Quantification of Coronary Inflammation Using Fat Attenuation Index (FAI) in Indians: A Retrospective Study

Background: Asian Indians have the highest prevalence (11%) of coronary artery risk worldwide compared to all other races. So far no quantifiable risk factor has been shown to explain such a high prevalence. Fat attenuation index (FAI) using CT coronary angiography (CTCA) has been recently used to demonstrate coronary perivascular inflammation and to confirm that atherosclerosis is an inflammatory process. Hence this study was conducted to determine FAI using CTCA in 200 adult Indians as a retrospective study to determine if it can be the answer to establish the cause for high prevalence of CAD in Indians and whether there are differences in FAI in normal adults and those with significant CAD and to determine if it could be used as imaging biomarker for diagnosis and follow up of such patients. Material and Methods: Retrospective study of 200 patients who underwent CTCA was done. Patients were divided into two groups based on no coronary disease (NOCAD) and those with significant coronary artery disease (CAD). Patient demographics were recorded for both groups. FAI estimation was done along with Plaque volume index (PVI), pericardial volume estimation and the differences between the two groups were statistically analysed. Results: Mean patient age in both groups was 52 years with male predominance (75-80%). Mean FAI,s for left anterior descending and right coronary arteries was 45.4 and -44.7 HU and of -38.0 and -39.2 HU for NOCAD and CAD groups respectively (p -38HU was 73% and 80% respectively with LR of 3.6. Conclusion: Normal adult Indians with NOCAD showed a high FAI compared to all other races which could be reason for highest prevalence of CAD amongst Indians. FAI can be used as imaging biomarker to differentiate CAD from NOCAD with sensitivity and specificity of 73% and 80% respectively.