Expert Review of Cardiovascular Therapy Downloaded from informahealthcare.com by Nyu Medical Center on 07/06/15 For personal use only.
Review
Recent advances in self-expanding stents for use in the superficial femoral and popliteal arteries Expert Rev. Cardiovasc. Ther. 12(7), 833–842 (2014)
Arash Aghel and Ehrin J Armstrong* Division of Cardiology, University of Colorado School of Medicine, 1055 Clermont Street, Denver, CO, USA *Author for correspondence: Tel.: +1 415 312 2480 Fax: +1 415 655 1206 [email protected]
Significant advances have been made in femoropopliteal stent design and clinical outcomes during the past decade. Initial randomized studies demonstrated superiority of nitinol self-expanding stents to balloon angioplasty for treatment of moderate-length superficial femoral artery stenoses. During longer-term follow-up, first generation nitinol stents were hampered by high rates of stent fracture. A number of newer nitinol stent designs have been developed with improved conformability, greater radial strength and lower rates of long-term stent fracture. These newer stent designs have demonstrated superior primary patency and decreased restenosis for the treatment of moderate-length femoropopliteal lesions relative to historical benchmarks. Recent advances in drug-eluting nitinol stents have also offered treatment options for challenging lesion subsets including very long femoropopliteal lesions and for the treatment of in-stent restenosis. This article reviews recent advances and upcoming research in nitinol self-expanding stent technology for the treatment of superficial femoral and popliteal artery stenosis. KEYWORDS: claudication • nitinol stents • peripheral artery disease • popliteal artery • randomized trials • restenosis • stent • superficial femoral artery
Peripheral arterial disease (PAD) affects an increasing number of patients worldwide, with an age-adjusted prevalence ranging from 12 to 20% [1–3]. While medical therapy is paramount for all patients with PAD [4,5], patients with lifestyle-limiting claudication or nonhealing arterial wounds often require intervention. Atherosclerotic diseases of the superficial femoral arteries (SFA) and popliteal arteries are common anatomic culprits in such patients. A number of endovascular options are available for treatment of femoropopliteal disease, but stenting has become increasingly common as stent patency improves and newer generations of stents are able to withstand the mechanics of knee and thigh flexion and torsion [6]. This article reviews recent advances and upcoming research in nitinol self-expanding (SE) stent technology for the treatment of superficial femoral and popliteal artery stenosis, with a focus on recent clinical trials and registries of newer generation stents.
informahealthcare.com
10.1586/14779072.2014.918505
Randomized trials of nitinol stents
Six major studies have compared nitinol stents to balloon angioplasty: the INTRACOIL study, the Vienna Absolute study, the Femoral Artery Stent Trial (FAST), the ASTRON trial, the SUPER trial and the RESILIENT trial (TABLE 1). These trials form the basis for current performance benchmarks when assessing other nonrandomized studies of newer stent designs [7]. The INTRACOIL study was the first major randomized trial of a nitinol stent versus balloon angioplasty. The Intracoil stent (eV3, Inc., Plymouth, MN, USA) has a coiled design that allows for increased flexibility in the SFA segment. In a randomized multicenter study of the Intracoil stent versus balloon angioplasty that included 266 patients randomized 2:1 to stent versus angioplasty, there was no difference in 9-month rates of repeat revascularization (14.3 vs 16.1%) [8]. The randomized study is not published, but data from
2014 Informa UK Ltd
ISSN 1477-9072
833
Review
Aghel & Armstrong
Expert Review of Cardiovascular Therapy Downloaded from informahealthcare.com by Nyu Medical Center on 07/06/15 For personal use only.
