| Part one:Assessment of ascending aortic elasticity with dual-source CT:a feasibility study and related influencing factors analysisObjects:To evaluate the feasibility and clinical application value of ECG-gated dual-source(DS) CT in the assessment of ascending aortic elasticity and analyse the related influencing factors in normal adults.Materials and Methods:118cases of healthy subjects (87males,31females, aged26～80years with a mean of53.28±11.09) were enrolled. The lifestyle and clinical characteristics of all participants were obtained by completion of a questionnaire and checked by interview.We collected information including heart rate, systolic blood press(SBP), diastolic blood press(DBP), height, weight, smoking status, alcohol consumption and whether with abnormal lipid levels or not. All participants were subjected to coronary angiography using dual-source CT (Somatom Definition, Germany, Siemens). Raw data were reconstructed in5%steps between5and100%of the RR interval from the ECG. We obtained20phases images in each participant. The maximum and minimum volumes and cross-sectional areas of the region of interest (ROI) were measured at best-diastole and best-systole phase, respectively. We used3common parameters of aortic elastic properties:Aortic distensibility(AD,×10-3mmHg-1), Aortic compliance(AC, mm2/mmHg) and Aortic stiffness index(β). Two groups of aortic elastic parameters were calculated by the data of volumes and cross-sectional areas of the ROI. The agreement of measuring aortic elastic parameters using volumes and areas were analysed. We determined the relationship between age and aortic elastic parameters, additionally analysed relation of aortic elasticity to other clinical characteristics.Results:1. The volumes and cross-sectional areas of the ROI changed regularly during the cardiac cycle. Monitoring change throughout the cardiac cycle of all participants, it was notes the ascending aorta achieved the maximum (best-systole phase) at an RR interval of23.09±3.51%and the minimum(best-diastole phase) at an RR interval of97.03±2.55%. There are no significant correlations between the phases and the mean heart rate (r=0.143, P=0.123; r=-0.029, P=0.754). To assess interobserver and intraobserver variabilities, the volumes and cross-sectional areas were measured by two independent observers and by one observer twice at two separate times by a single experienced observer who was unaware of the clinical data. There were no significant differences and excellent correlations (r=1.0) between every two measurements. The average data of the three measurements were used(Vs, Vd, cm3;Ss, Sd, mm2).2. The average cross-sectional areas which parallel to the axis of human body were converted by maximum and minimum volume of the ROI, the parameters to elevate the ascending aortic elasticity were calculated:ADv(2.75±1.50,×10-3mmHg"1), ACv(2.04±0.85, mm2/mmHg), βv(10.77±8.06); Another group of aortic elastic parameters were calculated by the cross-sectional areas which perpendicular to the center curve of the ascending aorta vascular:ADs(2.84±1.68,×10-3mmHg-1), ACs(1.98±0.92, mm2/mmHg), βs(11.13±9.00). The parameters of aortic elastic properties measured by volumes were compared to that by cross-sectional areas. There was excellent correlation between these two methods. The correlation coefficient of the three parameters AD, AC,β were0.986,0.986,0.988, respectively.3. Age showed significantly correlation with all the parameters. There was an age-dependent decrease of ADv, ACv, ADs, ACs and the increase of βv, Ps. Curve estimation showed the best fit model was Compound model for age and ADv, ACv, ADs, ACs and Cubic model for age and βv, βs. In order to further evaluate the relationship between age and elastic parameters, the participants were divided into4age groups (<45years old,45～54years old,55～64years old,>64years old) and the parameters among the age groups were compared. Statistically significant differences in elastic parameters were found among all age groups, ADv, ACv, ADs, ACs decreased while βv and βs increased with the increase of age. There were significant differences of every different elastic parameters between each pair of age groups in multiple comparisons except βv and Ps between group<45years old and45～54years old and βv between group45～54years old and55～64years old.4. There were no differences in all elastic parameters between genders. Regarding smoking, there was decreased ADv (t=2.949, P=0.004), ADs (t=3.288, P=0.002), ACv (t=2.538, P=0.012) and ACs (t=3.196, P=0.002) in current smokers compared to former or nonsmokers, all other comparisons for