Clinical significance of plasminogen activator inhibitor activity in patients with exercise-induced ischemia

Thrombosis (clot formation) is well known to play a role in heart attacks, and is linked to severe angina as well. Angina is evidenced by a chest pain that results from transient coronary ischemia (loss of blood flow in coronary vessels). Thrombosis is regulated by the balance between the level of tissue plasminogen activator (t-PA), which is thrombolytic (breaks up clots), and tissue plasminogen activator inhibitor (PAI). Some studies have suggested that patients with unstable angina are deficient in t-PA, while others have found increased levels of PAI. Other factors, such as age and gender, are likely to be important as well. Exercise-induced ischemia and levels of t-PA and PAI were studied in 67 male patients over age 40. When measured during rest, PAI activity was significantly greater in patients with exercise-induced ischemia, and these levels at rest correlated with the extent of exercise-induced ischemia in this group of patients. Among the patients with angina, those with ischemia in multiple coronary blood vessels had lower increases in t-PA, lower PAI activity, and higher PAI activity during exercise. The study suggests that elevated PAI activity results from ischemia-induced cell damage and this may contribute to the risk of coronary occlusion. The results suggest that increased PAI activity may be an important indicator of the extent of ischemia in coronary artery disease. (Consumer Summary produced by Reliance Medical Information, Inc.)