known that the aorta stiffens with age. It was shown that global PWV increases in a nonlinear fashion with age and is most pronounced in the thoracic aorta [28], probably because of cumulative degradation of elastin fibers with age [29] that are most abundant in the thoracic part of the aorta. "
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    ABSTRACT: The Bramwell-Hill model describes the relation between vascular wall stiffness expressed in aortic distensibility and the pulse wave velocity (PWV), which is the propagation speed of the systolic pressure wave through the aorta. The main objective of this study was to test the validity of this model locally in the aorta by using PWV-assessments based on in-plane velocity-encoded cardiovascular magnetic resonance (CMR), with invasive pressure measurements serving as the gold standard. Seventeen patients (14 male, 3 female, mean age ± standard deviation = 57 ± 9 years) awaiting cardiac catheterization were prospectively included. During catheterization, intra-arterial pressure measurements were obtained in the aorta at multiple locations 5.8 cm apart. PWV was determined regionally over the aortic arch and locally in the proximal descending aorta. Subsequently, patients underwent a CMR examination to measure aortic PWV and aortic distention. Distensibility was determined locally from the aortic distension at the proximal descending aorta and the pulse pressure measured invasively during catheterization and non-invasively from brachial cuff-assessment. PWV was determined regionally in the aortic arch using through-plane and in-plane velocity-encoded CMR, and locally at the proximal descending aorta using in-plane velocity-encoded CMR. Validity of the Bramwell-Hill model was tested by evaluating associations between distensibility and PWV. Also, theoretical PWV was calculated from distensibility measurements and compared with pressure-assessed PWV. In-plane velocity-encoded CMR provides stronger correlation (p = 0.02) between CMR and pressure-assessed PWV than through-plane velocity-encoded CMR (r = 0.69 versus r = 0.26), with a non-significant mean error of 0.2 ± 1.6 m/s for in-plane versus a significant (p = 0.006) error of 1.3 ± 1.7 m/s for through-plane velocity-encoded CMR. The Bramwell-Hill model shows a significantly (p = 0.01) stronger association between distensibility and PWV for local assessment (r = 0.8) than for regional assessment (r = 0.7), both for CMR and for pressure-assessed PWV. Theoretical PWV is strongly correlated (r = 0.8) with pressure-assessed PWV, with a statistically significant (p = 0.04) mean underestimation of 0.6 ± 1.1 m/s. This theoretical PWV-estimation is more accurate when invasively-assessed pulse pressure is used instead of brachial cuff-assessment (p = 0.03). CMR with in-plane velocity-encoding is the optimal approach for studying Bramwell-Hill associations between local PWV and aortic distensibility. This approach enables non-invasive estimation of local pulse pressure and distensibility.
    Journal of Cardiovascular Magnetic Resonance 01/2012; 14(1):2. DOI:10.1186/1532-429X-14-2 · 5.11 Impact Factor
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    • "In the PWV versus age plots (Figure 7) the age-related increase in the PWV was significant in the aortic arch (Figure 7a, p < 0.05) and thoracoabdominal aorta (Figure 7b, p < 0.05) with values in good agreement with those quantified previously [7,8,24,25]. The results for the thoraco-abdominal PWV (Figure 7b) agree qualitatively with previous studies [8,21], where the age-related effect in PWV was found to be reduced compared to the aortic arch. "
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    ABSTRACT: Stiffening of the arteries results in increased pulse-wave velocity (PWV), the propagation velocity of the blood. Elevated aortic PWV has been shown to correlate with aging and atherosclerotic alterations. We extended a previous non-triggered projection-based cardiovascular MR method and demonstrate its feasibility by mapping the PWV of the aortic arch, thoraco-abdominal aorta and iliofemoral arteries in a cohort of healthy adults. The proposed method "simultaneously" excites and collects a series of velocity-encoded projections at two arterial segments to estimate the wave-front velocity, which inherently probes the high-frequency component of the dynamic vessel wall modulus in response to oscillatory pressure waves. The regional PWVs were quantified in a small pilot study in healthy subjects (N = 10, age range 23 to 68 yrs) at 3T. The projection-based method successfully time-resolved regional PWVs for 8-10 cardiac cycles without gating and demonstrated the feasibility of monitoring beat-to-beat changes in PWV resulting from heart rate irregularities. For dual-slice excitation the aliasing was negligible and did not interfere with PWV quantification. The aortic arch and thoracoabdominal aorta PWV were positively correlated with age (p < 0.05), consistent with previous reports. On the other hand, the PWV of the iliofemoral arteries showed decreasing trend with age, which has been associated with the weakening of muscular arteries, a natural aging process. The PWV map of the arterial tree from ascending aorta to femoral arteries may provide additional insight into pathophysiology of vascular aging and atherosclerosis.
    Journal of Cardiovascular Magnetic Resonance 12/2011; 13(1):81. DOI:10.1186/1532-429X-13-81 · 5.11 Impact Factor
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