Assessment Of Left Atrial Volume And Function With Electrocardiographically Gated Dual-source CT:a Preliminary Study

Part one:Assessment of left atrial volume and function 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 left atrial volume and function and analyse the related influencing factors in normal adults.Materials and Methods:92cases of healthy subjects (61males,31females, aged21～76years with a mean of52.51±11.20) 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 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 maximal left atrial volume (LAVmax), minimal left atrial volume (LAVmin), left atrial volume contractile volume (LAVac) were obtained, the left atrial total emptying volume(LAVt), left atrial total emptying fraction(LAVtEF), left atrial passive emptying volume(LAVp), left atrial passive emptying fraction(LAVpEF), left atrial active emptying volume(LAVa), left atriam active emptying fraction(LAVacEF), conduit volume(CV), Contractile/Passive, Contractile/Total were obtained in the same way. Short-axis MPR at end-diastole was used for wall thickness measurement of the interventricular septum (ISVTd) and posterior wall (PWTd). LV inner diameter in end-diastole (LVIDd) was measured in the four-chamber MPR, while relative wall thickness (RWT) using the formula: RWT=(LVPWTd+IVSTd)/LVIDd. Then myocardial mass (MM), stroke volume(SV) and left ventricular ejection fraction(LVEF) were calculated directly using the left ventricular analysis software. All volumes indexs were standardized with body surface area (BSA). We determined the relationship between age and left atrial volume and fuction parameters, additionally analysed relation of left atrial volume and fuction to other clinical characteristics.Results:1. Monitoring change throughout the cardiac cycle of all participants, it was notes the left atrial volume achieved the minimum(end-diastole phase) at an RR interval of99.89+0.74%, immediately prior to atrial contraction(at the onset of P wave) at an RR interval of79.95+1.39%and maximum (end-systole phase) at an RR interval of40.33+1.24%. There are no significant correlations between the phases and the mean heart rate (r=0.11, P=0.915; r=-0.015, P=0.884; r=0.114, P=0.281). LAVmax=39.11±9.38ml/m2, LAVac=26.85+8.20ml/m2, LAVmin=17.40±5.67ml/m2。2. Age showed significantly correlation with some parameters:there was an age-dependent increase of LAVac, LAVa, LAVacEF, Contractile/Passive, Contractile/Total(r=0.504, P=0.000; r=0.648, P=0.000; r=0.521, P=0.000; r=0.706, P=0.000; r=0.729, P=0.000) and decrease of LAVpEF(r=-0.647, P=0.000). Age showed certain positive correlation with LAVmax, LAVmin(r=0.290, P=0.005; r=0.280, P=0.007) and negative correlation with LAVpEF,CV(r=-0.367, P=0.000; r=-0.209, P=0.045), but the correlation were not very strong. There are no significant correlations between age and LAVt,LAVtEF.Curve estimation showed the best fit model was Compound model for age and LAVa, and Cubic model for age and LAVac, LAVpEF, LAVacEF, Contractile/Passive, Contractile/Total. In order to further evaluate the relationship between age and 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 volume and function parameters were found among all age groups, LAVac, LAVmin, LAVa, LAVacEF, Contractile/Passive, Contractile/Total increased while LAVp and LAVpEF decreased with the increase of age. There were significant differences of every different volume and function parameters between each pair of age groups in multiple comparisons except LAVac between group<45years old and other three groups, LAVmin between group<45years old,45～54years old and55～64years old, LAVa, Contractile/Passive, Contractile/Total between group55～64years old and>64years old, LAVacEF between45～54years old,55～64years old and>64years old respectively. Even though there were no significant differences in LAVmax and LAVtEF, further comparations between each pair of age group showed that there were significant differences of LAVmax between group<45years old and>64years old, LAVtEF between group45～54years old and>64years old, group55～64years old and>64years old. all other comparisons for LAVt and CV showed no differences.3. There were no differences in all volume and function parameters between genders. Regarding smoking, there was increased LAVp(t=4.964, P=0.028), LAVa (t=15.349, P=0.000), LAVacEF(t=12.890, P=0.001),Contractile/Passive(t=8.526, P=0.004), Contractile/Total(t=5.044, P=0.027), while decreased LAVpEF(t=15.165, P=0.000) in current smokers compared to former or nonsmokers. There were no significant differences between high lipid level and normal lipid level for the volume and function parameters. SBP was associated with increased Contractile/Passive (r=0.206,P=0.049),Contractile/Total (r=0.210,P=0.049),but the correlation were not very strong. In correlation analysis, the relationship between BMI and left atrial volume and function showed no significant difference. Heart rate was negatively correlated with LAVmax(r=-0.270,P=0.009), LAVac(r=-0.330,P=0.001), LAVmin (r=-0.243, P=0.019), LAVa (r=-0.339, P=0.001), Contractile/Passive (r=-0.227, P=0.029) and positively correlated with LAVpEF (r=0.337, P=0.001) but the correlation was not very strong (r<0.5). DBP had no correlation with left atrial volume and function parameters. In further multiple regression analysis, LAVmax, LA Vac, LAVmin were independently associated with age and heart rate(R2=0.115, P=0.002; R2=0.317, P=0.000; R2=0.199, P=0.001). LAVp, LAVacEF, Contractile/Passive, Contractile/Total were independently associated with age and smoking status (R2=0.162, P=0.000; R2=0.350, P=0.000; R2=0.517, P=0.000; R2=0.468, P=0.000). LAVa, LAVpEF was independently associated with age, heart rate and smoking status(R2=0.521, P=0.000;R2=0.539, P=0.000). LAVt, CV was independently associated with age(R2=0.033, P=0.046; R2=0.033, P=0.045).Conclusions:1. EGG-DSCT can obtain the data of regular changes of the left atrial volume accompanied with the cardiac pulsation during cardiac cycle, so it is a feasible and novel modality to assess left atrial volume and function.2. Age is the major factor that influence and correlated significantly with left atrial volume and function. Left atrial passive emptying function decreases with age, while contractile emptying function increases. LAVmax remained unchanged until an extreme age(in our study,>64years old).3. Current smoking status is related to decreased passive emptying function, and high heart rate is related to smaller LAV and enhanced passive emptying function. In addition, there is relationship between SBP and left atrial function. Part two:Assessment of left atrial volume and function by dual-source CT in patients with essential hypertensionObjects:To investigate the volume and function properties of the left atrial as well as factors affecting these parameters in patients with essential hypertension with ECG-gated dual-source (DS) CT.Materials and Methods:92cases of subjects with essential hypertension (61males,31females, aged34～78years with a mean of58.48±10.91) 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 and whether with abnormal lipid levels or not, including the course of disease. Forty-five normal subjects with normal BP were selected from part one as control group(group N). The EH subjects were separated into two groups (52good controlled hypertensive group and40poor controlled hypertensive group) according BP controlled situation. Hypertensive patients were divided into3groups:normal left ventricular geometric models (group A), concentric remolding(group B), concentric hypertrophy(group C).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 left atrial volume and function to all clinical characteristics in order to observe which factors can influence the parameters. And then analysed the difference between EH subjects and normotensive controlled subjects, and the characteristics among the hypertensive patients with different patterns of left ventricular geometric models.Results:1. In EH subjects, there were no differences in all volume and function parameters between genders, current smokers and former or nonsmokers, hyperlipemia and normal lipid level. In correlation analysis, age showed significantly correlation with all the function parameters in all EH subjects. There was an age-dependent decrease of LAVp(r=-0.355, P=0.001), LAVpEF(r=-0.500, P=0.000) and the increase of LAVac(r=0.264, P=0.011), LAVa(r=0.379, P=0.000), LAVaEF(r=0.260^P=0.012),Contractile/Passive(r=0.619,P=0.000),Contractile/Total(r=0.570, P=0.000). The BMI was correlated with CV(r=-0.223, P=0.033), LAVtEF(r=-0.253, P=0.015), but the correlation was not very strong. SBP showed no relation to left atrial volume and function. DBP was correlated with LAVpEF(r=0.223, P=0.036), Contractile/Passive (r=-0.241, P=0.023),but the correlation was not very strong. Regarding heart rate, there was negatively correlated with LAVmax(r=-0.345, P=0.001), LAVac(r=-0.408, P=0.000),LAVmin(r=-0.465, P=0.000) and positively correlated with LAVtEF (r=0.391, P=0.000), LAVpEF(r=0.276, P=0.008), LAVaEF(r=0.279, P=0.007). The course of disease was negatively correlated with LAVp(r=-0.428, P=0.000), LAVpEF (r=-0.585, P=0.000), CV(r=-0.251, P=0.016),and positively correlated with LAVac (r=0.351, P=0.001), LAVa(r=0.499, P=0.000), LAVaEF (r=0.275, P=0.008), Contractile/Passive(r=0.722, P=0.000), Contractile/Total(r=0.669, P=0.000). In further multiple