Platelet function in blood from the coronary sinus in patients with arteriosclerotic heart disease.

Blood sampled from the coronary sinus was compared with blood collected simultaneously from the superior caval vein in 50 men with angiographically proven coronary heart disease. Primary, ADP-induced aggregation in coronary sinus blood was reduced by 14 per cent, collagen-induced aggregation by 10 and platelet retention by 16 to 30 per cent as compared with blood from the caval vein. The plasma levels of beta-thromboglobulin, platelet counts and number of circulating platelet aggregates were similar in parallel samples. The reduced platelet function in coronary sinus blood hardly reflects refractoriness after previous platelet stimulation, since no release or irreversible aggregation was induced. A reduced function might be the effect of direct depression induced in the coronary circulation. Most surprisingly, a selective thromboxane synthetase inhibitor (Dazoxiben) and acetylsalicylic acid normalized platelet aggregation but did not affect the low platelet retention response in coronary sinus blood. Thus, the reduced platelet function in coronary sinus blood is not only mediated via prostaglandins.