βv and βs showed no differences. There were no significant differences between alcohol consumption≥2times/week and alcohol consumption<2times/week for the elastic parameters. High lipid level was associated with decreased ADv (t=3.232, P=0.002), ACv (t=2.889, P=0.005), ADs (t=3.225P=0.002), ACs (t=2.843, P=0.005) and increased βv (t=-2.172, P=0.036) and βs (t=-2.098, P=0.042). In correlation analysis, the relationship between BMI and arterial elasticity showed no significant difference. SBP was negatively correlated with ADv (rs=0.531, P=0.000), ACv (rs=-0.466, P=0.000), ADs (rs=-0.523, P=0.000), ACs (rs=-0.449, P=0.000) and positively correlated with βv (rs=0.440, P=0.000) and βs (rs=0.441, P=0.000). DBP was correlated with ACv (rs=0.202, P=0.028) and had no correlation with the other elastic parameters. Heart rate was correlated with ADv (rs=-0.232, P=0.011), βv (rs=0.200, P=0.030), ADs rs=-0.232, P=0.012), ACs (rs=-0.187, P=0.043), βs (rs=0.202, P=0.027), but the correlation was not very strong (rs<0.5). In further multiple regression analysis, ADv, ADs were independently associated with age, SBP, heart rate, smoking status and high lipid levels (R2=0.740, P=0.000;R2=0.740, P=0.000). ACv was independently associated with age, SBP, DBP, high lipid levels (R2=0.778, P=0.000). ACs was independently associated with age, SBP, high lipid levels (R2=0.659, P=0.000). βv and Ps were independently associated with age and high lipid levels (R2=0.623, P=0.000; R2=0.632, P=0.000).Conclusions:1. EGG-DSCT can obtain the data of regular diastole and systole of the ascending aorta accompanied with the cardiac pulsation during cardiac cycle, so it is a feasible and novel modality to assess aortic elasticity. There is excellent correlation between parameters of aortic elastic properties measured by volumes and that by cross-sectional areas, which means both methods are feasible ones. Both measured by volumes and measured by cross-sectional areas methods have advantages and disadvantages, which suggests that it should consider both methods synthetically.2. Age is the major factor that influence and correlated significantly with aortic elasticity. Aortic elasticity decreases with age. There are different variation and sensibility among elastic parameters.3. Current smoking status and hyperlipemia are related to lower ascending aortic elasticity. Increased SBP is associated with decreased ascending aortic elasticity significantly. In addition, there is relationship between heart rate and aortic elasticity. Part two:Assessment of ascending aortic elasticity by dual-source CT in patients with essential hypertensionObjects:To investigate the elastic properties of the ascending aorta as well as factors affecting these parameters in patients with essential hypertension with ECG-gated dual-source (DS) CT.Materials and Methods:81cases of subjects with essential hypertension (50males,31females, aged32～81years with a mean of58.77±10.09) were enrolled. Subjects were deemed hypertensive if a history of hypertension was present and the BP of all participants were controlled good or poor with the regularly use of medications.The lifestyle and clinical characteristics of all participants were obtained as part one.We collected information including heart rate, systolic blood press (SBP), diastolic blood press (DBP), height, weight, smoking status, alcohol consumption and whether with abnormal lipid levels or not, including the course of disease. Forty normal subjects with normal BP were selected from part one as control group. The EH subjects were separated into two groups (38good controlled hypertensive group and43poor controlled hypertensive group) according BP controlled situation. All participants were subjected to coronary angiography using dual-source CT (Somatom Definition, Germany, Siemens). Raw data were reconstructed and measured as part one. We firstly determined relation of aortic elasticity to all clinical characteristics in order to observe which factors can influence aortic elastic parameters. And then analysed the difference between EH subjects and normotensive controlled subjects and the characteristic of aortic elasticity in EH subjects.Results:1. In EH subjects, there were no differences in all elastic parameters between genders, current smokers and former or nonsmokers, alcohol consumption≥2times/week and alcohol consumption<2times/week. Regarding lipid levels, there was decreased ADv (t=2.550, P=0.013), ACv (t=2.304, P=0.024), ADs (t=2.291, P=0.025), ACs (t=2.113, P=0.038) in high lipid levels compared to normal lipid levels, all other comparisons for βv and βs showed no