Quantitative Assessment Of Epicardial Fat By Echocardiography

Objective:Epicardial adipose tissue is an intrinsic adipose tissue deposited on the surface of heart,which has special anatomical,physiological and biochemical characteristics and secretes a variety of adipocytokines.In recent years,a growing body of research has revealed that epicardial adipose tissue is closely related to the occurrence,development and prognosis of arteriosclerosis,atrial fibrillation,coronary heart disease,metabolic syndrome,cardiac insufficiency and other diseases.Cardiac enhanced CT is currently considered to be the preferred imaging modality for the assessment of epicardial fat.In this study,two-dimensional Echocardiography measures the the epicardial fat thickness at multiple sections to comparing the differences in epicardial fat thickness at each site.And then compared with the epicardial fat thickness measured by cardiac enhanced Computed Tomography at the same section and epicardial fat volume measured by cardiac enhanced Computed Tomography,and then we investigate the differences,correlation,consistency,and repeatability between ultrasound and cardiac enhanced CT in the assessment of epicardial fat content.In order to provide a new auxiliary examination index for clinical practice and research.Methods:A total of 81 subjects who underwent echocardiography and cardiac enhanced CT in Peking University Shenzhen Hospital from December 2020 to February 2021 were enrolled,including 41 males and 40 females,aged from 27 to 82 years,with an average of 63.06±12.14 years.Basic demographic information such as age,gender,height,and weight and lifestyle habits such as smoking and alcohol consumption and previous medical history such as coronary heart disease,atrial fibrillation,hypertension,diabetes,hyperlipidemia,and renal insufficiency were recorded.Pregnant and lactating women,patients with moderate and above pericardial effusion,organic valvular heart disease,severe cardiac insufficiency,tumors and cachexia,and previous history of coronary artery bypass grafting(CABG)and coronary intervention(PTCA)were not included in this study.Echocardiography was performed using a Mindray M9 portable color Doppler ultrasound diagnostic apparatus equipped with a SP5-1s cardiac ultrasound probe(frequency of 1 – 5 MHz),routine transthoracic echocardiography was performed according to the American Society of Echocardiography criteria.The parasternal left ventricular long-axis view,parasternal papillary muscle level left ventricular short-axis view,apical four-chamber view,and subxiphoid four-chamber view were taken to measure the epicardial fat thickness beside the right ventricular free wall,right atrioventricular groove,apical notch interventricular groove and apex at the end of systole.The measurement was perpendicular to the heart surface taking the maximum thickness from the myocardium to the visceral pericardium.Cardiac enhanced CT was performed using a Siemens dual-source CT scanner in Germany(SOMATOM Definition Flash;Siemens Healthcare,Erlangen,Germany)to scan the subjects,using prospective ECG-gated scanning technique,intravenous contrast agent was injected through the distal upper limb vein or median cubital vein,images were acquired and stored.After the end of the scan,the original images were reconstructed at a slice thickness of 0.625 mm and 75% R-R interval importing into syngo.via VB 2.0(Siemens Healthcare)post-processing workstation.The epicardial fat volume is automatically derived and manually adjusted and epicardial fat thickness was measured at each site with reference to echocardiographic measurement methods.SPSS 23.0 software was used for data analysis,and D-W test(Kolmogorov-Smirnov and Shapiro-Wilk test)was used for normality test for all continuous variables.Normally distributed continuous variables were expressed as mean± standard deviation,and classified variables were expressed as absolute numbers and percentages.The significance of difference was analyzed by paired sample t test,the correlation analysis was performed by Pearson correlation,and the consistency analysis was performed by Bland-Altman method,in order to analyze the difference,correlation and consistency of epicardial fat assessment by echocardiography and cardiac enhanced CT.P < 0.05 was considered statistically significant.Thirty subjects were randomly selected for the repeatability test and the inter-observer and intra-observer agreement were analyzed by interclass correlation coefficient(ICC).Results:(1)Differential analysis: The epicardial fat thickness measured by ultrasound beside the right ventricular wall in the parasternal left ventricular long-axis view was greater than the CT value(P < 0.05),the epicardial fat thickness measured beside the right ventricular wall in the left ventricular short-axis view at the parasternal papillary muscle level was close to the CT value(P > 0.05),and the epicardial fat thickness measured at the right atrioventricular groove in the subxiphoid four-chamber view,the epicardial fat thickness measured at the interventricular groove in the apical four-chamber view,and the epicardial fat thickness measured at the apex in the apical four-chamber view were smaller than the CT value(P < 0.05).(2)Correlation analysis:(1)Correlation between epicardial fat thickness measured by echocardiography and cardiac enhanced CT: There was a good correlation between epicardial fat thickness measured by echocardiography and cardiac enhanced CT at the parasternal left ventricular long axis,parasternal papillary muscle level left ventricular short axis,apical four-chamber heart(apical notch interventricular groove),and apical four-chamber heart(apex)views,but there was a very weak correlation at the subxiphoid four-chamber heart(atrioventricular groove)view.(2)Correlation between epicardial fat thickness measured by echocardiography and epicardial fat volume measured by cardiac enhanced CT: There was a good correlation between epicardial fat thickness measured by echocardiography and epicardial fat volume measured by cardiac enhanced CT at each site.(3)Correlation between epicardial fat thickness and epicardial fat volume measured by cardiac enhanced CT : There was a good correlation between epicardial fat thickness and epicardial fat volume measured by cardiac enhanced CT at the parasternal left ventricle,parasternal papillary muscle level left ventricular short axis,and apical four-chamber heart(apex),while there was a weak correlation at the subxiphoid four-chamber heart(atrioventricular groove)and apical four-chamber heart(apical notch interventricular groove).(3)Consistency analysis: There was good agreement between epicardial fat thickness measured by echocardiography and cardiac enhanced CT at the parasternal left ventricular long axis,parasternal papillary muscle level left ventricular short axis,apical four-chamber heart(apical notch interventricular groove),and apical four-chamber heart(apex),but poor agreement at the subxiphoid four-chamber heart(atrioventricular groove).(4)Repeatability analysis: The measured values of epicardial fat thickness measured by echocardiography and cardiac enhanced CT at each site all showed high repeatability.Conclusion:(1)The epicardial fat thickness near the right ventricular wall measured by echocardiography at was the closest The epicardial fat thickness beside the right ventricular wall measured by echocardiography in the parasternal papillary muscle level left ventricular short axis was the closest to that measured by cardiac enhanced CT.(2)There were good correlations and consistencies between epicardial fat thickness measured by echocardiography and cardiac enhanced CT,epicardial fat thickness measured by echocardiography and epicardial fat volume measured by cardiac enhanced CT,epicardial fat thickness measured by cardiac enhanced CT and epicardial fat volume at the parasternal left ventricular long axis,parasternal papillary muscle level left ventricular short axis,and apical four-chamber heart(apex)views,and both imaging techniques had high reproducibility.(3)The measurement of epicardial fat thickness by echocardiography is an effective and reliable alternative evaluation method,selecting the parasternal papillary muscle level left ventricular short axis view is the most accurate.