Slow coronary flow (SCF) is a well recognized clinical entity, characterized by delayed opacification of coronary arteries in the presence of normal coronary angiogram. There is currently no data evaluating myocardial systolic function in SCF phenomenon. This study was performed to evaluate regional and global systolic function using tissue Doppler imaging (TDI), strain (S) and strain rate imaging (SRI) in patients with slow coronary flow. A total of 35 patients with slow coronary flow and otherwise normal coronary arteries (mean age 48 +/- 7 years) (SCF group) and 21 patients with normal coronary angiograms (mean age 50 +/- 12 years) (control group) were included in the study. These patients were prospectively assessed for evaluation of regional and global left ventricular function by conventional echocardiography, systolic TDI, peak S, and peak systolic strain rates (SRs) There was a significant difference in peak SRs (-1.1 +/- 0.2 vs. -1.8 +/- 0.2 1/s, P <= 0.0001) but similar in systolic TDI (42 +/- 20 vs. 44 +/- 21 mm/s, P = 0.77) and S (20.7 +/- 7.7 vs. 23.7 +/- 8.8, P = 0.14) between groups. SRs showed a good correlation with mean TIMI frame count (r = -0.80, P <= 0.0001). As the number of coronary artery with SCF increased global strain rate decreased further. In case of one or two or three coronary artery with SCF global strain rates were 1.4 +/- 0.2; 1.1 +/- 0.3; 0.9 +/- 0.2 1/s, respectively, P B 0.0001. Although ejection fraction was preserved, global and regional strain rate were decreased in SCF. In brief, there is an impairment in longitudinal left ventricular systolic function in patients with SCF.