differences. In correlation analysis, age showed significantly correlation with all the parameters in all EH subjects. There was an age-dependent decrease of ADv (rs=-0.763, P=0.000), ACv (rs=-0.750, P=0.000), ADs (r,=-0.821, P=0.000), ACs (rs=-0.826, P=0.000) and the increase of βv (rs=0.773, P=0.000), βs (rs=0.832, P=0.000). The relationship between BMI and arterial elasticity showed no significant difference. SBP was negatively correlated with ADv (rs=-0.411, P=0.000), ACv (rs=-0.479, P=0.000), ADs (rs=-0.329, P=0.003), ACs (r,=-0.397, P=0.000) and positively correlated with βv (rs=0.308, P=0.005) and βs (rs=0.224, P=0.044). On the other hand, DBP was positively correlated with ADv (rs=0.295, P=0.000), ACv (rs=0.269, P=0.000), ADs (rs=0.321, P=0.001), ACs (rs=0.328, P=0.001) and had negative correlation with βv (rs=-0.375, P=0.000) and ps (rs=-0.403, P=0.000). Heart rate showed no relation to arterial elasticity. The course of disease was correlated with ADv (rs=-0.254, P=0.022), pv (rs=0.266, P=0.016), ADs (rs=-0.304, P=0.006), ACs (rs=-0.233, P=0.036), βs (r,=0.323, P=0.003), but the correlation was not very strong (rs<0.5). In further multiple regression analysis, ADv was independently associated with age, SBP and high lipid levels (R2=0.590, P=0.000). ACv was independently associated with age, SBP, DBP and high lipid levels (R2=0.722, P=0.000). βv was independently associated with age (R2=0.501, P=0.000). ADs was independently associated with age, SBP and high lipid levels (R2=0.678, P=0.000). ACs was independently associated with age, SBP, DBP and high lipid levels (R2=0.812, P=0.000). Ps was independently associated with age and the course of disease (R2=0.531,P=0.000).2. There was no difference between EH group and normotensive control group in respect to baseline clinical characteristics except BMI, SBP and DBP. All the aortic elastic parameters were found to be significantly different between the two groups. ADv, ACv, ADs, ACs were significantly lower in EH group when compared to control group while βv, Ps were higher, which means the aortic elasticity of EH patients were lower than that of normotensive participants.3. EH subjects were separated into good controlled hypertensive group and poor controlled hypertensive group based on whether BP was controlled under140/90. There was significant difference between groups in respect to SBP. The DBP of poor controlled hypertensive group was significantly higher than good controlled hypertensive group and control group. There were statistically significant differences among groups in respect to all elastic parameters.In the comparison of every two groups, all the parameters were found to be significantly different when poor controlled hypertensive group compared with normotensive control group. There were significant differences in ACv, ADs, ACs when good controlled hypertensive group compared to the control group. Among good controlled hypertensive group and poor controlled hypertensive group, the elastic parameters ADv, ACv were different. Conclusions:1. Aortic elasticity in subjects with EH decreases along with age growth. SBP is negatively correlated with aortic elasticity and DBP is positively correlated with it. These findings suggest that the control of BP in clinic should focus on the lower of SBP and make sure DBP can not be too low. The arterial stiffness in EH patients increases with the course of disease. Hyperlipemia is related to lower aortic elasticity in EH patients, which means we should realize the important of effective reduction of lipid levels.2. The aortic elasticity of EH patients is significantly lower than normotensive subjects and this difference between two groups may put the reduction of aortic elasticity as a cause of hypertension. In this way, aortic elasticity has become one of the predictors for patients at high risk of hypertension. Moreover, the differences of the state of hypertensive patients which were controlled by drug therapy influence the elasticity of ascending aorta, which indicate monitoring the change of aortic elasticity would help improve clinical medication. It should consider and synthesize different parameters of elasticity because they have different sensibility.3. ECG-gated DSCT can provide valuable assessment of aortic elasticity in patients with essential hypertension, which means it can not only show the structural changes of cardiovascular diseases and the function of left ventricular, but also further provide useful functional information of the aorta, forming the real one-stop multi-function inspection and becoming a promising modality. |
PDF Full Text Request