regression analysis, LAVmax, LAVac, LAVmin, LAVt was independently associated with age and the course of disease(R2=0.159,P=0.000; R2=0.345, P=0.000; R2=0.296, P=0.000; R2=0.177, P=0.000). LAVp was independently associated with age, high lipid levels and the course of disease(R2=0.235, P=0.000). LAVpEF was independently associated with age, heart rate, high lipid levels and the course of disease(R2=0.470, P=0.000). LAVa, CV, Contractile/Passive was independently associated with the course of disease (R2=0.222, P=0.000; R2=0.062, P=0.010; R2=0.263, P=0.000). LAVacEF was independently associated with age and heart rate (R2=0.128, P=0.001). Contractile/Total was independently associated with age and the course of disease (R2=0.386, 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 volume and function parameters were found to be significantly different between the two groups except LAVmax, LAVmin, LAVt and LAVtEF. LAVp, LAVpEF, CV were significantly lower in EH group when compared to control group while LA Vac, LAVa, LAVacEF, Contractile/Passive, Contractile/Totalwere higher, which means the passtive emptying functions of EH patients decreased and contractile emptying functions increased compared with 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. There were statistically significant differences between groups in respect to passive emptying function parameters. There were significant differences in LAVp, LAVpEF, Contractile/Passive when good controlled hypertensive group compared to the poor control group, LAVp, LAVpEF decreased in poor controlled hypertensive group while Contractile/Passive increased.4. Hypertensive patients were divided into4groups:normal left ventricular geometric models(group A), concentric remolding(group B), concentric hypertrophy (group C), eccentric hypertrophy(group D) was excluded because no subjects met the inclusion criteria. Compared with group N, there was significant difference between groups in respect to SBP, DBP, IVST, LVMI and RWT, In detail, the significant differences were identified in following comparisons:BMI, LVEDd, LVIDd increased in group B/C compared with N; LVEDd, IVST, LVIDd, RWT in group B with A; DBP, LVEDd, IVST, LVIDd, RWT increased in group C with A; LVMI increased in group C compared with B. There were no difference among the groups in respect to age and heart rate. LAVa, LAVacEF, Contractile/Total increased, while LAVpEF decreased in group A/B/C, compared with group N. There were significant differences among the groups. In detail, the significant differences were identified in following comparisons: group A with N, LAVac, Contractile/Passive increased; B with N, LAVp decreased while Contractile/Passive, LVEF increased; C with N, LAVac, LAVt, LVEF increased and LAVp, CV decreased. LVEF increased in group B compared with A,LAVac, LVEF increased while CV decreased in group C compared with A. Group C had higher LAVac and lower CV compared with group B. In all subjects, there was significant difference between groups in respect to LAVmax, LAVmin, LAVtEF and SV.Conclusions:1. In EH subjects, along with increasing course of disease, the passive emptying functions decreased and contractile emptying functions increased. Both the passive and contractile emptying functions increased when heart rate accelerated. Left atrial functions in subjects with EH decreases along with age growth. Hyperlipemia is related to lower the passive emptying functions in EH patients, which means we should realize the important of effective reduction of lipid levels.2. The differences between EH patients and normotensive subjects of left atrial functions indicated that before the changes of left ventricular geometric models, the LA functions decreased. Moreover, the differences of the state of hypertensive patients which were controlled by drug therapy influence the left atrial functions, which indicate monitoring the change of left atrial functions would help improve clinical medication.3. Left atrial function varied with left ventricular geometric.In normal left ventricular geometric and concentric remolding, the function of atrial reservoir and booster pump were enhanced to ensure left ventricular filling.However, left ventricular filling was mainly dependent on left ventricular dilatation.In concentric hypertrophy, left ventricular diastolic function was impaired severely. Then left ventricular filling depended mainly upon the function of left atrial reservoir and booster pump.4. ECG-gated DSCT can provide valuable assessment of left atrial volume and functions 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 left atrial, forming the real one-stop multi-function inspection and becoming a promising modality.