Antihypertensive drugs and fibrinolytic function

Abstract

Impaired fibrinolytic function, characterized by increased plasminogen activator inhibitor type 1 (PAI-1) levels and decreased tissue plasminogen activator (t-PA) activity, has been found in patients with hypertension and may account in part for the increased risk of atherosclerosis and its clinical complications in these patients. Failure to correct this prothrombotic state may be one of the possible reasons for the disappointing effect of antihypertensive treatment on the incidence of coronary events. In this regard, data from the literature indicate that different antihypertensive drugs may vary in their influence on fibrinolysis. Scarce and conflicting data exist regarding the effects of diuretics and beta-blockers on the fibrinolytic system. Angiotensin-converting enzyme (ACE) inhibitors (ACE-I) have generally been shown to improve the fibrinolytic balance by reducing plasma PAI-1 levels, calcium channel blockers (CCB) have been reported to increase t-PA activity, and angiotensin receptor blockers (ARB) seem to be neutral in their effect. Interesting data have been reported about the positive impact on fibrinolysis of combining an ACE-I with a CCB, which resulted in a decrease of PAI-1 caused by ACE inhibition, and an increase in t-PA resulting from calcium channel blockade. The positive effect of ACE-I on the fibrinolytic system has been related to: 1) inhibition of angiotensin II, which stimulates PAI-1 expression; 2) inhibition of degradation of bradykinin, a potent stimulus for tPA production; and 3) improvement of insulin sensitivity. The mechanisms underlying the CCB effect on t-PA are less clear, but a direct action of CCB on vascular endothelium has been reported to play a major role. The greater improvement in the fibrinolytic balance because of the combined action of ACE inhibition and Ca antagonism represents a further indication to the use of combinations of ACE-I and CCB in the treatment of hypertension.