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INTRODUCTION:
Type I attachment site endoleaks are the most common type of endoleak following thoracic endovascular aortic repair (TEVAR) and represent treatment failures. Although Type I endoleak rates after TEVAR are well described, little is known about endoleak rates for devices deployed with landing zones in previously placed surgical Dacron grafts. As such, the present study sought to examine Type I endoleak rates following endograft deployment within Dacron landing zones versus native aorta.
METHODS:
Retrospective analysis of a prospectively maintained IRB-approved database was performed for all patients undergoing TEVAR at a single referral institution between 5/2002 and 6/2012. N=367 patients were identified as having undergone TEVAR for the treatment of arch, descending thoracic, or thoracoabdominal aortic pathology. Of these, n=312 patients (n=330 procedures) had at least one follow up contrast-enhanced CTA to establish the presence of an endoleak. All devices were deployed with a minimum of 2-3 cm of proximal and distal seal zone in accordance with device instructions for use. Attachment site landing zones were classified as native aorta or Dacron. Type I endoleak rates were compared between native and Dacron landing zones using a chi-square test stastistical analysis. An unpaired t-test was employed for analysis of continuous data.
RESULTS:
Baseline characteristics of each group are presented in Table 1. There were a total of 596 landing zones in native aorta versus 72 in Dacron (Table 2), of which 42 were proximal and 30 were distal from past/concurrent procedures (Table 3). Type I endoleak was observed in 3.7% (22/596) of native aorta landing zones versus 2.8% (2/72) of Dacron landing zones (p=0.67). Both Dacron landing zone endoleaks were Type Ia with no Type Ib leaks. Comparison of the initial tertile of experience with Dacron landing zones (n=20 procedures, n=22 landing zones) to the latter two tertiles (n=41 procedures, n=50 landing zones) revealed evidence for a learning curve with both endoleaks in the initial experience (2/22; 9.1% versus 0/50; 0% in latter tertiles; p=0.03). Both initial tertile endoleaks were in short (2 and 2.5 cm) Dacron landing zones whereas a policy of minimum 4 cm Dacron landing zone length was utilized in the latter two tertiles.
CONCLUSIONS:
Endograft deployment within long-segment Dacron (>4 cm landing zone length) appears to reduce type I endoleak rate relative to native aorta landing zones. In cases of a borderline native aortic landing zone, a hybrid procedure to create an adequate Dacron landing zone may decrease the risk of type I endoleak.

Table 1: Pre-Operative Demographics

	Native Landing Zone	Dacron Landing Zone	p-Value
Total Patients	254	58
Total Procedures	269	61
Age (years) (IQR)	66.0 (54.0-75.0)	67.0 (55.8-74.0)	0.83
Sex (% Male)	160/269 (59%)	32/61 (52%)	0.32
Surgical Indication: Aneurysm	242	64	0.19
Surgical Indication: Dissection	95	21	0.71
Surgical Indication: Transection	19	0	0.03
Maximum Aortic Diameter (cm) (range)	5.6 (2-12)	6.7 (3.7-10.1)	<0.0001

Table 2: Landing Zones and Associated Endoleaks

	Native Landing Zone	Dacron Landing Zone	p-Value
Proximal Landing Zones	288 (48%)	42 (58%)	0.11
Distal Landing Zones	308 (52%)	30 (42%)	0.11
Total Landing Zones	596	72
Proximal Endoleak Rate (Ia)	13/288 (4.5%)	2/42 (4.7%)	0.94
Distal Endoleak Rate (Ib)	9/308 (2.9%%)	0/30 (0%)	0.34
Total Endoleak Rate	22/596 (3.7%)	2/72 (2.8%)	0.67
Median Duration of Follow Up (months) (IQR)	33.2 (14.7, 55.6)	18.8 (7.4, 38.6)	0.002

Table 3: Endograft/Dacron Implantation Procedures

Prior Open Abdominal Aortic Replacement	16/72 (22.2%)
Prior Open Descending Aortic Repair	8/72 (11.1%)
Prior Ascending +/- Hemi-Arch Replacement	11/72 (15.3%)
Prior Stage I Elephant Trunk Procedure	15/72 (20.8%)
Prior Open TAAA Repair	12/72 (16.7%)
Multiple Prior Aortic Surgeries	10/72 (13.9%)