Objective: To detect correlation between systolic tissue velocity and left ventricular systolic dysfunction in patients presenting with severe rheumatic mitral regurgitation (MR). Methodology: A comparative study was performed at Punjab Institute of Cardiology, Lahore between October 2016 and February 2018. Fifty eight controls and 192 patients with rheumatic severe MR were included. End systolic dimension (LVESD), end diastolic dimension (LVEDD) and ejection fraction (LVEF) of left ventricle (LV) were taken. Group-1 contained healthy controls. Groups II, III and IV contained the patients of severe MR with non-dilated LV (LVESD ≤40mm and LVEF ≥60%), dilated LV (LVESD ≤40mm and LVEF ≥60%) and decreased LVEF (LVEF<60%) respectively. Tissue doppler was used to measure peak systolic tissue velocity at medial annulus (SV-Med), lateral annulus (SV-Lat) and average velocity (SV-Avg) of each subject. Results: A total of 250 study subjects contained 45.2% (n=113) males and 54.8% (n=137) females. Mean age of the study subjects was 30.8± 9.1. Group-I consisted of 58 controls. There were 69, 67 and 56 subjects in groups II, III and IV respectively. Moving from group-I to group-IV, LVEF decreased from 63.9%±2.2 to 46.2±6.5, LVESD increased from 23.2±2.3 to 49.0±2.9 and LVEDD increased from 45.9±3.5 to 64.3±3.6 respectively. Average systolic tissue velocity (SV-Avg) progressively decreased from group-I being 9.64±0.22 to group-IV being 6.32±0.47. There was a significant negative correlation between LV dysfunction and SV-Avg (spearman’s rank coefficient -0.921, p<0.001). A positive correlation was also found between LVEF and SV-Avg in patients with severe MR only (pearson’s coefficient 0.859, p<0.001). Conclusion: A significant negative correlation exists between the peak tissue systolic velocity and left ventricular dysfunction in patients presenting with severe rheumatic mitral regurgitation. Key words: Mitral Regurgitation, Tissue Velocity, Left ventricular dysfunction