Table 1. Randomized trials of nitinol stents versus balloon angioplasty in the superficial femoral artery. Study
Stent type
Patients (n)
Lesion length
CTO (%)
Calcified† (%)
Primary patency, 1y
TLR, 1 y
PSVR definition
Stent fracture, 1y
INTRACOIL
Intracoil
135 stent 131 PTA
36 mm stent 33 mm PTA
23% stent 17% PTA
NR
NR
14% stent‡ 16% PTA‡
NR
NR
Vienna Absolute
Dynalink or Absolute
51 stent 53 PTA
101 mm stent 92 mm PTA
37% stent 32% PTA
80% stent 85% PTA
63% stent 37% PTA
37% stent§ 54% PTA§
‡2.4
2%
FAST
Luminexx3
123 stent 121 PTA
45 mm stent 44 mm PTA
36% stent 24% PTA
48% stent 44% PTA
68% stent 61% PTA
14% stent 18% PTA
‡2.4
12%
ASTRON
Astron
34 stent 39 PTA
82 mm stent 65 mm PTA
38% stent 39% PTA
NR
66% stent 39% PTA
NR
‡2.4
NR
SUPER
SMART
74 stent 76 PTA
123 mm stent 177 mm PTA
96% stent 91% PTA
57% stent 47% PTA
46% stent 43% PTA
13% stent 21% PTA
‡2.5
NR
RESILIENT
Lifestent
134 stent 72 PTA
70 mm stent 64 mm PTA
17% stent 18% PTA
35% stent 34% PTA
81% stent 37% PTA
13% stent 55% PTA
‡2.5
3%
†
Percent calcified lesions are reported for lesions with moderate or greater calcification. Value at 9 months of follow-up. Value at 2 years of follow-up. CTO: Chronic total occlusion; NR: Not reported; PSVR: Peak systolic velocity ratio; PTA: Percutaneous transluminal angioplasty; TLR: Target lesion revascularization. ‡ §
the roll-in portion of the study suggested excellent acute results; a separate two-center study reported primary patency rates at 12 months of 86% for treatment of short lesions [9,10]. While the Intracoil stent is FDA approved for use in the SFA, it is rarely used due to difficulty in accurate deployment, short available stent lengths and improved patency with newer iterations of nitinol SE stents. The Vienna Absolute Study randomized patients 1:1 to a 6-mm Dynalink or Absolute stent (Abbott Vascular, Santa Clara, CA, USA) versus balloon angioplasty of the SFA [11]. One hundred and four patients were enrolled with an average lesion length of 101 mm in the stent group and 92 mm in the balloon angioplasty group. The average length of the treated segment was 132 mm in the stent group and 127 mm in the angioplasty group. One-third of patients had a total occlusion of the SFA, and two-third of lesions were characterized as having moderate–severe calcification. About 57% of the patients had one stent implanted and 27% had two stents implanted. Of note, there was a 32% crossover rate from balloon angioplasty to stenting due to suboptimal results (>30% residual stenosis or flowlimiting dissection). Restenosis rates at 1 year based on duplex ultrasound peak systolic velocity ratio (PSVR) ‡2.4 favored stenting over angioplasty (37 vs 63%; p = 0.01). There was also a statistically significant difference in walking time and ankle brachial index (ABI) in favor of stenting at 12 months, and the lower rates of restenosis with stenting were sustained to 2 years [12]. Two-year follow-up also showed a trend toward decreased rates of target lesion revascularization (TLR) (37 vs 54%) with primary stenting. These early results suggested that nitinol SE stents are superior to balloon angioplasty for moderate length (80–150 mm) femoropopliteal lesions. 834
The FAST randomized patients 1:1 to placement of a Luminexx3 stent (Bard Inc., Tempe, AZ, USA) versus balloon angioplasty for shorter SFA lesions [13]. The mean lesion length for both groups was 45 mm, with 36% of the stented group having total occlusions compared with only 24% with occlusions in the balloon angioplasty group (p = 0.05). More than 50% of the patients were characterized as having none–mild calcification. Binary restenosis at 12 months PSVR ‡2.4 by duplex ultrasound was 38% in the balloon angioplasty (percutaneous transluminal angioplasty [PTA]) group and 31% in the stent group by intention-to-treat (ITT) analysis (p = 0.37). TLR at 12 months was also similar between the two groups (18% PTA and 14% stent; p = 0.5). The higher prevalence of total occlusions in the stenting arm, shorter lesion length compared with other studies and small sample size may have contributed to the equivalent rates of restenosis between the two treatment modalities. The ASTRON trial randomized patients 1:1 to the Astron stent (Biotronik GmbH, Berlin, Germany) versus balloon angioplasty in a total of 73 patients with mean lesion length of 82 mm in the stent group and 65 mm in the angioplasty group (p = 0.02) [14]. The average length of the treated segments was 98 and 71 mm in the stent and PTA groups (p = 0.01), respectively. More than one-third of the lesions were total occlusions. Fifty percent of the patients received one stent only and less than 10% had more than two stents placed. By ultrasound, the restenosis rates (based on a PSVR ‡2.4) in the stent and PTA groups at 12 months were 34% versus 61%, respectively (p = 0.02). The stent group also had a statistically significant increase in walking capacity compared with the PTA group. Expert Rev. Cardiovasc. Ther. 12(7), (2014)
