document: aortic aneurysm ( aa ) can be life - threatening and aorta size is the best criterion for determining if an intervention is necessary to prevent ruptures , dissections or aneurysm - related deaths.1 ) however , even large aas seldom cause symptoms,2)3 ) although the incidence of aortic disease increases with age.4)5 ) therefore , it is important for clinicians to be cautious in their evaluation of patients at risk . 
   aneurysm of the ascending thoracic aorta ( ata ) most often results from cystic medial degeneration.2 ) atherosclerosis is an infrequent cause of aneurysm of ata , in contrast to that of the descending thoracic aorta ( dta ) and abdominal aorta , where atherosclerosis plays an important role in development of aa.2 ) meanwhile , thoracic aas ( taas ) and abdominal aas ( aaas ) share common risk factors , such as age and hypertension 
   . therefore , elderly male subjects with hypertension might be at high risk for both taa and aaa . 
   efforts to detect high risk populations for coronary heart disease ( chd ) have been widely applied and coronary calcium measurement using non - contrast computed tomography ( ct ) is the method of choice for assessing cardiovascular risk in asymptomatic subjects.6 ) screening for aaa using ultrasound has been recommended in elderly men who are current or past smokers,7 ) but the screening strategy for taa in elderly subjects is not well - established , even though it is a fatal disease.8)9 ) the more widespread applications of cardiac ct and thoracic ct for cardiovascular risk stratification and lung cancer screening have made it possible to measure thoracic aortic diameter using non - contrast ct , resulting in several successful case reports.10)11 ) the purpose of the current study was to use non - contrast ct in a prospective manner to explore the prevalence of aas and determine whether screening for chd and aas is necessary in a population with multiple risk factors for chd in a korean population . 
   five hundreds and two consecutive korean male hypertensive patients without history of aa were prospectively enrolled from june , 2012 to april , 2013 at the outpatient clinic of severance cardiovascular hospital ( seoul , korea ) . 
   subjects were eligible if they were 65 years old and had provided signed informed consent . of these 542 patients who had done non - contrast ct of whole aorta , 15 patients ( 2.8% ) with a history of aortic valve surgery and 30 patients ( 5.5% ) with a suboptimal ct image were excluded . 
   most of the suboptimal images were those with errors in raw ct data storage , which caused problems of analysis in the sagittal and coronal planes using reconstructed images . 
   serum calcium , phosphorus , total cholesterol , low density lipoprotein - cholesterol ( ldl - c ) , high density lipoprotein - cholesterol ( hdl - c ) , triglycerides and serum creatinine levels were measured after a minimum 12-hour fasting period . 
   hypertension was defined as systolic blood pressure 140 mm hg and/or diastolic blood pressure as 90 mm hg or treatment with antihypertensive agents . 
   diabetes was defined as treatment with hypoglycemic agents or insulin , or fasting glucose 126 mg / dl . 
   dyslipidemia was defined as any of the following : total cholesterol 240 mg / dl , ldl - c 130 mg / dl , hdl - c 40 mg / dl , triglyceride 150 mg / dl or treatment with lipid lowering agents . 
   all examinations were performed using an aquilion one 320-row ct system ( toshiba medical systems , otawara , japan ) . 
   dual scanograms were used for planning the examination and determining the anatomical range to be covered . 
   multiple volumes were placed to cover the entire aorta from above the aortic arch to the aortic bifurcation . 
   patients underwent aorta ct with a prospective electrocardiography - gating wide - volume protocol ( from four to six volumes , according to body height ) . 
   the tube voltage was 120 kv and the effective tube current was adjusted using the adaptive iterative dose reduction three dimensional algorithm . 
   the resulting four to six individual volume data sets were automatically stitched together immediately after reconstruction to generate one ct data set of the whole aorta . 
   all data were reconstructed using a standard soft - tissue and lung kernel ( fc43 ) . 
   maximal ascending aorta diameter ( atamax ) was measured in the axial plane from just above the aortic root to the aortic arch perpendicular to the aortic axis . 
   similarly , maximal descending thoracic aorta diameter ( dtamax ) was measured at the dta distal from the aortic arch to the diaphragm level in the same axis ( fig . 
