Coronary angioscopic findings in the infarct-related vessel within 1 month of acute myocardial infarction - Natural history and the effect of thrombolysis

Background-Limited angioscopic information is available on the natural of infarct-related plaque after myocardial infarction (MI), in particular the effect of thrombolysis. Methods and Results-We studied with angioscopy the morphological characteristics of the infarct-related lesions in 56 patients between 24 hours and 4 weeks after MI. Forty of these patients were initially treated with a thrombolytic agent. Most lesions were complex (complex+ulcerated shape=54%). The predominant color of the plaque was yellow in 79% of cases; only 6% were uniformly white. Angioscopically visible thrombus was found in 77% of cases. Despite angioscopic evidence of instability, only 7% of the patients had post-MI angina. During the 1-month time window since the occurrence of MI, there was no significant difference in the angioscopic appearance of the plaque except for a slight increase in uniformly white plaques (P=.07). The use of a thrombolytic agent at the onset of MI was associated with a reduction in thrombus size and less protruding thrombi (P=.02) but not with a decreased frequency of plaque containing thrombi. Furthermore, a trend for more frequently ulcerated plaques (45% versus 16%, P=.06) was associated with the use of a thrombolytic agent. Conclusions-These results suggest that healing the infarct-related lesion requires more than 1 month and that an "ustable" yellow plaque with adherent thrombus is common during that period. This finding may partly explain the unique behavior of recent infarct-related lesions, which are more prone to occlude that other lesions.