Deep inside the abdomen, the body’s largest blood vessel quietly widens and stiffens with age, and in some people it swells into a dangerous bulge that can rupture without warning. Now, one of the largest population-based investigations of its kind has mapped how the elastic properties of the thoracic aorta, measured with cardiovascular magnetic resonance imaging, relate to the size and blood flow of the infrarenal aorta, the very segment where most fatal aneurysms form. The study, conducted within the Hamburg City Health Study and published in Clinical Research in Cardiology, offers both encouraging signals and sobering cautions for the future of aneurysm screening.
The research team, led by Katharina Alina Riedl of the University Medical Center Hamburg-Eppendorf and collaborators at institutions including Charité Berlin and the German Centre of Cardiovascular Research, analyzed data from 2,093 participants who had undergone both advanced magnetic resonance imaging of the heart and aorta and a dedicated ultrasound examination of the abdominal aorta. The participants, drawn from the first 10,000 volunteers enrolled in the Hamburg City Health Study between February 2016 and November 2018, had a median age of 66 years, and roughly 42 percent were women. The Hamburg City Health Study is an ambitious, single-center, prospective epidemiological project aiming to follow more than 20,000 residents of Hamburg aged 45 to 74 over the long term, making it an ideal laboratory for studying how vascular aging manifests in a general population rather than in selected patient groups.
At the heart of the study are two measurements that cardiologists describe as windows into the biological age of the arteries. The first is pulse wave velocity, or PWV, which quantifies how fast the pressure wave generated by each heartbeat travels along the aortic wall. A stiffer artery propagates the wave more quickly, so higher PWV signals greater arterial stiffness, itself both a contributor to and a consequence of atherosclerosis and vascular aging. The second is aortic distensibility, or AD, which captures how much the aortic wall expands with each pulse of blood; a healthy, elastic aorta distends readily, whereas a stiffened vessel barely moves. Both parameters were derived from two-dimensional phase-contrast velocity-encoded CMR sequences acquired on a 3 Tesla scanner, with regions of interest placed manually in the ascending and descending aorta and then automatically propagated through the cardiac cycle.
The technical approach matters, because measuring aortic stiffness is notoriously method-sensitive. The team computed PWV as the distance between two measurement points divided by the transit time of the pulse wave, with the distance determined precisely by tracing an aortic centerline on a parasagittal T2-weighted HASTE image rather than estimating it from surface landmarks. The transit time was determined using the PWV 50 percent algorithm, which identifies the moment flow reaches half of its peak in each aortic segment, a method chosen because prior work showed it delivers the highest reproducibility with the fewest outliers. Distensibility, in turn, was calculated as the relative change in aortic diameter over the cardiac cycle divided by the pulse pressure measured at the brachial artery. This centerline-based CMR approach stands in contrast to the conventional carotid-femoral PWV technique, which relies on approximate surface distances and, the authors argue, may be unreliable in people with enlarged abdominal aortas because it samples a different vascular territory.
The ultrasound side of the investigation focused on the infrarenal aorta, the segment below the renal arteries where the overwhelming majority of abdominal aortic aneurysms arise. Using a convex array transducer, sonographers measured the maximum anteroposterior diameter in systole with the outer-to-outer method, as well as the peak flow velocity of blood moving through the vessel. Following current European clinical practice guidelines, a diameter between 25 and 29 millimeters was classified as ectasia and a diameter of 30 millimeters or more as an aneurysm. The median diameter in the cohort was 18.1 millimeters and the median peak flow velocity was 98.6 centimeters per second. In total, 55 participants had either ectasia or an aneurysm, including 21 with a true aneurysm, a prevalence consistent with earlier reports from the same cohort.
The statistical analysis, performed with linear and logistic regression models adjusted progressively for age, sex, and classical cardiovascular risk factors including hypertension, hyperlipidemia, diabetes, smoking, and body mass index, produced a nuanced picture. After adjustment for age and sex, the maximum infrarenal aortic diameter was significantly associated with the distensibility of the descending thoracic aorta, with a regression coefficient of −0.572 and a p-value of 0.009, meaning that people whose descending aorta distends less also tend to have wider infrarenal segments. Likewise, peak flow velocity in the infrarenal aorta was significantly associated with pulse wave velocity, with a coefficient of −0.399 and a p-value of 0.029, indicating that faster aortic pulse waves travel alongside slower peak flow in the abdominal vessel. Adding these stiffness parameters to models containing only age and sex significantly improved model fit in both cases, as confirmed by likelihood ratio tests.
Perhaps the most striking findings emerged when the researchers compared participants with ectasia or aneurysm against those with normal aortic diameters. The 55 affected individuals had significantly higher median pulse wave velocity, 8.59 versus 7.58 meters per second, alongside significantly lower distensibility in both the ascending and descending aorta and significantly lower peak flow velocity, 84.30 versus 98.70 centimeters per second. They also carried a heavier burden of cardiovascular risk factors, with significantly higher rates of hypertension, hyperlipidemia, smoking, prior myocardial infarction, and elevated body mass index. Yet when the same stiffness parameters were tested as predictors of prevalent ectasia or aneurysm in adjusted logistic regression models, none retained a statistically significant predictive value. The differences were real but modest in absolute terms, and the small number of affected participants, particularly the few women in this subgroup, limited statistical power.
