The Role of Platelets and Aneurysm Thrombus in the EVAR Post Implantation Syndrome

Post implantation syndrome (PIS) is a well-defined entity with unclear etiology, complicating a number of patients with abdominal aortic aneurysms treated with endovascular aortic repair (EVAR). The aim of this study was to assess the platelets' role and the influence of aneurysmal sac thrombus volumes in the development of PIS. A retrospective analysis of prospectively collected data was performed, and 76 patients who were treated by EVAR (2011-2013) were studied. Aneurysms with endoleak were not included in the study. Based on the criteria for systemic inflammatory response syndrome (SIRS), 17 patients (22%) developed PIS (which is considered a SIRS analogue), while 59 (78%) did not.

The 2 groups were compared in relation to the following parameters: baseline platelet count (PLT), decrease of platelet count (PLT drop), volume of the arterial flow before the procedure (V flow), volume of thrombus of the aneurysm (V thromb), ratio of thrombus volume to aneurysm sac volume (V ratio), and the volume of newly formed thrombus (V new). Volume flow measurements were calculated by Osirix software preoperatively and in the first month postoperatively. Parametric and nonparametric techniques (unpaired t-test, Mann-Whitney U test) were used accordingly.

Baseline platelets absolute count was greater in the PIS group (239,000 ± 17,000) versus the non-PIS group (194,000 ± 6,900, P = 0.004), and the PLT drop was larger in the PIS group (74,000 ± 15,600 versus 45,000 ± 5,300, P = 0.019). No difference was found regarding the aneurysm volumes (V flow, V thromb, V ratio, and V new) between the 2 groups.

Platelets, in terms of their absolute baseline count and their decrease after the procedure, seem to be an important factor in developing PIS after EVAR. Further, more tailored studies are needed to elucidate the role of platelets and flow or thrombus volumes in the development of PIS.