Expert Review of Cardiovascular Therapy Downloaded from informahealthcare.com by Nyu Medical Center on 07/06/15 For personal use only.
Recent advances in SE stents for use in the superficial femoral & popliteal arteries
The SUPER trial was a multicenter UK-based randomized study of the SMART stent (Cordis, Warren, MA, USA) versus balloon angioplasty for the treatment of femoropopliteal lesions [15]. One hundred and fifty patients were randomized 1:1, and the mean lesion length was 123 mm in the stent group and 117 mm in the balloon angioplasty group. In addition to longer lesion lengths, the study had a very high prevalence of chronic occlusions (93.3%). At 12 months, primary patency (based on duplex ultrasound PSVR of ‡2.5) was 47.2% in the stent group versus 43.5% in the balloon angioplasty group (p = 0.7). Overall, these results showed no additional benefit of primary stenting compared with balloon angioplasty. Possible reasons for this include the poor overall primary patency as well as the high prevalence of chronic occlusions and subintimal angioplasty. In comparison, more recent stent designs have demonstrated significantly higher patency even in long lesions, suggesting that the results of the SUPER trial may not be generalizable to newer stent types that may have better patency with longer lesions. The RESILIENT study was a large multicenter randomized trial comparing the Lifestent (Bard Inc., Tempe, AZ, USA) to balloon angioplasty in the SFA and proximal popliteal artery [16]. Two hundred and six patients were randomized in a 2:1 fashion to stent versus balloon angioplasty. The average lesion length was 70 mm in the stent group and 64 mm in the PTA group. The percentage of total occlusions was low compared with previous studies (17–18%), and greater than 60% of lesions were characterized as having none–mild calcification. Forty percent of the patients in the PTA arm crossed over and had a stent placed due to suboptimal PTA result. The primary endpoint of the study was TLR at 12 months. Of note, patients in the PTA arm that received bailout stenting for flowlimiting dissection or suboptimal result were classified as a TLR in the ITT analysis. This caused the primary patency endpoint (restenosis based on a PSVR ‡2.5) in the ITT analysis to heavily favor stenting over PTA at 1-year follow-up (81 vs 36%; p < 0.0001). In the as-treated group, despite having longer lesions in the stent group (63 vs 47 mm; p < 0.01), primary patency was also significantly higher at 12 months (80 vs 61%; p = 0.03) [16]. However, overall freedom from TLR at 12 months was not statistically different for the two modalities based on the as-treated analysis (86 vs 75%; p = 0.15). At 3-year follow-up, freedom from TLR was significantly improved in patients randomized to stent placement based on the ITT group (75.5 vs 41.8%; p < 0.001) but was not significantly different when comparing the as-treated group (75.5% for stenting vs 70.1% for balloon angioplasty with provisional stenting) [17]. In summary, the majority of randomized studies supported the superiority of nitinol stents for moderate to long lesions of the SFA using currently available technologies. For lesions in the range of 40 mm, a strategy of stand-alone balloon angioplasty is reasonable, given the results of the FAST trial. For lesions exceeding 80 mm, current studies support a strategy of primary stenting based on duplex restenosis, while recognizing informahealthcare.com
Review
that not all cases of restenosis require reintervention. For lesions exceeding 150 mm, even a reasonable acute balloon angioplasty result is associated with high rates of subsequent restenosis, and primary stenting may be the preferred modality [18]. These issues of outcomes with longer lesion lengths have been addressed in some recent registry studies and the VIASTAR trial (see below). Registry studies of nitinol stents