   1 ) . atamax and dtamax were confirmed in the sagittal and coronal planes using reconstructed images ( fig . 
   maximal thoracic aorta diameter ( tamax ) was defined as the largest diameter among atamax , dtamax and maximal diameter of the aortic arch . 
   maximal abdominal aortic diameter ( aamax ) was defined as the maximal diameter of the abdominal aorta from the diaphragm to the first slice superior to the aortic bifurcation . 
   taa was defined as tamax 40 mm and aaa was defined as aamax 30 mm.7)12 ) distribution of relevant variables was reported either as a percentage or as the meanstandard deviation . 
   a binary logistic regression analysis was used to identify risk factors associated with taa and aaa . 
   variables with a p<0.2 in univariate analysis were included in the multiple logistic regression model . 
   collinearity among explanatory variables was identified using variance inflation factor ( vif ) , and highly correlated variables ( vif>5 ) were excluded . 
   five hundreds and two consecutive korean male hypertensive patients without history of aa were prospectively enrolled from june , 2012 to april , 2013 at the outpatient clinic of severance cardiovascular hospital ( seoul , korea ) . 
   subjects were eligible if they were 65 years old and had provided signed informed consent . of these 542 patients who had done non - contrast ct of whole aorta , 15 patients ( 2.8% ) with a history of aortic valve surgery and 30 patients ( 5.5% ) with a suboptimal ct image were excluded . 
   most of the suboptimal images were those with errors in raw ct data storage , which caused problems of analysis in the sagittal and coronal planes using reconstructed images . 
   height , weight , and blood pressure were measured during their visit . serum calcium , phosphorus , total cholesterol , low density lipoprotein - cholesterol ( ldl - c ) , high density lipoprotein - cholesterol ( hdl - c ) , 
   hypertension was defined as systolic blood pressure 140 mm hg and/or diastolic blood pressure as 90 mm hg or treatment with antihypertensive agents . 
   diabetes was defined as treatment with hypoglycemic agents or insulin , or fasting glucose 126 mg / dl . 
   dyslipidemia was defined as any of the following : total cholesterol 240 mg / dl , ldl - c 130 mg / dl , hdl - c 40 mg / dl , triglyceride 150 mg / dl or treatment with lipid lowering agents . 
   all examinations were performed using an aquilion one 320-row ct system ( toshiba medical systems , otawara , japan ) . 
   dual scanograms were used for planning the examination and determining the anatomical range to be covered . 
   multiple volumes were placed to cover the entire aorta from above the aortic arch to the aortic bifurcation . 
   patients underwent aorta ct with a prospective electrocardiography - gating wide - volume protocol ( from four to six volumes , according to body height ) . 
   the tube voltage was 120 kv and the effective tube current was adjusted using the adaptive iterative dose reduction three dimensional algorithm . 
   the resulting four to six individual volume data sets were automatically stitched together immediately after reconstruction to generate one ct data set of the whole aorta . 
   all data were reconstructed using a standard soft - tissue and lung kernel ( fc43 ) . 
   maximal ascending aorta diameter ( atamax ) was measured in the axial plane from just above the aortic root to the aortic arch perpendicular to the aortic axis . 
   similarly , maximal descending thoracic aorta diameter ( dtamax ) was measured at the dta distal from the aortic arch to the diaphragm level in the same axis ( fig . 
   1 ) . atamax and dtamax were confirmed in the sagittal and coronal planes using reconstructed images ( fig . 
   maximal thoracic aorta diameter ( tamax ) was defined as the largest diameter among atamax , dtamax and maximal diameter of the aortic arch . 
   maximal abdominal aortic diameter ( aamax ) was defined as the maximal diameter of the abdominal aorta from the diaphragm to the first slice superior to the aortic bifurcation . 
   taa was defined as tamax 40 mm and aaa was defined as aamax 30 mm.7)12 ) 
   distribution of relevant variables was reported either as a percentage or as the meanstandard deviation . 
   a binary logistic regression analysis was used to identify risk factors associated with taa and aaa . 
   variables with a p<0.2 in univariate analysis were included in the multiple logistic regression model . 
   collinearity among explanatory variables was identified using variance inflation factor ( vif ) , and highly correlated variables ( vif>5 ) were excluded . 
   patient demographics and clinical characteristics are shown in table 1 . the mean age was 73 years . 
   diabetes , dyslipidemia and coronary artery disease were observed in 171 patients ( 34.5% ) , 318 patients ( 64.1% ) and 256 patients ( 51.6% ) , respectively . 
   three hundred and sixty - four patients ( 73.4% ) had a history of smoking . 
   mean diameter of atamax , dtamax , tamax , and aamax was 38.44.0 mm , 28.53.0 mm , 38.94.0 , and 23.05.5 mm , respectively . 
