What does unfolding of the thoracic aorta mean

A total of 32 CT scans were studied, with 10 coming from the 70 cases in the present study. Ethics approval to use the CT scans and radiographs of these patients for this research had been granted. The lateral displacement of the descending aorta was measured in the horizontal plane at the level of the root of the heart and bifurcation of the pulmonary artery.

The distance from the midline i. Since remodelling varied at the level of the root, the maximum value from several cuts was used. There was a moderate, but acceptable, association between the radiographic indices of unfolding i.

Based on these moderately good associations, the use of LD and CA to assess aortic unfolding, remodelling and tortuosity was shown to be valid. Correlations of a lateral displacement and b curvature angle measured on chest radiograph with a maximum lateral distance of the aorta measured on computed tomography CT.

Data are collected from 32 patients, with 10 from the 70 patients of the present study. To assess rotation in the chest radiographs, a vertical line was drawn on the radiograph that passed through the spinous processes in the midline. Clinical management system software tools were used. Then the left and right horizontal distances between the medial end of the clavicles and the midline were measured. The difference between these two measurements in millimetres was used as an index of chest rotation.

Large degrees of chest rotation can affect the correct measurement of intrathoracic structures such as the size of the heart and position of the aorta. The calculation of sample size was based on the primary aim to investigate the relationship between aortic unfolding and variability in ODM readings. Normality of the data was determined with the Kolmogorov—Smirnov one-sample test. Data are presented as mean sd or median range for continuous variables and absolute numbers or percentages for categorical variables.

For each patient, the mean of SV was calculated. Data collected from another 36 randomly chosen patients' radiographs were used as ICC controls. For intrarater reliability, one investigator J. The intrarater reliabilities of LD and CA were 0. For interrater reliability, two investigators J. The interrater reliabilities were 0. Linear regression analysis was used to determine the relationship between radiological measurements and the CV of SV readings as probe depth varied.

CV of SV readings. Chi-square or Fisher's exact test was used to compare categorical data. Stepwise multiple linear regression analysis was used to determine the associations between age, height, weight, known hypertension and radiological aortic measurements CA or LD. The number of probe insertion depths was inadequate i. They were excluded from further analysis. The mean age was 64 years range 32—88 , with 41 males and 29 females. All 70 PA chest radiographs had the carina situated to the left of the right pedicles.

There were no cases of scoliosis. The median difference i. A mm increase in LD was associated with a 6. Variability in oesophageal Doppler monitor ODM readings over a cm probe depth range as aorta unfolding increased, quantified by the a lateral displacement and b curvature angle measurements from erect posteroanterior chest radiograph.

Regression lines and equations were shown. CV: coefficient of variation; SV: stroke volume. The ability of chest radiography, when using LD and CA measurements, to predict the variability of SV readings measured over a cm depth range was analysed using ROC curve analysis Fig. The optimal cut-off value is shown by the open circle on the ROC curve.

The ability to achieve consistent ODM readings was further analysed by dividing patients into two post hoc groups based on the ROC curve result: i those with clinically non-significant aortic unfolding i. The two post hoc groups were similar with respect to weight, height and gender Table 1.

Demographic and ODM data for control and unreliable group patients. Data are expressed as mean sd , median range or number percentage.

Stepwise multiple regression analysis between demographic variables i. Despite it being recommended that maintenance of a constant probe depth is needed when using ODM, 12 there is a scarcity of published data quantifying the effects and describing which patients are most at risk. Reading variation has been previously attributed to variations in the cross-sectional area of the descending aorta. However, curvature of the descending aorta due to remodelling will cause alteration in the insonation angle as probe depth varies and thus change the estimated peak velocity.

Data from the present study suggest that aortic remodelling is a cause of ODM reading variation with probe depth and repositioning. The human aorta becomes stiff and unfolded with aging, predominantly due to fatigue and the fracture of elastin lamellae and subsequent remodelling in its wall. The measurements developed by this study, CA and LD, help to quantify remodelling and are based on the tortuosity of the descending thoracic aorta, the region where ODM measurements are performed.

By comparing these measurements with lateral displacement measurements of corresponding thorax CT scans in 32 patients we were able to validate the use of CA and LD as indices of remodelling.

Correlation between these indices and the CT scan measurement showed a moderate to good association with R 2 values of 0. Excellent intra- and interrater reliability shown by ICCs indicated that these two measurements were also highly repeatable.

Rotation of the chest on the radiograph can also potentially affect the reliability of CA and LD measurements. The effect of age-related changes of the aorta on Doppler flow measurements was first reported in by Gardin and colleagues.

The current controversy regarding the accuracy of ODM in validation studies can also be explained in part by a reduced reliability caused by this aortic unfolding and remodeling. Age-related changes in aortic arch geometry: relationship with proximal aortic function and left ventricular mass and remodeling. J Am Coll Cardiol ; 58 : — Age-associated elongation of the ascending aorta in adults.

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Validation of generalized transfer function. Circulation ; 95 : — Download references. We thank Mrs Latifa Boudali for her invaluable assistance in database management. You can also search for this author in PubMed Google Scholar. Correspondence to D Craiem. Reprints and Permissions.

Craiem, D. Three-dimensional evaluation of thoracic aorta enlargement and unfolding in hypertensive men using non-contrast computed tomography. J Hum Hypertens 27, — Download citation. Received : 29 August Revised : 11 December Aortic unfolding Unfolding of the aorta Unfolding of aorta.

