Aspirin and dipyridamole in the prevention of acute coronary thrombosis complicating coronary angioplasty.

To test the hypothesis that pretreatment with adequate antiplatelet therapy reduces the likelihood of acute coronary thrombosis during routine percutaneous transluminal coronary angioplasty (PTCA), we reviewed, blinded to treatment group, the films and records of 300 consecutive initially successful PTCAs. Films before PTCA, immediately after, and at least 30 min after the last balloon inflation were assessed for the presence of any thrombus at the PTCA site. We excluded 37 patients who received streptokinase before PTCA or who had 100% occlusion or thrombus on pre-PTCA films. New thrombi were classified as clinically significant (defined as causing 100% occlusion or requiring emergency surgery or streptokinase therapy) or as not significant (not causing an acute problem or requiring intervention). Patients were classified into three groups, based on the type and extent of antiplatelet therapy received. Group 1 (no aspirin, n = 121) consisted of patients who did not receive aspirin either before admission or in hospital before PTCA (with or without dipyridamole). Group 2 (standard treatment, n = 110) received aspirin with or without dipyridamole but did not receive both drugs before admission and in hospital before PTCA. Group 3 (maximal treatment, n = 32) received both aspirin and dipyridamole before admission and in hospital before PTCA. New thrombi were detected at 39 (14.8%) PTCA sites, of which 15 (5.7% of all PTCA sites) were considered clinically significant. Group 1 had the highest incidence of both thrombus (21.5%) and clinically significant thrombus (10.7%). A reduction was seen in group 2 in thrombus (11.8%; p = .07) and in clinically significant thrombus (1.8%; p = .005). Group 3 had no thrombus (p = .001) and no clinically significant thrombus (p = .04). In addition to inadequate pretreatment with antiplatelet therapy, univariate analyses demonstrated several other risk factors for thrombus: higher percent diameter stenosis before PTCA (p less than .008), higher platelet count (p = .013), and current smoking (p = .03). Only higher platelet count (p less than .001) and inadequate pretreatment (p = .001) were associated with clinically significant thrombus. Stepwise logistic regression analysis demonstrated that for thrombus, the lack of effective antiplatelet therapy was the most discriminatory variable, followed by current smoking, higher percent diameter stenosis, and dissection. For clinically significant thrombus, once the lack of pretreatment with effective antiplatelet therapy was considered, no other factors added significant discriminatory information.(ABSTRACT TRUNCATED AT 400 WORDS)