   the prevalence of taa and aaa was 36.5% ( 181/496 ) and 6.0% ( 30/496 ) , respectively . 
   there were 16 patients ( 3.2% ) who had taa and aaa simultaneously . however , prevalence of aa suitable for an indication for intervention according to current guidelines ( tamax 55 mm and aamax 60 mm)2 ) was very low in this study . 
   those who were indicated for intervention were seen only in one case of the taa group and one case of the aaa group . 
   prevalence of taa was 64.6% in patients with aaa and 40.0% in patients without aaa . 
   patients with aaa had a higher occurrence of taa compared with those without aaa ( p=0.010 ) ( fig . 
   there was no significant difference in prevalence of taa between nonsmokers and those who had a history of smoking or were current smokers . 
   in contrast , prevalence of aaa was significantly higher in current / past smokers compared to non - smokers ( p=0.046 ) . 
   of the 365 current / past smokers , aaa was found in 27 patients ( 7.4% ) , but of the 124 non - smokers , aaa was observed in only three patients ( 2.4% ) , and there were no nonsmokers with a large aaa ( > 40 mm ) . 
   determinants for taa , aaa and both taa and aaa are shown in table 2 . in the multivariate logistic regression analysis , 
   determinants for taa were age { odds ratio ( or ) 1.059 , 95% confidence interval ( ci ) 1.018 - 1.101 , p=0.005 } , absence of dyslipidemia ( or 0.621 , 95% ci 0.418 - 0.923 , p=0.018 ) , body surface area ( or 11.92 , 95% ci 2.787 - 50.97 , p=0.001 ) , diastolic blood pressure ( or 1.029 , 95% ci 1.009 - 1.049 , p=0.004 ) and presence of aaa ( or 3.070 , 95% ci 1.398 - 6.754 , p=0.005 ) . 
   in contrast , aaa was independently associated with presence of dysplipidemia ( or 2.792 , 95% ci 1.091 - 7.143 , p=0.032 ) , current / past smokers ( or 4.074 , 95% ci 1.160 - 14.31 , p=0.028 ) and presence of taa ( or 3.367 , 95% ci 1.550 - 7.313 , p=0.002 ) . 
   aortic size is critical to key decisions regarding management of aas.12 ) this study evaluated the entire aorta diameter , from the thoracic aorta to the abdomen aorta just above the iliac bifurcation , using axial images of non - contrast ct scans in a population with multiple risk factors for both chd and aa . 
   the study population included high - risk individuals , but blood pressure and serum lipids were well controlled in most patients , as indicated by blood pressure and laboratory test results . nevertheless , prevalence of taa was considerably high and taa was associated with various clinical factors including older age , larger bsa and higher diastolic blood pressure . 
   interestingly , taa was associated with the absence of dyslipidemia , while aaa was significantly associated with the presence of dyslipidemia . 
   one possible explanation might be that the etiology of aas differs between ascending and descending aorta.1 ) that is , above the ligamentumarteriosum the disease is non - atherosclerotic , while below the ligamentumarteriosum arteriosclerosis is abundant.1 ) therefore , taa might not be associated with dyslipidemia . 
   another explanation for the conflicting results might be that the mean values of total cholesterol , ldl - c and hdl - c were almost within normal limits , suggesting the serum lipids were well controlled in most patients . 
   in addition , since the current study was performed at a tertiary referral hospital , many of the patients were taking statins for the primary or secondary prevention for coronary artery disease , not for the treatment of dyslipidemia . 
   therefore , effects of high lipids on atherosclerosis might be minimized in the studied population and result in conflicting outcomes . 
   therefore , further studies are needed to clarify the relationship among taa , aaa , dyslipidemia , serum cholesterol and statin therapy . 
   thoracic aortic aneurysm was more prevalent in patients with aaa compared to those without aaa , even after adjusting for multiple confounding factors . 
   in addition , more than one - third of the study subjects had a taa , and it was remarkably more prevalent than aaa among high - risk subjects in the current study , in contrast to previous reports that aaa is more prevalent than taa.1 ) taa prevalence continuously increases,13 ) and is thought to be related to increased age and hypertension in the general population . 
   however , most taas had a diameter < 50 mm , which is not large enough to indicate a need for immediate intervention . therefore , the clinical implications of the high prevalence of taa need further evaluation , since taas are known to be an indolent process and to grow very slowly , at approximately 0.1 cm per year.9)14 ) future studies should establish a method for aortic screening for taa and strategies for conservative as well as surgical management in elderly hypertensive patients . 
