Effects of serotonin on coronary arteries of cardiac transplant recipients.

Serotonin constricts coronary arteries with endothelial dysfunction. To detect early graft artery disease, the responses to intracoronary serotonin were studied 1 month (group A, 14 patients) and 1 year (group B, 13 patients) after orthotopic cardiac transplantation. No patient had evidence of rejection and all had angiographically normal coronary arteries. Serotonin in increasing doses (1, 10 and 20 micrograms/min for 2.5 minutes each) was infused into the coronary circulation. Diameters of proximal, middle and distal segments were measured by quantitative angiography. At the maximal concentration of serotonin, the diameters of the proximal segments decreased to 73 +/- 4% (percentage of the baseline) in group A; the diameters of the middle and distal segments decreased to 67 +/- 5 and 63 +/- 4%, whereas in group B, the diameters of the proximal, middle and distal segments were 90 +/- 6% (p < 0.02 vs group A value), 88 +/- 5% (p < 0.01 vs group A value) and 84 +/- 4% (p < 0.01 vs group A value), respectively. These changes were significantly (p < 0.02) different from those observed in 6 control patients in whom no constriction was induced by intracoronary serotonin. Moreover, coronary plasma endothelin levels were significantly higher in group A than in group B and control patients (5.6 +/- 0.3 vs 4.3 +/- 0.2 fmol/ml in group B and 3.9 +/- 0.3 fmol/ml in control patients). Thus, an abnormal response to intracoronary serotonin seems to occur often in transplant patients, and this abnormality is unexpectedly more pronounced in the early weeks after transplantation.(ABSTRACT TRUNCATED AT 250 WORDS)