Outcomes of covered expandable stents for the treatment of TASC D aorto-iliac occlusive lesions

Study design

We performed a retrospective study of patients who underwent an endovascular procedure for aorto-iliac occlusive disease from March 2010 to September 2012. Cases were identified from both a database maintained at the Princess Alexandra Hospital and a smaller number of cases performed by the authors at the St Andrews Hospital in Queensland, Australia. All patients were either booked electively from an outpatient clinic or were admitted with critical limb ischaemia. Clinical, perioperative and demographic data were obtained through review of hospital records. Lesions were classified according to severity using the TASC II guidelines following consultant radiologist review of intra-procedural angiograms (Figure 1). All lesions classified TASC A, B or C on criteria were excluded from the study. ⁵ Clinical features of lower-limb ischaemia were classified and followed up using the Fontaine classification. ⁷ All cases utilised the Atrium Advanta V12© Balloon mounted PTFE covered stent system.

Stents and procedures

All patients were evaluated pre-procedure with Computed Tomography (CT) angiogram, Duplex ultrasound (DUS) or both. All procedures were performed in an interventional angiography suite or hybrid operating theatre. Procedures were preferentially performed percutaneously under local anaesthesia. General anaesthetic was utilised where a prolonged procedure or concomitant open approach was anticipated. Percutaneous endovascular access was obtained under ultrasound guidance either via bilateral retrograde common femoral artery punctures or a combined femoral/brachial approach under aseptic Seldinger technique. A 5Fr sheath was inserted and following guide wire access, a digital subtraction angiogram was performed via a pigtail catheter. Lesions were then crossed either endoluminally or subintimally with 5000 units of Heparin cover. Cases where lesions could not be crossed were not included in the case series. Preferentially, a Van Schie Beacon® Tip Seeking Catheter (Cook Medical Inc, Bloomington, IN, USA) was used to cross the lesion/s. This was followed by exchange to a 7Fr 45 cm long sheath. Stent length and diameter characteristics were determined based on measurements of the length of the lesion and the diameter of the adjacent normal vessel. The delivery system was positioned and balloon-expandable PTFE-covered stents were deployed. Stents were deployed simultaneously in the case of ‘kissing’ iliac stents. After deployment, stents were routinely dilated using a balloon catheter of the same size or 1 mm smaller. Post-stenting angiography was routinely performed to confirm stent and runoff patency. Technical success was defined as successful vascular access and completion of the endovascular procedure, as well as <30% residual diameter reduction on completion angiography. ⁸ Occasionally, self-expanding stents were used for residual disease of the external iliac arteries. Manual pressure or a closure device was used in cases of percutaneous access. Protamine was occasionally given at the discretion of the surgeon.

Medical therapy

All patients were placed on pre- and post-operative antiplatelet therapy. All cases were performed with broad-spectrum antibiotic cover given at induction of anaesthesia. Single antiplatelet therapy was continued indefinitely post-stenting. All patients were placed on an HMGCoA reductase inhibitor.

Study end points

Our primary endpoint was primary patency, which was defined as uninterrupted patency without further procedures performed on, or at the margins of the treated segment at the end of follow-up. Secondary endpoints were secondary patency, technical success, complications, limb salvage and survival. Secondary patency was defined as a patent-treated segment following further intervention to maintain patency. Restenosis was defined as a greater than 2.5 peak systolic velocity index on colour DUS or greater than 30% diameter reduction in a treated segment on angiography. ⁸ Follow-up of stent patency was based on clinical and radiological assessments. ABI measurements were not routinely recorded. Patients were routinely followed up with aorto-iliac DUS performed at 6 weeks, 6 months and 12 months after intervention. Surveillance DUS studies were sought annually thereafter.

Statistical analysis

To measure the primary/secondary patency rates for the patient group, Kaplan–Meier estimators were used to estimate the survival function over time. For univariate comparisons of the pre-operative factors, log-rank tests were performed to evaluate whether differences in survival functions existed between groups. Both Kaplan–Meier and univariate analysis were performed with Graphpad Prism software (Version 5 for Mac, Graphpad software, San Diego, CA, USA). Differences were considered statistically significant for P < 0.05.

Demographic data

Demographic data are summarised in Table 1. During the study period, 30 patients had covered stents inserted for aorto-iliac occlusive disease. The median age was 67 years (range 48–84) and the male to female ratio was 1:3.6. All of the patients were symptomatic, with either claudication (Fontaine stage 2), rest pain (Fontaine stage 3) or tissue loss (Fontaine stage 4). Twenty-nine of the patients were current or ex-smokers (97%), 13 suffered from diabetes mellitus (43%), 22 had hypercholesterolemia (73%), 24 had hypertension (80%), 13 had a history of ischaemic heart disease (43%) and three patients had chronic renal failure (10%). One patient was known to suffer from a hypercoagulable state (3%).

OPEN IN VIEWER

Table 1.

Baseline characteristics.

