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Original Contribution
Twelve-Month Results of Percutaneous Endovascular Reconstruction for Chronically Occluded Superficial Femoral Arteries: A Qualit
July 2006
Atherosclerotic peripheral vascular disease (PVD) is an underdiagnosed, undertreated, age-dependent, debilitating condition. Conservative estimates suggest that between 8 and 12 million people in the United States have PVD.1 The incidence of intermittent claudication (IC) increases with age,2 and the prevalence varies from 0.4% to 14% of the adult population.3 Furthermore, the prevalence of asymptomatic disease is greater than 25% in select populations, particularly the elderly.4,5 Moreover, it is often underappreciated that the presence of PVD is a powerful and independent predictor of mortality.6,7
Compared to patients without PVD, patients with PVD ambulate at a slower pace and shorter distances in order to avoid ischemic leg pain, thereby leading to tremendous limitations in personal, social and occupational activities. Ultimately, patients with severe advanced PVD and IC become housebound and experience a marked negative impact on perceived quality of life (QOL). Validated QOL assessment tools, such as the SF-35 questionnaire, demonstrate that patients with PVD have impairment in QOL worse than that of patients with severe migraine headaches, and similar to patients with New York Heart Association Class III congestive heart failure.8
The Trans-Atlantic Inter-Society Consensus (TASC) statement is a comprehensive position paper on the diagnosis and treatment of acute and chronic PVD published as an accord of several North American and European vascular societies. The TASC statement categorizes atherosclerotic disease of the superficial femoral artery (SFA) into 4 distinct classes. The recommended revascularization strategy for chronic total occlusions (CTO), or TASC D lesions, is bypass surgery.9
We hypothesized that percutaneous endovascular reconstruction of SFA CTOs (i.e., “surgical disease”) using standard angioplasty techniques with primary nitinol stent placement can be performed with a high degree of acute procedural technical success, be as clinically durable as surgical revascularization and can significantly improve patient QOL.
We report our procedural results and clinical follow up from our peripheral database on endovascular therapy for SFA TASC D lesions.
Methods
We reviewed our database for patients who underwent attempted percutaneous revascularization for SFA CTO at Genesis Medical Center in Davenport, Iowa. Traditional angioplasty and primary stenting techniques were employed utilizing the nitinol SMART® stent (Cordis Corp., Miami, Florida). The stent diameter was oversized by 1–2 mm greater than the target reference vessel lumen, and post-dilatation was performed with a balloon diameter equal to the reference vessel lumen by visual estimate. High-pressure inflations were avoided. The stent length maximized coverage of the diseased segment; “spot” stenting was avoided. Periprocedural antithrombin therapy included either unfractionated heparin, enoxaparin or bivalirudin, while glycoprotein IIb/IIIa inhibitor use with either abciximab or eptifibatide was at the discretion of the individual physician.
All patients were treated with aspirin 81–325 mg and clopidogrel 75 mg once per day post-stent implantation for a minimum of 30 days. They were all counseled on risk factor modification, encouraged to participate in regular walking programs and refrain from tobacco use. The patients were treated with appropriate pharmacotherapy to lower cholesterol, blood pressure and control diabetes, as indicated by national guidelines. Angiographic variables were obtained by a single, independent observer using standard caliper measurements.
The Walking Impairment Questionnaire (WIQ – Appendix),10 is a QOL questionnaire that was specifically designed to assess the degree of impairment experienced by patients with claudication. Question 1 is divided into two parts: the first is to assess the degree of difficultly walking that is specific to claudication, and the second is a differential diagnosis of other etiologies that would limit ambulation, such as orthopedic or neurologic problems. Question 2 measures the difficultly walking a given distance on level ground, Question 3 measures the ability to walk at various speeds for 1 block, and Question 4 measures the degree of difficulty climbing stairs without stopping.
