Ischemia in Patients With Angina Pectoris

Background. The complement system and arachidonic acid metabolites are involved in severe myocardial ischemia such as myocardial infarction. Furthermore, there is experimental evidence for C5a participationin thromboxane production. Methods and Results. We examined whether C5a and thromboxane are produced during brief and reversible episodes of myocardial ischemia induced in patients with stable angina. Twenty-five patients underwent either atrial pacing or percutaneous transluminal coronary angioplasty associated with arterial and coronary sinus blood sampling. Rapid atrial stimulation of patients with effort angina caused significant ST segment depression (A ST= -1.7+0.2 mm), decreased fractional lactate extraction (from +12.8±2.5% baseline to -13.7±4.6% at peak ischemia, n=13, p<0.001), and increased coronary sinus plasma thromboxane B2 levels (from 345±85 pg/ml baseline to 1,684±64 pg/ml at peak ischemia, p<0.01). Changes of fractional lactate extraction correlated significantly with changes of coronary sinus plasma levels of thromboxane B2. There was no change of coronary sinus 6-keto-PGFl,i levels. Similar pacing of control subjects (n=6) did not cause release of lactate or thromboxane. Seventeen other patients underwent exercise testing with noninvasive measurements of thromboxane and prostacyclin metabolites in urinary samples collected before and after the test. No detectable increase of urinaryll-dehydrothromboxane B2 was measuredin patients with stable angina after exercise-induced myocardial ischemia. However, basal11-dehydrothromboxane B2 levels were significantly higher in patients with angina (105±25 pg/mmol creatinine, n=9) than in control patients (45±8 pg/mmol creatinine, n=8, p<0.05 between groups). Coronary sinus plasma levels of the anaphylatoxin C5a always remained below 4 ng/ml in patients undergoing pacing. More severe myocardial ischemia after coronary angioplasty (percent lactate extraction decreased from +24.8+2.7% baseline to -41.6+22.4%o at peak ischemia, p<0.05) was not associated with C3a or C5b-9 generation. In all patients, there was neither platelet sequestration nor plateleta-granule release (no changes of f-thromboglobulin/platelet factor 4 levels) into the coronary sinus plasma. Conclusions. Patients with stable angina have chronically increased thromboxane synthesis as assessed by excretion of urinary metabolites. Thromboxane is acutely released into the coronary sinus during pacing-induced ischemia without significant intracoronary platelet aggregation. Complement does not appear to be activated in stable angina during brief and reversible episodes of myocardial ischemia and does not contribute to thromboxane production. (Circulation 1991;84:2054-2062)