768-4 What is Unique About the Infarct Related Artery and How Do These Features Influence Success During Direct PTCA for AMI

In spite of frequent presence of “high risk” characteristics, infarct angioplasty is not fraught With adverse procedural complications. We analyzed angiographic morphology of 103 consecutive AMI pts undergoing direct PTCA for its influence on procedural success. Using multivariate analysis lesion length (p = 0.002) and infarct related artery calcification (p = 0.001) were the only features predicting success. TIMI 3 reflow was predicted only by the residual flow grade (TIMI flow + collateral flow) prior to PTCA and not by either components alone. AMI lesions characteristics were compared with those in 154 pts undergoing PTCA for chronic CAD or unstable angina as shown in the table. LESION CHARACTERISTIC Control pts Pre PTCA AMIpts Pre PTCA AMI pts Post PTCA Irregular or ulcerated 2% 70% Clot 12% 69% ** 8% ‡‡ Haziness 12% 82% ** 56% ‡‡ % Stenosis Pre/Post 65%/30% 95% * 34% Incidence of Dissection 30% 17% ‡ Ave Dissection Length 4 mm 15 mm ‡‡ * p l 0.05; ** p l 0.01 Pre Vs Post AMI; ‡ p l 0.05. ‡‡ p l 0.01 AMI Pre Vs Post Conclusions Angiographic characteristics considered to be “high risk” for PTCA do not adversely affect procedural success in AMI, pointing to uniqueness of the underlying lesion. A paradoxically lower incidence but longer length of angiographic dissection after PTCA in AMI suggests that the nature of plaque rupture that leads to AMI is different from the injury induced by PTCA. Better luminal enlargement in spite of more severe initial stenosis is consistent with compression of soft plaque or thrombus as the principal mode of PTCA action in AMI. A significant transformation of morphology from high to low risk in a majority of pts undergoing direct PTCA for AMI may explain lowering of recurrent ischemia after direct PTCA. Unique angiographic characteristics can also predict TIMI 3 reflow as well as anatomic success for PTCA in AMI.