Clinical outcomes were assessed by asking patients to complete Question 2 of the WIQ (score range: 0 to 14,080) pre-intervention, and then systematically every 3 months for the first year, then every 6 months thereafter. A patient with a total score of 0 on Question 2 would not be able to walk indoors around his/her home without claudication, while a maximum score of 14,080 would be achieved by a patient who can walk 5 blocks (1,500 feet) without claudication.
Objective assessment of vessel patency was obtained through serial ankle-brachial index (ABI) measurements obtained pre-intervention, immediately post-intervention, every 3 months for the first year, then every 6 months thereafter. Categorical demographic and procedural variables were summarized as frequencies and percentages. Continuous variables were summarized as means ± standard deviation. Statistical analysis was performed on continuous variables pre- and post-intervention using the Wilcoxon Signed Rank test. P-values were considered statistically significant at Results
A total of 44 consecutive patients (51 legs) underwent attempted percutaneous revascularization for SFA CTO TASC Type D lesions. Successful revascularization with angioplasty, stent deployment and restoration of normal vessel patency was achieved in 90.2% of the cases, with a mean follow-up of 374 ± 321 days. Figure 1A depicts an example of a TASC D lesion pre-endovascular intervention, and Figure 1B demonstrates the angiographic result post-intervention. The single cause of failure in 9.8% of the cases was inability to cross the occlusion and obtain distal intraluminal position with a wire. Baseline patient characteristics are listed in Table 1. The procedural details and lesion characteristics are listed in Table 2. All lesions were TASC D lesions. The mean minimum stent diameter averaged 1.1 mm greater than the mean maximum balloon diameter, consistent with the technique of oversizing the stents, as described above.
The clinical outcomes and ABI measurements are listed in Table 3, with individual patient data depicted in Figures 2 and 3. The mean pre-WIQ score was 722 ± 1,503, and the mean post-WIQ score was 8,421 ± 5,741 (p Discussion
The widespread acceptance of stenting SFA CTOs has been hampered by early poor results. This paper describes a high technical success rate, low periprocedural complication rate, and favorable clinical follow up at 12 months using standard percutaneous techniques to revascularize chronically occluded SFAs.
One hurdle in assessing the efficacy of peripheral endovascular therapy is the numerous endpoints that can be measured and the lack of consistent reporting. For example, the coronary literature typically uses the standard triple endpoints of death, myocardial infarction (MI) and repeat revascularization. However, death and MI are rare events and are not clinically appropriate endpoints in the endovascular intervention. In contrast, the peripheral literature has used limb salvage, time-to-claudication, distance-to-claudication, maximal walking distance, serial ABIs, serial duplex Doppler studies, angiographic binary restenosis and revascularization rates as study endpoints. Arguably, the most important clinical endpoint is the patient’s sense of wellbeing and overall quality of life.
The WIQ is a validated, standardized questionnaire that directly measures QOL and was specifically designed to measure response to therapy for peripheral vascular disease. The data from this study demonstrate a very significant improvement in patient QOL after percutaneous endovascular intervention for “surgical disease”. Furthermore, the significant magnitude and persistence in improvement of the ABIs demonstrate an objective sustained benefit to stenting SFA CTOs with nitinol SMART stents.
Stenting is clearly superior to balloon angioplasty alone in reducing early and late target vessel revascularization rates in the coronary circulation,11,12 particularly for chronic occlusions.13,14 Balloon angioplasty has a high failure rate in the SFA territory.15 A logical extrapolation is that stenting the SFA, particularly CTOs, should lead to improved outcomes. Peripheral self-expanding stents were initially introduced in the early 1990s, and offered optimism due to the success seen in the coronary literature. However, this enthusiasm was not supported in clinical practice nor the peripheral literature,16,17 and stenting the SFA typically remains reserved for failed percutaneous transluminal angioplasty.
