Fibrin formation and platelet activation in patients with myocardial infarction and normal coronary arteries.

Coronary spasm is the mechanism most often postulated to explain the rare combination of myocardial infarction and angiographically normal coronary arteries, although the reported evidence for its role is circumstantial rather than conclusive. Whereas the importance of thrombosis in myocardial infarction is uncontested in the presence of significant coronary artery disease, there is little in vivo evidence for thrombosis in angiographically normal coronary arteries. Among 11 consecutive patients with acute myocardial infarction undergoing thrombolytic therapy with recombinant tissue plasminogen activator (rtPA) 3.2 +/- 0.7 h after onset of chest pain, and angiography 10.2 +/- 4.5 days later, three young men had normal coronary arteries. Their cases are documented electrocardiographically, enzymatically and angiographically. Mean plasma levels of fibrinopeptide A (FPA) and beta-thromboglobulin (BTG) were clearly elevated before and during rtPA therapy: FPA 52 +/- 41 ng ml-1, BTG 257 +/- 46 ng ml-1. They did not differ significantly from corresponding mean plasma levels in the eight patients with severe coronary artery disease: FPA 67 +/- 66 ng ml-1, BTG181 +/- 75 ng ml-1. We conclude that fibrin formation and platelet activation are probably equally important in the early hours of myocardial infarction, whether or not significant coronary artery disease is present.