Role of angiographically identifiable thrombus on long-term luminal renarrowing after coronary angioplasty: A quantitative angiographic analysis

Background: Experimental studies suggest that mural thrombus may be involved in postangioplasty restenosis. The aim of our study was to examine the role of angiographically identifiable thrombus in the clinical situation. Methods and Results: The study population comprised 2950 patients (3583 lesions). The presence of angiographically identifiable thrombus either before or after the procedure was defined as the presence of a generalized haziness or filling defect within the arterial lumen. Restenosis was assessed by both a categorical (>50% diameter stenosis at follow-up) and a continuous approach (absolute and relative losses). The study population included 160 lesions with and 3423 lesions without angiographically identifiable thrombus. The categorical restenosis rate was significantly higher in lesions containing angiographically identifiable thrombus: 43.1% versus 34.4%, P<.01; relative risk, 1,449; CI, 1.051 to 1,997. The absolute and relative losses were also higher in lesions containing angiographically identifiable thrombus (absolute loss, 0.43 ± 0.66 versus 0.32±0.52; relative loss, 0.16±0.26 versus 0.13±0.21; both P<.05). The higher restenosis in these lesions was due primarily to an increased incidence of occlusion at follow-up angiography in this group: 13.8% versus 5.7%, P<.001. When lesions that went on to occlude by the time of follow-up angiography were excluded from the analysis, the restenosis rate between the two groups was similar by both the categorical (34.1% versus 30.4%, P = NS; relative risk, 1.183; CI, 0.824 to 1.696) and continuous (absolute loss, 0.23±0.46 versus 0.24±0.42, P = NS; relative loss, 0.09±0.17 versus 0.09±0.16, P = NS) approaches. Conclusions: Our results indicate that the presence of angiographically identifiable thrombus at the time of the angioplasty procedure is associated with higher restenosis. The mechanism by which this occurs is through vessel occlusion at follow-up angiography. Measures aimed at improving outcome in this group of patients should be focused in this direction.