Assessment Of Ascending Aortic Elasticity Feature In Prehypertension And Essential Hypertension,Associated Risk Factors And Association With Target Organ Damage

Background: The importance of the ascending aortic elasticity in the buffering function of systolic load and therefore in preserving tissue blooding is paramount, and the ascending aortic elasticity could be well obtained by using ECG-gated coronary CT without additional iodine contrast agent and radiation exposure. Aortic elasticity decreases correlate with high blood pressure, however, the ascending aortic elasticity feature in prehypertension and essential hypertension, its associated risk factors and association with target organ damage remain unclear.Objective: To assess parameters of the ascending aortic elasticity changes in the ECG-gated coronary CT angiography in prehypertensive and essential hypertensive subjects and demonstrate the elasticity feature and the risk factors in Part I, and further to investigate the relationship between ascending aortic elasticity with target organ damage in Part II.Materials and methods: 398 participants including 121 prehypertensive and 192 essential hypertensive patients and 85 healthy controls undergone ECG-gated coronary CT, were enrolled in our study, including 189 women and 209 men(mean age, 53.1±11.7 years). Their demographic and clinical data were collected within one week before CT examination. All participants were examined with a 128-slice dual-source CT system(Somatom Definition Flash, Siemens Healthcare, Forchheim, Germany). Images were reconstructed in 5% steps between 5 and 100% of the RR interval, 20 phases images in each participant were obtained. The maximum and minimum average diameters and cross-sectional areas of the region of interest(25 mm above the level of the beginning of left coronary artery) in 20 phases were determined. We used 3 common parameters of aortic elastic properties: Aortic distensibility(AD), Aortic compliance(AC) and Aortic stiffness index(ASI).Results:Part I1. Difference of diameter and cross-sectional area and elasticity of the ascending aorta among prehypertensive, essential hypertensive subjects and controlsThere were significant differences among three groups in respect to the standard minimum diameter(F=3.53, P<0.05) and cross-sectional area(F=9.10, P<0.001). In the comparison of every two groups, the standard minimum diameter and cross-sectional area were similar between prehypertension and controls groups. The standard minimum cross-sectional areas was significantly greater in essential hypertension than prehypertension group(P<0.01), but the minimum diameter is not. There were very significant differences among three groups in respect to AD(F=47.46, P<0.001), AC(F=34.51, P<0.001) and ASI(F=10.05, P<0.001). In the comparison of every two groups, AD and AC differ significantly within every two groups(P<0.001), however, ASI was similar between prehypertension and controls groups. The ASI was significantly greater in essential hypertension than prehypertension group(P<0.01). The ba PWV was greater in essential hypertension than prehypertension group(P<0.05). We found that age and presence of prehypertension or essential hypertension were significant predictors of the decreased AD value.2. Association between age and ascending aortic elasticity in prehypertensive, essential hypertensive subjects and controlsThere were significant correlation between age and elasticity parameters(AD, AC and ASI) in all participants [ r=-0.617,-0.539 and 0.643(P<0.001)]. In the groups of control, prehypertension, essential hypertension, the correlation coefficient of AD, ASI with age was decreased gradually. Curve estimation showed the best fitting model was Compound model for age and all elasticity parameters(AD, AC and ASI) in three groups, except for AD parameter in essential hypertension group(cubic model).3. Factors associated with ascending aortic elasticity in prehypertensive, essential hypertensive subjects and controlsThe multiple regression analysis showed AD parameter were independently associated with age and smoking status in controls, age and systolic blood pressure in prehypertensive group, age and 24-hour diastolic blood pressure and pulse pressure in essential hypertensive group separately.4. The ba PWV and ascending aortic elasticity in different groups of duration of hypertensionThe essential hypertensive participants were divided into three duration of hypertension groups, including <5y, 5~10y and >10y. There was no difference among three groups in respect to the ba PWV. There were significant differences among three groups in respect to AD(P<0.001), AC(P<0.001) and ASI(P<0.05). In the comparison of every two groups, AC value was similar between <5y and 5~10y groups, ASI was similar between 5~10y and >10y groups, in addition, AD, AC and ASI differ significantly within every two groups(P<0.05).Part II1. Comparison of ba PWV, diameter and cross-sectional area and elasticity of the ascending