A number of studies have reported registry results of newer generation nitinol stents in both the SFA and proximal popliteal artery (TABLE 2). In general, these studies have shown incremental improvement in primary patency for treatment of moderate length SFA and proximal popliteal artery lesions. Importantly, most of these studies have also included core lab adjudicated x-rays that demonstrated significantly lower rates or in some cases, no stent fractures with newer stent designs. This improved conformability and resistance to fracture may in some cases account for the improved rates of long-term primary patency with newer generation stents. One limitation of these registries is the lack of a comparator group with balloon angioplasty alone although the presence of core laboratory adjudication and dedicated duplex follow-up for most of these studies has provided important data regarding the long-term results of stent placement. Everflex stent
The Everflex stent (Covidien, Mansfield, MA, USA) is a newer generation nitinol stent with spiral connections between nitinol-linking segments, which increase conformability of the stent compared with earlier generation stents. The DURABILITY I and DURABILITY II registries have provided encouraging results with this stent for the treatment of both moderate length (DURABILITY I) and long (DURABILITY II) lesions. The Durability I trial was a multicenter study of the EverFlex stent in SFA lesions [19]. This study enrolled 151 patients with symptomatic PAD ranging from Rutherford categories 2–5. The mean lesion length was 96 mm, and 40% of the lesions were total occlusions. More than half of the lesions had no significant calcification. The study was designed to use only one stent, with a maximum available stent length of 150 mm. The primary endpoint of the study was freedom from restenosis (based on a PSVR
Review
Recent advances in self-expanding stents for use in the superficial femoral and popliteal arteries Expert Rev. Cardiovasc. Ther. 12(7), 833–842 (2014)
Arash Aghel and Ehrin J Armstrong* Division of Cardiology, University of Colorado School of Medicine, 1055 Clermont Street, Denver, CO, USA *Author for correspondence: Tel.: +1 415 312 2480 Fax: +1 415 655 1206 [email protected]
Significant advances have been made in femoropopliteal stent design and clinical outcomes during the past decade. Initial randomized studies demonstrated superiority of nitinol self-expanding stents to balloon angioplasty for treatment of moderate-length superficial femoral artery stenoses. During longer-term follow-up, first generation nitinol stents were hampered by high rates of stent fracture. A number of newer nitinol stent designs have been developed with improved conformability, greater radial strength and lower rates of long-term stent fracture. These newer stent designs have demonstrated superior primary patency and decreased restenosis for the treatment of moderate-length femoropopliteal lesions relative to historical benchmarks. Recent advances in drug-eluting nitinol stents have also offered treatment options for challenging lesion subsets including very long femoropopliteal lesions and for the treatment of in-stent restenosis. This article reviews recent advances and upcoming research in nitinol self-expanding stent technology for the treatment of superficial femoral and popliteal artery stenosis. KEYWORDS: claudication • nitinol stents • peripheral artery disease • popliteal artery • randomized trials • restenosis • stent • superficial femoral artery
Peripheral arterial disease (PAD) affects an increasing number of patients worldwide, with an age-adjusted prevalence ranging from 12 to 20% [1–3]. While medical therapy is paramount for all patients with PAD [4,5], patients with lifestyle-limiting claudication or nonhealing arterial wounds often require intervention. Atherosclerotic diseases of the superficial femoral arteries (SFA) and popliteal arteries are common anatomic culprits in such patients. A number of endovascular options are available for treatment of femoropopliteal disease, but stenting has become increasingly common as stent patency improves and newer generations of stents are able to withstand the mechanics of knee and thigh flexion and torsion [6]. This article reviews recent advances and upcoming research in nitinol self-expanding (SE) stent technology for the treatment of superficial femoral and popliteal artery stenosis, with a focus on recent clinical trials and registries of newer generation stents.