Variable	No. (% or range)
Number of patients	30
Median age	67 (48–84)
Male	8 (26.6)
Fontaine Classification
Stage I	0
Stage II	13 (43.3)
Stage III	16 (53.3)
Stage IV	1 (3.3)
Risk Factors
Diabetes	13 (43.3)
Hypertension	24 (80)
Smoking	29 (96.6)
Chronic kidney disease	3 (10)
IHD	13 (43.3)
Hypercholesterolaemia	22 (73.3)
Hypercoagulable state	1 (3.3)

Pre-procedural imaging

Disease was evaluated pre-intervention with CT angiography in 19 cases, DUS alone in six patients and a further five patients underwent both imaging modalities. Procedural details are summarised in Table 2. Six patients had disease isolated to the infrarenal aorta (Figure 2) whilst 18 patients had both aortic and iliac involvement. Overall, there were 19 complete occlusions and 11 stenotic lesions treated. There were six isolated aortic occlusions (20%) and 13 aorto-iliac occlusions (43%). The remaining 11 patients had diffuse stenotic disease extending from the aorta to the iliac arteries (37%). All patients were classified as TASC D according to criteria.

OPEN IN VIEWER

Table 2.

Procedural details.

Variable	No. (%)
Radiological disease
Aortic occlusion/stenosis	6 (20)
Aortoiliac occlusion/stenosis	24 (80)
Approach
Retrograde – CFA only	21 (70)
Combined – CFA + L Brachial	9 (30)
Anaesthetic
Local	18 (60)
GA	12 (40)
Radiological success
<30% residual	30 (100)
Complications
Haematoma	1 (3.3)
Distal embolisation	1 (3.3)

Procedure

Eighteen patients were treated via local anaesthetic to the puncture site, whilst 12 patients required general anaesthesia. There were three cases of an open approach to the common femoral artery, two of which involved concomitant common femoral endarterectomy. Technical success was achieved in 100% of the cases treated. Stent configuration comprised ‘kissing’ iliac stents in 20 patients, a large diameter aortic stent with iliac stenting in six patients, and an aortic stent alone (Figure 3) in four patients. Two procedural complications were reported amongst the cohort. There was one case of in-stent thrombosis that required thrombectomy with distal emboli to the internal iliac artery. This was attributed to a failure to give heparin prior to deployment of the stent. Localised rectal ischaemia was found on colonoscopy following the procedure, although this was managed conservatively. One significant groin hematoma was also reported and this too was managed conservatively. There were no vessel wall ruptures or dissections. No planned percutaneous cases required conversion to an open approach.

Follow-up

The average follow-up was 14.23 months (range 4-38 months) with a reported median of 13 months. The median Fontaine classification improved from three pre-stent placement to two post-stenting. An open distal revascularisation procedure was performed following AIS in four cases. As mentioned, two patients underwent concomitant common femoral endarterectomy. A single patient underwent a planned femoro-femoral crossover graft procedure after aortic and uni-iliac stenting. Another patient proceeded to femero-popliteal bypass graft. Both were performed as separate procedures. The median length of stay was two days. Four patients stayed in hospital for longer than seven days requiring multiple other surgical procedures. Eight patients were discharged on day 1 post-endovascular intervention.

Primary patency at 6, 12 and 24 months was 97%, 90% and 79%, respectively (Figure 4). There was no statistically significant difference in primary patency for patients stratified by Fontaine staging. Four of the iliac stents developed stenoses within the follow-up period whilst all the aortic stents remained patent on DUS. Four patients failed to attend for follow-up DUS and were lost to follow up after six-week clinic review. All these patients had a 1-point reduction in Fontaine classification post-stenting. Secondary patency was successfully achieved in three cases; one with repeat stenting and the other two with balloon angioplasty for in-stent stenosis. No complications were reported for re-interventions. Secondary patency could not be achieved in a single case as the patient elected for conservative management. Subsequently, secondary patency was 97% at the end of follow-up for a limb salvage rate of 100% (Figure 4). OPEN IN VIEWER

OPEN IN VIEWER

Figure 3.

A post-procedural digital subtraction angiogram demonstrating successful treatment with a single covered Aortic stent.

OPEN IN VIEWER

Figure 4.

Kaplan–Meier survival curve estimates for primary and secondary patency in all patients treated for aorto-iliac occlusive disease.

One patient death was recorded within the follow-up period following discharge from hospital 4.5 months post-intervention. The patients’ last DUS at four months confirmed primary stent patency. The certified cause of death was congestive cardiac failure on a background of renal failure and ischaemic heart disease.

Conclusion

Our case series demonstrates that treatment of complex aorto-iliac occlusive disease with covered balloon-expandable stents can have acceptable results with good patency and good clinical outcome. In cases of re-stenosis, secondary patency can often be achieved with repeat stenting with rates comparable to open surgical revascularisation, and carrying a much lower morbidity rate than an open procedure. Larger studies, with longer follow up periods, are required to confirm acceptable long-term patency rates compared with open surgical intervention in patients with radiologically severe disease. Furthermore, cost analysis of an endovascular approach, with its anticipated high re-intervention rate, would aid vascular surgeons in future treatment decisions.