Antiplatelet drugs in the secondary prevention of myocardial infarction. One view of the present position

Vasoconstrictor activity of coronary sinus plasma from patients with coronary artery disease

Vasoactive properties of plasma samples taken from the coronary sinus, a systemic artery and the superior vena cava of 13 patients with angiographically proven coronary artery disease and from 5 patients with normal coronary arteriograms were assayed in vitro by measurement of the changes in tension of rings of isolated canine coronary arteries. Addition of 1 ml samples of platelet-rich plasma from the coronary sinus of patients with coronary artery disease into a 20 ml organ bath induced an initial relaxation followed by sustained constriction in bioassay coronary artery rings with endothelium and only vasoconstriction in rings without endothelium. The vasoconstrictor activity of the coronary sinus plasma showed positive correlation with the severity and extent of coronary artery narrowing. Systemic arterial and venous plasma samples from patients with coronary artery disease and the coronary sinus plasma from patients with no coronary artery disease evoked only endothelium-dependent relaxations. These vasoactive properties of the various plasma samples were similar whether the samples were taken during rest or during supine bicycle exercise. The serotoninergic receptor antagonist methiothepin prevented the vasoconstriction induced by the coronary sinus plasma samples. These data demonstrate that the coronary sinus blood of patients with atheromatous coronary artery disease exhibits vasoconstrictor activity that may be associated with 5-hydroxytryptamine (serotonin), presumably released from platelets.

Intracoronary platelet activation in ischemic heart disease: effects of ticlopidine

Plasma levels of platelet factor 4 have been measured in the aortic and coronary sinus blood of 35 patients: group I (n = 12) with normal coronary arteriograms; group II (n = 15) with angiographically proven coronary artery disease; and group III (n = 8) composed of patients with ischemic heart disease who were being treated with the antiaggregant agent ticlopidine at the time of cardiac catheterization. The mean increase in platelet factor 4 levels through the coronary circulation was 27.4 +/- 21.9 ng/ml (mean +/- standard deviation) in group II, compared with -1 +/- 4.5 ng/ml in group I (p less than 0.01). In group III plasma levels of platelet factor 4 in aortic and coronary sinus samples were all within the normal range. Thus, we conclude that platelet activation constantly occurs in the coronary circulation of patients with stable coronary artery disease, and can be prevented with ticlopidine.