Anti-Platelet Treatment of Middle-Sized Abdominal Aortic Aneurysms

The physiological transport in the aortic wall occurs mainly by centrifugal convection from the lumen to the adventitia through the arterial wall. Enlargement of an abdominal aortic aneurysm (AAA) is usually associated with the development of an intraluminal mural thrombus (ILT). The interface between the luminal side of the thrombus and flowing blood is a site of constant thrombus renewal, which is linked to platelet aggregation-induced fibrin generation and accumulation. In addition, red blood cells are entrapped causing an oxidative response. Through centrifugal convection are factors increasing the inflammatory and degenerative response transported from the ILT to media and adventitia. Two experimental studies on rats with experimental AAA have shown that aneurysmal progression can be impaired by antiplatelet agents. By a systematic literature search, 4 human cohorts were identified analysing the effect of antiplatelet treatment on the progression of AAA. The two largest cohorts couldn´t detect any significant difference. However, the cohorts included very small AAA, in which ILT seldom is present. In the two other trials, only testing AAA sized above 35 and 39 mm, respectively, use of low dose aspirin was associated with significantly lower expansion rates and less need for later surgical repair. Size-based subgroup analyses from relevant existing cohorts ought to be conducted for confirmation. Finally, low dose aspirin is recommend as general cardiovascular secondary prevention, however, large-scaled trials comparing low dose aspirin with more potent antiplatelets would be relevant.