Thromboxane A2 in acute myocardial infarction.

We evaluated the presence of thromboxane B2, the stable metabolite of thromboxane A2, early in the course of acute myocardial infarction (AMI) in both animal and patient studies. In an open-chest model, the left anterior descending artery (LAD) was isolated and the great cardiac vein was cannulated in nine dogs. Following occlusion of the LAD, there was an increase in thromboxane B2 concentration from 0.77 +/- 0.0093 to 1.79 +/- 0.46 pmol/ml (p less than 0.05) and 1.96 +/- 0.48 pmol/ml (p less than 0.05) at 1 and 5 minutes, respectively, following coronary occlusion. At 30 and 60 minutes after occlusion there was no significant increase compared to the baseline. In 17 patients with AMI the mean thromboxane B2 concentration was 0.96 +/- 0.13 pmol/ml at 4.88 +/- 0.40 hours after the onset of chest pain. In 12 patients with sequential samples before and after restoration of patency of the occluded vessel, the initial concentration was 0.71 +/- 0.058 pmol/ml. At 5 minutes after restoration of patency thromboxane B2 concentration was 1.1 +/- 0.17 pmol/ml (p = 0.05). One hour later a return to baseline was noted (0.82 +/- 0.75 pmol/ml). Two patients with the highest thromboxane B2 concentrations (2.0 and 2.6 pmol/ml) were unable to have successful recanalization. We conclude that generation of thromboxane A2 occurs during the early stages of AMI and may be an important pathophysiologic phenomenon in AMI.

Combination therapy for evolving myocardial infarction: intracoronary thrombolysis and percutaneous transluminal angioplasty.

Nonsurgical coronary reperfusion for evolving myocardial infarction is a promising new technique for the salvage of jeopardized myocardium. Successful reperfusion can be established by intracoronary infusion of streptokinase in approximately 75 percent of patients within the first 6 hours of transmural infarction [1.2]. Following recanalization, most patients are left with high grade fixed coronary stenoses which are potential sites for recurrent thrombus formation. Since the underlying site for coronary thrombosis is still present, reocclusion may occur. Indeed, early experience suggests that recurrence of thrombosis is not uncommon [3.4]. Therapy for evolving myocardial infarction should, in some patients, involve not only thrombolysis, but also an attack on the fixed coronary lesion. We describe a patient wit evolving myocardial infarction who was treated successfully with combination therapy consisting of intracoronary streptokinase followed by percutaneous transluminal coronary angioplasty [5].