CIRCADIAN PATTERNS OF PLASMA T-PA AND PAI-1 ANTIGEN LEVELS IN PATIENTS WITH SEVERE PERIPHERAL ATHEROSCLEROSIS

Raised plasma PAI-1 and t-PA antigen levels are known risk factors for acute coronary events. It is not known whether these factors are rela ted to coronary thrombosis or to a possible atherosclerotic background . Both factors show a marked circadian variation in blood. To assess t he effect of atherosclerosis on the fibrinolytic balance, we measured plasma t-PA and PAI-1 antigen levels 3-hourly for 24 hours in 7 patien ts with severe atherosclerosis (AS group) and in 10 healthy controls ( C). Age of AS and C did not differ significantly, In both AS and C, t- PA and PAI-1 levels were highest between 3:00h and 9:00h, and lowest b etween 18:00h and 24:00h. The 24h-averaged level of t-PA (median and i nterquartiles) was significantly higher in AS than in C [13.8 (10.5-16 .0) vs. 7.3 (4.7-7.9) mu g/L, p=0.002], The 24h-averaged level of PAI- 1 also tended to be higher in AS vs, C, but the difference did not rea ch statistical significance [17.9 (17.3-20.8) vs. 13.7 (10.3-18.6) mu g/L, p=0.09]. In C, but not in AS, t-PA levels correlated significantl y with those of PAI-1 (r=0.37, p=0.0001 in C vs. r=0.05, p=0.9 in AS). Thus, patients with severe AS, compared with C, have significantly hi gher plasma concentrations of t-PA antigen throughout the 24 hours, wh ich are not correlated to PAI-1. The association between raised t-PA a ntigen and coronary events may be mediated by underlying atheroscleros is.