Current evidence regarding chimney graft occlusions in the endovascular treatment of pararenal aortic pathologies: a systematic review with pooled data analysis.

PURPOSE: To review the literature on pararenal endovascular aneurysm repair (EVAR) to determine the frequency and clinical relevance of chimney graft occlusions. METHODS: A comprehensive search of the English-language literature abstracted in the Medline and the Cochrane Library databases was performed to identify case series involving pararenal aortic pathologies (degenerative aneurysms, penetrating atherosclerotic ulcers, type Ia endoleaks, and para-anastomotic aneurysms) treated with EVAR and chimney grafts; thoracoabdominal, iliac, or aortic arch chimney graft placements were excluded, as were case reports in which the total number of chimney grafts implanted at the reporting center could not be determined. The literature search identified 83 studies regarding chimneys/snorkels for pararenal pathologies published between January 2007 and March 2014. Of these, 7 studies met the inclusion criteria and were included in the analysis. RESULTS: There were 15 (4.5%) occlusions in the overall 334 renovisceral vessels in which chimney grafts were deployed. The mean time to chimney graft occlusion was 3.5 months (range 1-270 days) over a mean follow-up of 1.4 months (range 9-24). The target arteries were the renal artery (n=12) and the superior mesenteric artery (SMA; n=3). Seven patients were asymptomatic, and no description was given in 5 cases. In the other 3 patients, the symptoms were acute renal failure, intestinal ischemia, and malignant hypertension. The treatment strategy included open conversion and iliorenal bypass (n=1), exploratory laparotomy to revascularize the SMA (n=1), hemodialysis (n=1), placement of bare metal stents (n=4), conservative treatment (n=2), and unknown (n=6). One (6.7%) patient died (an occluded SMA). Two patients with renal chimney occlusion suffered from temporary renal function deterioration. CONCLUSION: The present analysis identified a low rate of chimney graft occlusions, which appear to occur generally a few months after placement. Involvement of the renal artery had no severe clinical consequences, while occlusion of the SMA can be associated with life-threatening complications. More detailed information regarding occluded chimney grafts will be needed in future publications to help identify the causes.