Background:Cardiovascular diseases (CVD) are the top most cause of death in the world. As per world health organization (WHO), greater number of people die of CVDs than any other cause.Out of the CVDs predominant mortality is attributed to coronary artery disease(CAD) which includes stable CAD and unstable CAD (which can manifest as unstable angina, NSTEMI or STEMI) . Hence the present study was undertaken at our tertiary care centre to assess different indices of RV function by Echocardiography within 48 hours of onset of symptoms in 1st episode of acute IWMI and to correlate it with the site of lesion in CAG. Materials & methods:A hospital-based study was conducted with 100 patients of acute IWMI (1st episode) who had presented within 48 hours of symptoms. Patients were divided into two groups depending on the ST elevation in leads V4R or V3R (whether elevated or not): Group I: subjects showing ST elevation in V4R or V3R (IWMI with RVMI), andGroup II: subjects showing isoelectric ST in V4R or V3R (IWMI without RVMI). The following parameters were used for RV functional assessment-- 1. TAPSE (tricuspid annular plane systolic excursion) , 2. RVFAC (right ventricular fractional area change), 3. Pulsed wave tissue Doppler imaging (assess S’,ie, tricuspid annular velocity and MPI ,ie, myocardial performance index). These patients had undergone CAG to assess the site of lesion and its results was correlated with the RV indices.Statistical testing was conducted with the statistical package for the social science system version SPSS 20.0. Results:TAPSE (12.88±1.7 Vs 21.48±3.96),S’(9.14±1.14 Vs 16.14±2.40), RVFAC(30.86±3.6 Vs 47.18±7.2) were substantially low in patients in group I as compared to group II whereas Myocardial Performance Index - Tissue Doppler Imaging (MPI-TDI) (0.62±0.16 vs. 0.32±0.10; p<0.05) values was substantially more in Group I as compared to Group II according to the Student t-test.The TAPSE (13.95±3.16 cm vs. 20.98±4.5 cm; p<0.05), S’ (9.53±1.9 m/s vs. 15.9±2.6 m/s; p<0.05) and RV-FAC (30.96±3.3 vs. 47.12±7.4; p<0.05) values were compellingly lesser in cases with Proximal RCA Lesion whereas the MPI-TDI (0.66±0.11 vs. 0.31±0.07; p<0.05) values were higher in patients with Proximal RCA Lesion when compared to those without Proximal RCA Lesion as per Student ttest.For predicting proximal RCA lesion the cut off value of TAPSE < 16 showed Sensitivity of 87.5%, Specificity of 91.1%, Positive Predictive Value (PPV) of 82.3% and Negative Predictive Value (NPV) of 93.9%,the cut off value of S’ <10 cm/sec showed Sensitivity of 81.25%, Specificity of 92.6%, PPV of 83.8% and NPV of 91.3%,the cut off value of MPI-TDI >0.55 showed Sensitivity of 84.3%, Specificity of 92.6%, PPV of 84.3% and NPV of 92.6% and the cut off value of RV-FAC <35% showed Sensitivity of 87.5%, Specificity of 91.1%, PPV of 82.3% and NPV of 93.9%. Conclusion- Echocardiography is a valuable tool to assess right ventricular function and to diagnose RVMI with IWMI. Assessment of different echocardiographic parameters of RV function showed substantial difference amongst groups with or without Proximal RCA lesion proven by coronary angiography.