informahealthcare.com
10.1586/14779072.2014.918505
Randomized trials of nitinol stents
Six major studies have compared nitinol stents to balloon angioplasty: the INTRACOIL study, the Vienna Absolute study, the Femoral Artery Stent Trial (FAST), the ASTRON trial, the SUPER trial and the RESILIENT trial (TABLE 1). These trials form the basis for current performance benchmarks when assessing other nonrandomized studies of newer stent designs [7]. The INTRACOIL study was the first major randomized trial of a nitinol stent versus balloon angioplasty. The Intracoil stent (eV3, Inc., Plymouth, MN, USA) has a coiled design that allows for increased flexibility in the SFA segment. In a randomized multicenter study of the Intracoil stent versus balloon angioplasty that included 266 patients randomized 2:1 to stent versus angioplasty, there was no difference in 9-month rates of repeat revascularization (14.3 vs 16.1%) [8]. The randomized study is not published, but data from
2014 Informa UK Ltd
ISSN 1477-9072
833
Review
Aghel & Armstrong
Expert Review of Cardiovascular Therapy Downloaded from informahealthcare.com by Nyu Medical Center on 07/06/15 For personal use only.
Table 1. Randomized trials of nitinol stents versus balloon angioplasty in the superficial femoral artery. Study
Stent type
Patients (n)
Lesion length
CTO (%)
Calcified† (%)
Primary patency, 1y
TLR, 1 y
PSVR definition
Stent fracture, 1y
INTRACOIL
Intracoil
135 stent 131 PTA
36 mm stent 33 mm PTA
23% stent 17% PTA
NR
NR
14% stent‡ 16% PTA‡
NR
NR
Vienna Absolute
Dynalink or Absolute
51 stent 53 PTA
101 mm stent 92 mm PTA
37% stent 32% PTA
80% stent 85% PTA
63% stent 37% PTA
37% stent§ 54% PTA§
‡2.4
2%
FAST
Luminexx3
123 stent 121 PTA
45 mm stent 44 mm PTA
36% stent 24% PTA
48% stent 44% PTA
68% stent 61% PTA
14% stent 18% PTA
‡2.4
12%
ASTRON
Astron
34 stent 39 PTA
82 mm stent 65 mm PTA
38% stent 39% PTA
NR
66% stent 39% PTA
NR
‡2.4
NR
SUPER
SMART
74 stent 76 PTA
123 mm stent 177 mm PTA
96% stent 91% PTA
57% stent 47% PTA
46% stent 43% PTA
13% stent 21% PTA
‡2.5
NR
RESILIENT
Lifestent
134 stent 72 PTA
70 mm stent 64 mm PTA
17% stent 18% PTA
35% stent 34% PTA
81% stent 37% PTA
13% stent 55% PTA
‡2.5
3%
†
Percent calcified lesions are reported for lesions with moderate or greater calcification. Value at 9 months of follow-up. Value at 2 years of follow-up. CTO: Chronic total occlusion; NR: Not reported; PSVR: Peak systolic velocity ratio; PTA: Percutaneous transluminal angioplasty; TLR: Target lesion revascularization. ‡ §
the roll-in portion of the study suggested excellent acute results; a separate two-center study reported primary patency rates at 12 months of 86% for treatment of short lesions [9,10]. While the Intracoil stent is FDA approved for use in the SFA, it is rarely used due to difficulty in accurate deployment, short available stent lengths and improved patency with newer iterations of nitinol SE stents. The Vienna Absolute Study randomized patients 1:1 to a 6-mm Dynalink or Absolute stent (Abbott Vascular, Santa Clara, CA, USA) versus balloon angioplasty of the SFA [11]. One hundred and four patients were enrolled with an average lesion length of 101 mm in the stent group and 92 mm in the balloon angioplasty group. The average length of the treated segment was 132 mm in the stent group and 127 mm in the angioplasty group. One-third of patients had a