Dr Rao Vallabhaneni, Liverpool University, UK and researchers from the University of Malmo, Sweden, have reported that giant Palmaz stents are effective in improving proximal seal and possibly fixation during endovascular repair (EVAR) by enhancing apposition and alignment between the stent-graft and the aneurysm neck. Giant Palmaz stents have been used during EVAR of infra-renal aortic aneurysms in order to correct proximal Type I endoleaks arising due to adverse anatomy with poor apposition between stent-graft and the sealing zone. The aim of this study was to evaluate the immediate efficacy and durability of Palmaz 4014 stents deployed at the proximal seal zone.
The investigators recruited 65 patients who had a primary implantation of a Palmaz stent at the proximal anastomotic zone, who were identified from a cohort of 415 who underwent EVAR over a six-year period. Follow-up data (median duration 24 months, range 1-60) was examined to identify stent-graft migration, late proximal Type I endoleak and changes in aneurysm neck in relation to the Palmaz stent. During the procedures, the Palmaz stents were always dilated at deployment to the same size as the preoperative neck diameter and the stent-grafts were oversized by 10 to 15% in relation to this diameter.
The results revealed that the Zenith stent-grafts were used in all but one patient who received a home-made device. Indication for a Palmaz stent was unsatisfactory apposition between stent-graft and the neck without endoleak in 13 patients, a proximal Type I endoleak in 51 patients and a lumbar artery reperfusion entering within the seal-zone in an additional patient. The endoleak was abolished in all but two patients without recourse to further intervention. In addition, the rupture of the aneurysm neck in one patient who died was the only complication attributed to Palmaz stent deployment.
Following cross-sectional CT imaging, the Palmaz stents were observed to be in close contact with the stent-graft in the early follow-up. During late follow-up however, Palmaz stents were noted to separate from the stent-graft in most patients with appearance of space between the Palmaz stent and the stent-graft. In addition, stent-graft migration was noted in two patients of whom one also developed severe stent-graft distortion and secondary proximal Type I endoleak.
Although associated with a small risk of rupture of aneurysm neck during deployment, the researchers concluded that the Palmaz stents can improve proximal seal and fixation during EVAR, which is achieved by enhancing apposition and alignment between the stent-graft and the aneurysm neck. However, the additional radial force provided by the Plamaz stent to achieve this is lost during follow-up, as the contact between the Palmaz stent and the stent-graft is diminished or lost.
The investigators called for additional studies into the mechanisms that cause the loss, and emphasised that longer follow-up is required to determine the potential consequences of this finding.
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