LOCAL EFFECT OF SEROTONIN RELEASED DURING CORONARY ANGIOPLASTY

Background. Serotonin is released after the aggregation of platelets, a phenomenon that may occur after coronary angioplasty. We sought to determine whether serotonin is released into the coronary circulation during coronary angioplasty and to assess whether serotonin can affect coronary-artery tone during angioplasty. Methods. Blood samples were drawn from the ascending aorta and the coronary sinus of eight patients scheduled to undergo angioplasty of the left anterior descending or circumflex coronary artery. Samples were obtained before angioplasty and after each balloon dilation. The dimensions of arterial segments distal to the site of dilation were measured angiographically before angioplasty and 5 and 15 minutes after the last dilation in these eight patients and in seven similar patients; the latter group was treated with ketanserin, a serotonin(2)-receptor antagonist, before angioplasty. Results. Before the eight patients underwent angioplasty, their mean (+/-SE) plasma serotonin level in the aorta was 2.5+/-0.7 ng per milliliter and that in the coronary sinus was 2.3+/-0.6 ng per milliliter (P = 0.34). The seretonin level in plasma from the coronary sinus rose significantly, to 31.5+/-13.5, 17.6+/-5.3, and 29.1+/-8.1 ng per milliliter after the first, second, and third dilations, respectively (P = 0.014 for the comparison with preoperative levels). In contrast, the serotonin level in plasma from the ascending aorta did not change. The cross-sectional area of the coronary artery was significantly reduced 5 and 15 minutes after the last dilation (from a preoperative value of 3.7+/-0.5 mm(2) to 2.7+/-0.4 mm(2) 15 minutes after the last dilation; P = 0.011). This vasoconstriction was significantly blunted in the seven patients who received ketanserin (from 3.7+/-0.5 mm(2) before angioplasty to 3.9+/-0.4 mm(2) after 15 minutes) (P = 0.017 for comparison with the eight patients who did not receive ketanserin). Conclusions. Serotonin is released into the coronary circulation during angioplasty, and this vasoactive substance may contribute to the occurrence of vasoconstriction distal to the dilated site. The vasoconstriction is attenuated by ketanserin, a serotonin(2)-receptor antagonist.