Background:Impaired fibrinolysis, with imbalance between the key enzyme of plasminogen to plasmin activation, tissue plasminogen activator (tPA), and its main endogenous inhibitor, plasminogen activator inhibitor‐1 (PAI‐1), is shown to play a crucial role in thrombi formation which is an essential process in acute coronary syndrome (ACS). Most studies exist regarding myocardial infarction (MI). Limited investigations include patients with unstable angina (UA). However, no data is found concerning types of UA, namely, new‐onset angina (NUA) and progressive angina (PUA). Consequently, we investigated concentrations of tPA, PAI‐1 and tPA/PAI‐1 ratio in patients with above‐mentioned types of coronary artery disease (CAD).Aims:to compare the concentration of tPA and PAI‐1, tPA/PAI‐1 ratio in patients with different types of CAD (including NUA and PUA).Methods:In this cross‐sectional study, we collected blood samples in 94 patients with CAD ‐ 10 patients with MI, 57 patients with UA (38 patients with PUA and 19 patients with NUA), 27 patients with chronic coronary disease (stable angina (SA)). Concentrations of tPA and PAI‐1 were determined by standart method ELISA. Ratio tPA/PAI‐1 was calculated. There were no significant difference between groups of patients with respect of age, gender and body mass index.Results:In our study, we observed significant difference in tPA concentration (p = 0,0001) and tPA/PAI‐1 ratio (p = 0,004). However, PAI‐1 did not differ significantly in groups (p = 0,326), though it tended to be higher in patients with ACS in comparison with SA (0,392 (0,324‐0,472) U/ml vs 0,321 (0,284‐0,456) U/ml, p = 0,100). Unexpectedly, we identified the highest PAI‐1 concentration in UA group.Both tPA and tPA/PAI‐1 were significantly lower in ACS in contrast to SA (0,226 (0,173‐0,233) U/ml and 0,514 (0,432‐0,625) vs 0,234 (0,222‐0,295) U/ml and 0,619 (0,505‐0,997), p = 0,016 and p = 0,039, respectively).We detected significantly lower tPA concentration and tPA/PAI‐1 in patients with UA in comparison with SA (0,219 (0,173‐0,230) U/ml vs 0,234 (0,222‐0,256) U/ml, p = 0,002, and 0,485 (0,427‐0,597) vs 0,619 (0,505‐0,811), p = 0,021, respectively).Finally, we revealed significant difference in tPA concentration and tPA/PAI‐1 between NUA and PUA (p = 0,0001 and p = 0,001, respectively). Moreover, there were no difference between tPA concentration and tPA/PAI‐1 in MI and NUA (p = 0,071 and p = 0,756, respectively) as well as SA and PUA (p = 0,153 and p = 0,188, respectively). Additionally, the lowest tPA/PAI‐1 ratio was in NUA group.Summary/Conclusion:We have established imbalance between concentrations of tPA and PAI‐1 depending on CAD type. Thus, the highest thrombotic activity was detected in UA group while the lowest fibrinolytic activity was in NUA group. These findings call for further studies within types of UA as well as MI.image