This apparent paradox, significant group differences but no individual-level predictive power, carries an important message for the field. The authors conclude that CMR-based aortic stiffness parameters are associated with infrarenal aortic geometry and flow, but that their diagnostic, screening, and prognostic value remains to be established. Screening for abdominal aortic aneurysm currently rests on simple ultrasound diameter thresholds, and the new data suggest that thoracic stiffness measurements are unlikely to replace that approach. However, the findings leave open the possibility that pulse wave velocity and distensibility could help identify individuals at risk of future aneurysm development or rupture vulnerability, questions that the ongoing follow-up of the Hamburg cohort is designed to address. The biology reinforces this caution: the infrarenal aorta has a lower elastin-to-collagen ratio than the thoracic aorta, so stiffness in one segment does not simply mirror stiffness in the other.
The study is not without limitations, which the authors acknowledge candidly. It was conducted at a single center, the cohort contained far more men than women, and only 21 participants had a true aneurysm, an expected figure given the population-based design and the known prevalence of roughly 0.8 percent in this cohort. Peak flow velocity may also be confounded by the cross-sectional area of the vessel, since a larger lumen mechanically reduces peak velocity regardless of wall stiffness. The team used two-dimensional flow CMR rather than the more information-rich four-dimensional technique, a deliberate trade-off favoring fast acquisition and feasibility in large population studies, and brachial blood pressure served as a surrogate for central aortic pressure in the distensibility calculation. Nonetheless, by combining magnetic resonance and ultrasound data in the same large, unselected sample, the study represents the largest investigation to date linking CMR-derived aortic stiffness with ultrasound-based infrarenal parameters, and it sets the stage for longitudinal analyses that may finally determine whether the stiffness of the great vessels can foretell the vessels’ most dangerous failure mode.
Subject of Research: Associations between CMR-based aortic stiffness parameters and ultrasound-based infrarenal aortic parameters in a population-based cohort
Article Title: Associations of CMR-based pulse wave velocity and aortic distensibility with infrarenal ultrasound-based aortic parameters in the Hamburg City Health Study
Article References: Riedl, K. A., Di Carluccio, E., Lund, G., Huellebrand, M., Hennemuth, A., Braren, R., Kirchhof, P., Blankenberg, S., Tilemann, L., Ziegler, A., Behrendt, C. A., Muellerleile, K., & Kölbel, T. (2026). Associations of CMR-based pulse wave velocity and aortic distensibility with infrarenal ultrasound-based aortic parameters in the Hamburg City Health Study. Clinical Research in Cardiology. https://doi.org/10.1007/s00392-026-03029-8
Image Credits: AI Generated
DOI: 10.1007/s00392-026-03029-8
Keywords: pulse wave velocity, aortic distensibility, aortic stiffness, abdominal aortic aneurysm, cardiovascular magnetic resonance, infrarenal aorta, ultrasound, Hamburg City Health Study, arterial stiffening, vascular aging, aneurysm screening, cardiovascular risk factors
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Phoebe Ingram. (September 23, 2026). MRI Reveals Aortic Stiffness Links to Aneurysm Risk in Large Population Study. Scienmag. https://scienmag.com/mri-reveals-aortic-stiffness-links-to-aneurysm-risk-in-large-population-study/
Phoebe Ingram. “MRI Reveals Aortic Stiffness Links to Aneurysm Risk in Large Population Study.” Scienmag, 23 September 2026, https://scienmag.com/mri-reveals-aortic-stiffness-links-to-aneurysm-risk-in-large-population-study/. Accessed 23 September 2026.
Phoebe Ingram. “MRI Reveals Aortic Stiffness Links to Aneurysm Risk in Large Population Study.” Scienmag. September 23, 2026. https://scienmag.com/mri-reveals-aortic-stiffness-links-to-aneurysm-risk-in-large-population-study/
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Tags: abdominal aorta aneurysm screeningabdominal aortic aneurysmadvanced imaging for aneurysm risk assessmentage-related aortic stiffeninganeurysm screeningaortic distensibilityaortic stiffnessaortic stiffness and aneurysm riskarterial stiffeningcardiovascular magnetic resonancecardiovascular magnetic resonance imaging in vascular healthcardiovascular risk factorsHamburg City Health StudyHamburg City Health Study vascular findingsimpact of aortic elasticity on aneurysm formationinfrarenal aortainfrarenal aorta size and blood flowlarge population aortic aneurysm studyMRI aortic elasticity measurementpopulation-based cardiovascular researchpulse wave velocitythoracic aorta MRI analysisultrasoundvascular aging