While early data with the Wallstent (Boston Scientific Corp., Natick, Massachusetts) has had unfavorable results, but this has not been the case with the nitinol SMART stent, introduced in the late 1990s.18 Nitinol is a nickel-titanium alloy with thermal memory properties that provide the stent with self-expanding characteristics. In fact, the bare-metal stent arm of the Sirolimus-eluting Stents for the Treatment of Obstructive Superficial Femoral Artery Disease (SIROCCO) study demonstrated a surprisingly low angiographic binary restenosis rate of 17.6% at 6-month follow up.19 However, concerns regarding stent fracture, combined with a lack of understanding of the complex, tortuous, dynamic anatomy of the SFA, have delayed the widespread acceptance of stenting infrainguinal vessels.
Endovascular therapy with conventional angioplasty and nitinol stenting offers attractive advantages to surgery. A minimally invasive percutaneous approach is lower in morbidity and mortality, is less painful and has a shorter recovery time than surgical revascularization. Furthermore, traditional femoral-popliteal bypass is not a panacea, and typically averages primary 2-year patency rates of approximately 69–81%, and 5-year patency rates of approximately 39–73%.20,21 However, until recently, there have been little data that would support the widespread endovascular approach to revascularizing SFA CTOs.
Study limitations. This study represents a small, nonrandomized patient population at a single center. Clearly, more data are necessary from larger, randomized studies in order to make any conclusive recommendations or change the currently accepted guidelines.
Since this is a single-arm, prospective series with no comparative arm, there certainly could be the introduction of a treatment bias from simply having undergone a procedure. Arguably, though, there was a parallel improvement in the ABI, which is an objective measure of distal perfusion. This suggests that the subjective improvement in QOL is not biased by a “procedure/placebo” effect.
Collectively, this cohort had an overall improvement in their WIQ score and ABI. However, individually, there were patients who had a greater magnitude of benefit than others. Not all patients experienced an improvement in their WIQ score, which is probably explained by confounding coexisting conditions that limit ambulation such as orthopedic and neurologic disorders. In addition, not all ABIs were improved at follow up, which is probably due to in-stent restenosis and/or significant residual disease, for example, in the infratrifurcation vessels.
While 12-month follow up is rather standard in the cardiology literature, typical vascular surgery literature describes 3- to 5-year follow up as standard. Currently, the long-term primary and secondary patency rates for peripheral vascular stenting with nitinol stents are unknown. Stent fractures could be a major factor in long-term follow up. New stent designs will have to incorporate a better understanding of the complex torsional, axial and compressive forces placed on these devices.
Finally, as mentioned above, lack of consistent standardized endpoints makes it impossible to pool small series such as this and perform a meta-analysis of similar data sets. An agreed-upon standardized endpoint should be adopted for future studies.
Conclusions
Surgical revascularization for Type D lesions has typically been reserved for limb-threatening or resting pain situations, thereby undertreating patients with claudication alone. These data demonstrate that endovascular reconstruction of Type D lesions for claudication can be performed safely with a marked improvement in quality of life and without an increased risk of amputation at 12 months. Endovascular therapy has already gained widespread acceptance as a first-line approach for TASC Type A–C lesions. These data suggest the spectrum could be extended to Type D lesions.
This study confirms that long, complex, chronically occluded SFAs can be revascularized with a very high technical success rate utilizing a percutaneous approach. Furthermore, the technical success rate will only increase with the development of new devices to cross total occlusions.
Patients with claudication experience a dramatic improvement in their quality of life and sense of wellbeing following percutaneous endovascular reconstruction of SFA CTOs. The qualitative improvement is reinforced by the objective improvement of the ABI. The low target vessel revascularization rate at 12 month is consistent with other data on the SMART stent and confirms the durability of the procedure.
Due to the low morbidity and mortality rates and minimal invasiveness of endovascular therapy, a percutaneous approach could be considered as a first-line treatment strategy for PVD revascularization, regardless of the lesion classification. Regardless of the revascularization strategy employed, aggressive medical therapy and risk factor modification is mandatory to reduce long-term morbidity and mortality rates for systemic atherosclerosis.
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