Echocardiographic Detection Of Early Diabetic Heart Disease Using Integrated Backscatter And Doppler Tissue Imaging

IntroductionA number of experimental, pathologic, and epidemiologic studies support the existence of diabetic cardiomyopathy. At present, there are still no diagnostic criteria for it and it only can be considered when the other known cardiac diseases have been excluded. The clinical diagnosis of diabetic cardiomyopathy is made when systolic and diastolic left ventricular dysfunctions are present in diabetic patients without other known cardiac disease. The cardiomyopathy may be an important contributor to the susceptibility of diabetic subjects to the development of heart failure and to their worse outcome with this condition. As treatment to reverse this disorder is more likely to be effective before it goes to the point of no return of dilated cardiomyopathy, detecting diabetic cardiomyopathy at an early (preclinical) stage is very important. This study applied Integrated Backscatter Imaging (IBS) and Doppler Tissue Imaging ( DTI) techniques to discover the structural and functional disturbances and correlation of the structure and function of left ventricle in order to evaluate the diagnostic values of the techniques and search for clues of the main pathologic basis of diabetic cardiomyopathy.Materials and method1. Subjects (1)Patients studied. Thirty - five patients with diabetes were consecutivelyrecruited from the Department of Endocrinology in the 1st Affiliated Hospital of China Medical University from June to September in 2004. All patients were a-symptomatic and had an ejection fraction > 50% as assessed by the modified biplane Simpson's method with no history of coronary artery disease (CAD). After history, physical and laboratory examination, ECG, exercise stress test, standard echocardiography and other examinations, the patients would be excluded if they had the evidence of CAD, artery hypertension,, valvular disease, arrhythmias , congenital heart disease and noncardiac diseases (thyroid disease, chronic alcoholism, anemia) that may influence the heart. Of the thirty -five patients included (21 male, 14 female, mean age 50 ± 12 years, mean duration 3.6 ±4. 1 years) , two patients had autonomic neuropathy and one patient had retinopathy.(2) Controls. Twenty healthy subjects were selected from a "973" National Science Program which aimed to evaluate the aging process of normal people. Controls (12 male, 8 female, mean age 51 ±8 years) were age and gender -matched to the diabetic patients studied.2. Acquisition and data analysisWe used a standard commercial ultrasound machine ( HP Sonos 5500) with a 2. 0 -4. 0 MHz phased array probe, which was equipped with the standard commercial softwares of AD - IBS and DTI and had a drive for magneto optical disk. All the following examinations were accompanied with ECG; all images were saved for three consecutive cardiac cycles and each representative value was obtained from the average of three measurements.(1)Standard two - dimensional and Doppler ultrasoundSubjects were in the left lateral decubitus position and images were obtained in the standard apical four - champer view of left ventricle. Mitral inflow velocities were recorded by using conventional pulsed - wave Doppler echocardiography, positioning a sample volume at the level of the mitral leaflet tips. The peak early diastolic velocity (E) , peak late diastolic velocity ( A) , E/A ratio were measured. The ejection fraction (EF) was computed using a modified Simpson' s biplane method.(2) Tissue Doppler imagingIn the left lateral decubitus position, pulse tissue Doppler function was activated after a two - dimentional view of high quality was obtained. The gain and filter of Doppler were lowed appropriately and the velocity of scan was set to lOOmm/s. Data were acquired in the three apical views ( apical four - chamber, two -chamber, and long —axis views) to assess myocardial long-axis function. The angle between the scan - line and wall was controlled under 20° and the images were saved at the end of breath. The sample volume was put on the mitral annulus and the basal segment of each of six walls ( septal, lateral, an-teroseptal, posterior, inferior and anterior left ventricular walls) respectively, so that myocardial velocities were acquired. The peak systolic velocity (Sa) , peak early diastolic velocity (Ea), peak late diastolic velocity (Aa) at each point were measured. The mean velocity of mitral annulus and the basal segments were obtained from the average measurements of six left ventricular ( LV) walls. The Ea/ Aa ratio was defined as the ratio of the mean Ea and Aa.(3) Integrated Backscatter techniqueParasternal long - axis view of LV was obtained in a left lateral decubitus position. Total, time and lateral gains were adjusted to make endocardium best showed and this setting was kept constant after the IBS was activated. A 31 x31 pixel sample volume of crescent shape was put in the basal septum, posterior wall or pericardium under the same scan -line. The position of the sample volume was checked and adjusted in each frame to keep the sample volume within the same region during the whole cardiac cycle. Average image intensity (AH) and cyclic variation in IBS (CVIB) on the three positions were measured. Calibrated IBS (IBS% ) was obtained by subtracting pericardial All from the one of the septum or posterior wall.3. Statistical analysis. Values were expressed as mean ± standard deviation. Independent - samples T test was used to compare the difference between two groups. Data were analyzed using standard statistical software ( SPSS11.0). A p value of <0.05 was considered statistically significant.Results1. Clinical and standard echocardiographic characteristicsPatients and controls have comparable age, gender, E, E/A ratio and EF. Diabetic patients showed a higher A value than controls ( p <0.05).2. Comparison of IBSIBS% of the septum is greater in diabetic group than in controls ( p < 0. 05) ; patients' CVIB of posterior wall is less, compared with controls(p <0. 01). There were no significant differences in IBS% of the posterior LV wall and CVIB of the septum between two groups.3. Comparison of DTI(1) Parameters of diastoleParameters of diastole including each Ea, Aa of six walls at mitral annulus and the basal segment of LV, mean Ea and Aa of six walls and the Ea/ Aa have no significant-differences between the two groups.(2) Parameters of systoleSa at mitral annulus of inferior and anteroseptal LV walls, Sa at the basal segment of anteroseptal LV walls and the mean Sa of six walls decreased significantly in patients than in controls ( p < 0. 01, p < 0. 01, p < 0. 05, p < 0. 01, respectively ). There were no significant differences in the otherLV parameters of systole between two groups.4. The correlation of IBS and DTISa at mitral annulus of anteroseptal and inferior LV wall correlated moderately conversely with IBS% of the septum ( r = - 0. 524, p < 0.01; r = - 0. 506, p <0. 01, respectively). However, Sa at mitral annulus of inferior LV wall and Sa at the basal segment of anteroseptal LV wall have low negative correlation with IBS% of the septum (r= -0.383, p<0.05; r= -0.316, p<0. 05, respectively). There are low positive correlations between CVIB of posterior LV wall and Sa at the mitral annulus of inferior LV wall and the mean Sa at the annulus ( r = 0.469, p <0.01; r = 0.415, p <0.01, respectively).