   previous studies consistently demonstrated a relationship between smoking and aaa.11 ) the present study , which involved a high - risk population of asian males , found that aaa was independently associated with smoking history in addition to dyslipidemia . 
   moreover , prevalence of aaa was 2.4% among nonsmokers , which is very low compared to previous studies involving caucasians.15)16 ) in addition , none of the nonsmokers had a large aaa ( > 40 mm ) . in population - based screening studies in japan , 
   aaa was rarely encountered17)18 ) and the prevalence of aaa was also reportedly low in chinese populations , even in patients with severe coronary artery disease.19 ) this suggests that race influences aaa prevalence and that asians generally have a low prevalence of aaa . 
   the present study also reported a low prevalence of aaa in an asian population and reinforced the impact of smoking on aaa . 
   these results high - light the need to clearly define the usefulness of routine screening for aaa among asian non - smokers . 
   the primary limitation of this study is that a ct scan with axial images could not properly evaluate the very proximal portion of the ascending aorta including the aortic root . 
   in addition , even in the sagittal and coronal planes , aortic root diameter could not be accurately measured using non - contrast ct due to the complexity of the structures surrounding the aortic root . therefore , different imaging modalities are needed to accurately detect aortic root aneurysms . 
   this study was performed in a population of elderly asian males with hypertension at high risk for cardiovascular disease . 
   therefore , the results of the current study can not be applied to females , other ethnicities , or groups with a low - risk of cardiovascular disease . 
   the prevalence of aa was significant and taa was more prevalent than aaa in elderly korean males with hypertension who had multiple risk factors for chd and aa . 
   future research should establish distinct screening strategies for taa and aaa according to risk factors and ethnicity . 
   the primary limitation of this study is that a ct scan with axial images could not properly evaluate the very proximal portion of the ascending aorta including the aortic root . 
   in addition , even in the sagittal and coronal planes , aortic root diameter could not be accurately measured using non - contrast ct due to the complexity of the structures surrounding the aortic root . 
   this study was performed in a population of elderly asian males with hypertension at high risk for cardiovascular disease . 
   therefore , the results of the current study can not be applied to females , other ethnicities , or groups with a low - risk of cardiovascular disease . 
   the prevalence of aa was significant and taa was more prevalent than aaa in elderly korean males with hypertension who had multiple risk factors for chd and aa . 
   future research should establish distinct screening strategies for taa and aaa according to risk factors and ethnicity .
summary: background and objectivesscreening strategies for aortic aneurysm ( aa ) according to risk factors and ethnicity are controversial . 
   this study explored the prevalence of aa and determined whether screening is necessary in a population of multiple risk factors.subjects and methodsfrom june , 2012 to april , 2013 , 542 consecutive elderly ( 65 years ) male hypertensive patients without a history of aa were prospectively enrolled . after excluding 15 patients ( 2.8% ) with aortic valve surgery , 30 patients ( 5.5% ) with suboptimal computed tomography ( ct ) images , the remaining 496 patients ( age 735 years ) comprised the study population . 
   maximal diameters of the thoracic and abdominal aorta were measured using non - contrast ct.resultsthe prevalence of thoracic aa ( taa , diameter 40 mm ) and abdominal aa ( aaa , diameter 30 mm ) was 36.5% ( 181/496 ) and 6.0% ( 30/496 ) , respectively . in the multivariate logistic regression analysis , 
   determinants for taa were age { odds ratio ( or ) 1.059 , 95% confidence interval ( ci ) 1.018 - 1.101 , p=0.005 } , dyslipidemia ( or 0.621 , 95% ci 0.418 - 0.923 , p=0.018 ) , body surface area ( or 11.92 , 95% ci 2.787 - 50.97 , p=0.001 ) , diastolic blood pressure ( or 1.029 , 95% ci 1.009 - 1.049 , p=0.004 ) and aaa ( or 3.070 , 95% ci 1.398 - 6.754 , p=0.005 ) . 
   in contrast , aaa was independently associated with dysplipidemia ( or 2.792 , 95% ci 1.091 - 7.143 , p=0.032 ) , current / past smokerfs ( or 4.074 , 95% ci 1.160 - 14.31 , p=0.028 ) , and taa ( or 3.367 , 95% ci 1.550 - 7.313 , p=0.002).conclusionthe prevalence of aa was significant and taa was more prevalent than aaa in elderly korean males with hypertension . 
   future research should establish distinct screening strategies for taa and aaa according to risk factors and ethnicity .