URL of Article. Aortic dimensions and stiffness in normal adults. Aortic unfolding determined using non-contrast cardiac computed tomography: correlations with age and coronary artery calcium score. Promoted articles advertising. Case 1 Case 1. Thoracic aortic aneurysm Thoracic aortic aneurysm. Loading more images We also analyzed the relationship between aortic unfolding measurements and CAC score using stepwise multiple linear regression.

Mean aortic unfolding was Age, body surface area, and hypertension were exclusively associated with aortic unfolding. Aortic unfolding defined by measuring aortic width was a reproducible and practical method with non-contrast cardiac CT and associated with age, body surface area, and hypertension. CAC score, a well-established surrogate marker of cardiovascular disease, is positively associated with aortic unfolding.

Further study to evaluate aortic unfolding as a potential predictor of cardiovascular risk is warranted. Arterial changes with aging include lumen enlargement, wall thickening, and a reduction in the elasticity of large arteries, a process known as arteriosclerosis [1]. Although the principal change in arterial aging is medial degeneration, structural and functional changes also occur.

The structural changes include aortic lumen enlargement and wall thickening, and these can be measured using ultrasound, invasive angiography, computed tomography CT , or magnetic resonance imaging MRI [2]. Functional changes such as arterial stiffness reflecting a reduction in elasticity can be measured using several non-invasive methods, including pulse wave velocity PWV and the augmentation index AI [3] , [4].

PWV is a powerful independent predictor of mortality in subjects with hypertension, end-stage renal failure, or diabetes, and was associated with higher cardiovascular mortality, coronary heart disease CHD events, and stroke in a community-dwelling sample of older people [5] — [7]. The carotid AI is an independent predictor of all-cause and cardiovascular mortality in patients with end-stage renal failure and an independent risk marker for premature coronary artery disease CAD [8].

Aortic unfolding is a term used to describe the radiological abnormality on chest radiographs seen as widening of the mediastinum. This change occurs with aging and generally reflects proximal aortic dilation, aortic arch widening, and decreased curvature.

Unfolding is often associated with aortic calcification which implies aortic degeneration and hypertension [2] , [12]. Changes in the aortic dimensions are associated with the aortic PWV and AI between the aorta and brachial artery [13] , [14].

Age-related changes in aortic arch geometry are related to functional aortic alterations, such as decreased aortic distensibility, augmented aortic arch PWV, and increased LV mass, in individuals without overt cardiovascular disease [15]. In the present study, we defined aortic unfolding as the width of the aorta which was measured on non-contrast electrocardiography ECG -synchronized cardiac CT, as a potential risk factor reflecting arterial aging.

Measurements based on aortic width take advantage of a scale larger than those of lumen enlargement, wall thickening, or aortic distensibility, and are not influenced by temporary changes in BP or heart rate. We evaluated aortic unfolding as a potential index of arterial aging by examining its correlation with age.

In addition, to characterize aortic unfolding as a potential marker of individual cardiovascular risk, we assessed the factors influencing aortic unfolding based on correlations with risk factors for accelerated vascular aging and CAD.

Finally, we analyzed the relationship between aortic unfolding measurements and coronary artery calcium CAC as a surrogate marker of coronary atherosclerosis burden and cardiovascular risk.

Our institutional review board Yonsei University Health System approved this study and waived informed consent for this retrospective review. We enrolled consecutive asymptomatic, self-referred patients who underwent CAC scanning for screening purposes between December and May at our institution. Thoracic aortic aneurysm, severe pulmonary disease causing atelectasis or fibrosis around aorta, or kyphosis, which could influence aortic dimension, were not found on the plain chest radiographs in the subjects.

We retrospectively reviewed the medical records of all subjects to collect clinical information, including demographic data and risk factors for coronary artery disease.

Four subjects were excluded because of incomplete clinical information and six subjects were excluded due to known clinical CAD. Therefore, subjects were analyzed in this study. The scanning direction was craniocaudal, extending from the inferior border of the aortic arch to the bottom of the heart. Using semi-automated software AW Volume Share 4; GE Healthcare, Milwaukee, WI , coronary artery calcium was identified as a high-attenuation area, with attenuation exceeding the threshold of HU, in the coronary artery.

CAC scores were calculated according to the Agatston scoring method [16]. Aortic unfolding was defined as the longest distance between the ascending and descending aortas, including the aortic lumen and aortic wall, on a selected CT slice at the level of the pulmonary artery bifurcation Fig.

Two radiologists who were blind to the clinical information measured the aortic unfolding. To assess the intra-observer variability, each reader made two measurements in random order at an interval of at least 4 weeks. The mean value of the two measurements by the two radiologists was used for the analyses. Aortic unfolding index was defined as aortic unfolding divided by body surface area BSA. Aortic unfolding white line was defined as the longest distance between the ascending and descending aorta on a transaxial slice at the level of the pulmonary artery bifurcation on a selected coronary artery CT image.

Information on the presence of categorical cardiac risk factors was collected for each subject from a chart review [12] , [17] — [19]. Blood samples for lipid, fasting glucose, and plasma creatinine were obtained on the day of the CT examination. Positive smoking status was defined as current smoking or a history of smoking. Major adverse cardiac events information was obtained from patient telephone interviews and hospital records between January and April Of the subjects, subjects ranged in age from 30 to 74 years, corresponding to the age range of the Framingham cohorts.

The year risk of cardiovascular disease CVD in this group were calculated using the equations derived from the Framingham Heart Study and Framingham Offspring Study [22]. All statistical analyses were performed using SAS ver. For graphing, we used MedCalc ver Continuous variables were compared using the t- test for two groups.