aorta among different numbers of TODAD(F=40.74, P<0.001), AC(F=27.0, P<0.001) decreased and ASI(F=28.0, P<0.001), the standard minimum diameter(F=2.89, P<0.05), cross-sectional areas(F=4.95, p<0.01), ba PWV(F=5.24, P<0.01) increased significantly in parallel with increasing severity of TOD, i.e. the number of organs involved(0, 1, 2, 3,P < 0.01 for trend). In the comparison of every two groups, AD, AC and ASI differ significantly between patients with the presence of TOD and patients without(P<0.01). AD and AC differ significantly between patients with the presence of TOD 1 and patients with the presence of TOD 2(P<0.01), but the ASI is not. ASI differ significantly between patients with the presence of TOD 2 and patients with the presence of TOD 3(P<0.01), but the AD and AC are not. There were not differences with respect to the standard minimum diameter and cross-sectional area in every two groups(i.e. TOD 0 and TOD 1, TOD 1 and TOD 2, TOD 2 and TOD 3). The ba PWV differ significantly between patients with TOD and patients with the presence of TOD 1(P<0.01), but not in every two groups(i.e. TOD 1and TOD 2, TOD 2 and TOD 3).2. Factors associated with TOD in hypertensive subjectsWe used logistic regression analysis to assess the independent contribution of several variables, including ba PWV, AD, AC and ASI respectively, to the presence of TOD, revealed AD, AC and ASI parameters were independently associated with presence of TOD respectively. Next, we used logistic regression analysis to assess the independent contribution of age, ba PWV, AD, AC and ASI, revealed only AD parameters were independently associated with presence of TOD.3. Clinical characteristics of subjects of three groups according to the tertile values of ADWe divided the participants into three groups according to the tertile values of AD. The severity of TOD also increased from lower to upper AD tertile(P<0.001). In fact, patients in the medial tertile had almost 7.2 times higher odds of showing at least one signs of TOD as compared with those in the highest tertile. Patients in the lowest tertile had almost 9.8 times higher odds of showing at least one signs of TOD as compared with those in the medial tertile. And patients in the medial tertile had almost 4.2 times higher odds of showing at least two signs of TOD as compared with those in the highest tertile. Patients in the lowest tertile had almost 23.33 times higher odds of showing at least two signs of TOD as compared with those in the medial tertile.Conclusions:Part I1. The ascending aortic elasticity could be well obtained by using ECG-gated coronary CT in patients with prehypertension and essential hypertension without additional iodine contrast agent and radiation exposure.2. The aortic elasticity of prehypertensive patients is significantly lower than healthy controls, however, higher than patients with essential hypertension.3. AD parameter is a more sensitive marker of ascending aortic elasticity changes than AC and ASI in patients with prehypertension and essential hypertension relatively, however, no single parameter could be determined which covers all cases and each parameter has inherent problems in measurement and interpretation. Here, three parameter inlcuding AD, AC and ASI were analyzed to achieve a more objective insight in the ascending aortic elasticity.4. Age is the main determinant factor of ascending aortic elasticity in patients with prehypertension, essential hypertension and healthy controls. The multiple regression analysis showed AD parameter was independently associated with age and smoking status in controls, age and systolic blood pressure in prehypertensive group, age and 24-hour diastolic blood pressure and pulse pressure in essential hypertensive group separately. In addition, fat and blood glucose are risk factors of reduced ascending aortic elasticity.Part II1. AD, AC and ASI parameters were independently associated with presence of TOD in hypertensive patients, namely carotid atherosclerosis, LV hypertrophy, and albuminuria, and they are more sensitive marker of hypertension related TOD than ba PWV and the ascending aortic morphology.2. AD parameter is a more sensitive marker of subclinical TOD in patients with essential hypertension than AC and ASI relatively, However, no single parameter could be determined which covers all cases and each parameter has inherent problems in measurement and interpretation. Here, three parameter inlcuding AD, AC and ASI were analyzed to achieve a more objective insight in hypertension related TOD.3. When patients were divided on the basis of tertiles, we found a higher prevalence and degree of TOD in patients in the highest tertile of AD.In conclusion, our study shows measurement of parameters of ascending aortic elasticity especially concerning AD parameter in patients with prehypertension and essential hypertension may be helpful for risk stratification and will complement screening for hypertensive subclinical TOD and even cardiovascular event.