Body-surface adjusted aortic reference diameters for improved identification of patients with thoracic aortic aneurysms: Results from the population-based Heinz Nixdorf Recall study

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Abstract

Background

Early identification of patients at risk for thoracic aortic aneurysm (TAA) has the potential of improving prognosis. So far, however, “normal” aortic dimensions are not well defined, rendering identification of patients with enlarged aortas difficult. In the present study we aimed to (1) establish age- and gender-specific distribution of thoracic aortic diameters and (2) to determine the prevalence of asymptomatic TAA in a population-based European cohort.

Methods

Diameters of ascending thoracic aorta (ATA) and descending thoracic aorta (DTA) were measured from electron beam computed tomography (EBCT) scans of 4129 participants aged 45 to 75 years from the Heinz Nixdorf Recall study. Age- and gender-specific percentiles were calculated for body-surface adjusted aortic diameters. Multivariable linear regression was used to evaluate the association between aortic diameters and cardiovascular risk factors including age, gender and body-surface area (BSA).

Results

Aortic diameters were generally greater in the ATA than in the DTA, and were greater in men than in women (ATA: 3.71 ± 0.4 cm vs. 3.45 ± 0.4 cm, p < 0.0001; DTA: 2.82 ± 0.3 cm vs. 2.54 ± 0.3 cm, p < 0.0001). Age, male gender, blood pressure and body-surface area were independently associated with aortic diameters in both ATA and DTA. Based on our measurements age- and gender-specific percentiles for indexed ATA and DTA diameters were computed. Aneurysms  5 cm were found in 12 (0.34%) out of the total of 4129 subjects.

Conclusion

Since BSA was independently associated with increasing aortic diameters, correction of aortic diameters for BSA may be more helpful in order to reliably identify patients at risk for aneurysm formation. Based on the normal distribution of body-surface adjusted thoracic aortic diameters displayed in age- and gender-specific percentiles we suggest a cut-off point for aneurismal aortic diameter at the 95th percentile.

Introduction

Thoracic aortic aneurysm (TAA) is a serious condition, with the potential for severe complications such as aortic valve regurgitation and aortic rupture or dissection, frequently necessitating urgent open surgical or endovascular repair [1], [2], [3], [4]. Generally, TAA is considered to be rare, but data on its prevalence are limited, both by sample size and study population [5], [6], [7]. So far, only a single population-based study from Japan reported the prevalence of asymptomatic TAA with 0.16% (11 out of 6971 participants) [8]. Most recent data originate from Swedish national healthcare registers and have estimated the yearly incidence of TAA (> 5 cm) including also aortic dissection to be 16.3 per 100,000 in men and 9.1 per 100,000 in women, respectively [9].

The prerequisite for estimating the prevalence of TAA is to determine specific cut-off values. The “normal” aortic dimensions are, however, still not well defined, although several studies have tried to establish reference values using transesophageal echocardiography, magnetic resonance imaging (MRI) or computed tomography (CT) [10], [11], [12], but are limited with respect to sample size and composition of analyzed patient cohorts. In clinical practice, an aortic diameter exceeding 5 cm is usually considered an aneurysm requiring surgery. It would, however, be desirable to define aneurysm patients not only on a surgical retrospectively defined threshold [1], [17].

It was the aim of the present study to (1) to establish age- and gender-specific percentile distribution of thoracic aortic diameters using the population-based cohort of the Heinz Nixdorf Recall study in Germany and (2) to calculate the prevalence of asymptomatic TAA.

Section snippets

Study population

The Heinz Nixdorf Recall study (Risk factors, Evaluation of Coronary Calcium and Lifestyle) is the first study in Europe, which assessed cardiovascular risk factors and the prevalence of signs of subclinical coronary atherosclerosis in an unselected cohort representing the population of the Ruhr area with 6 million residents. Random samples of the general population were drawn from residents’ registration offices of the German cities of Bochum, Essen, and Mülheim/Ruhr including men and women

Baseline characteristics

Of 4814 participants of the HNR study, 4609 (95.7%) ultimately had an EBCT scan performed between December 2000 and August 2003. The remaining were either unable to receive an EBCT (obesity, claustrophobia, etc.) or disclaimed the examination. Of the 4609 subjects with an EBCT scan, 4301 (93.3%) subjects had no history of known CAD. Overall, ATA and DTA diameters were measured in 4129 (96%) of these 4301 individuals. Table 1a, Table 1b show the demographics of the study population. The mean age

Discussion

This study is the first to provide population-based reference values for thoracic aortic dimensions as assessed by non-contrast enhanced CT in a large unselected cohort free of known CAD. Percentile curves of ATA and DTA diameters computed from our results which can be accessed online may help identifying individual patients at risk for TAA.

Conclusion

In the present study, we provide reference values for thoracic aortic dimensions derived from non-contrast CT in an unselected population-based cohort. Age, gender, blood pressure and especially body-surface area were the major determinants of thoracic aortic diameters. Based on the normal distribution of body-surface adjusted thoracic aortic diameters displayed in age- and gender-specific percentiles we suggest a cut-off point for aneurismal aortic diameter at the 95th percentile.

For

Disclosures

None of the authors have declared a conflict of interest or financial disclosures.

Acknowledgments

The authors thank the participants of the Heinz Nixdorf Recall study and the entire community of Heinz Nixdorf Recall investigators and staff for their support and valuable contributions. The authors of this manuscript have certified that they comply with the Principles of Ethical Publishing in the International Journal of Cardiology.

References (35)

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    However, when studying aortic dilation and the associated risk of dissection, it is advised to take the size of the individual into account, and some reports also suggest that ascending aorta dilation should be described as aortic diameter normalized by BSA >21 mm/m2.16,19 Indeed, when normalizing aortic dimensions by BSA, women had greater ascending aortic diameters than men, which is in line with previous studies.19-21 Greater normalized aortic dimensions may associate with a poorer prognosis and further stresses the importance to correct aneurysm size to body size when assessing surveillance and potentially timing of intervention of patients with ascending thoracic aortic aneurysm.

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1

On behalf of the Investigator Group of the Heinz Nixdorf Recall Study.

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