total occlusion of the SFA, and two-third of lesions were characterized as having moderate–severe calcification. About 57% of the patients had one stent implanted and 27% had two stents implanted. Of note, there was a 32% crossover rate from balloon angioplasty to stenting due to suboptimal results (>30% residual stenosis or flowlimiting dissection). Restenosis rates at 1 year based on duplex ultrasound peak systolic velocity ratio (PSVR) ‡2.4 favored stenting over angioplasty (37 vs 63%; p = 0.01). There was also a statistically significant difference in walking time and ankle brachial index (ABI) in favor of stenting at 12 months, and the lower rates of restenosis with stenting were sustained to 2 years [12]. Two-year follow-up also showed a trend toward decreased rates of target lesion revascularization (TLR) (37 vs 54%) with primary stenting. These early results suggested that nitinol SE stents are superior to balloon angioplasty for moderate length (80–150 mm) femoropopliteal lesions. 834
The FAST randomized patients 1:1 to placement of a Luminexx3 stent (Bard Inc., Tempe, AZ, USA) versus balloon angioplasty for shorter SFA lesions [13]. The mean lesion length for both groups was 45 mm, with 36% of the stented group having total occlusions compared with only 24% with occlusions in the balloon angioplasty group (p = 0.05). More than 50% of the patients were characterized as having none–mild calcification. Binary restenosis at 12 months PSVR ‡2.4 by duplex ultrasound was 38% in the balloon angioplasty (percutaneous transluminal angioplasty [PTA]) group and 31% in the stent group by intention-to-treat (ITT) analysis (p = 0.37). TLR at 12 months was also similar between the two groups (18% PTA and 14% stent; p = 0.5). The higher prevalence of total occlusions in the stenting arm, shorter lesion length compared with other studies and small sample size may have contributed to the equivalent rates of restenosis between the two treatment modalities. The ASTRON trial randomized patients 1:1 to the Astron stent (Biotronik GmbH, Berlin, Germany) versus balloon angioplasty in a total of 73 patients with mean lesion length of 82 mm in the stent group and 65 mm in the angioplasty group (p = 0.02) [14]. The average length of the treated segments was 98 and 71 mm in the stent and PTA groups (p = 0.01), respectively. More than one-third of the lesions were total occlusions. Fifty percent of the patients received one stent only and less than 10% had more than two stents placed. By ultrasound, the restenosis rates (based on a PSVR ‡2.4) in the stent and PTA groups at 12 months were 34% versus 61%, respectively (p = 0.02). The stent group also had a statistically significant increase in walking capacity compared with the PTA group. Expert Rev. Cardiovasc. Ther. 12(7), (2014)
Expert Review of Cardiovascular Therapy Downloaded from informahealthcare.com by Nyu Medical Center on 07/06/15 For personal use only.
Recent advances in SE stents for use in the superficial femoral & popliteal arteries
The SUPER trial was a multicenter UK-based randomized study of the SMART stent (Cordis, Warren, MA, USA) versus balloon angioplasty for the treatment of femoropopliteal lesions [15]. One hundred and fifty patients were randomized 1:1, and the mean lesion length was 123 mm in the stent group and 117 mm in the balloon angioplasty group. In addition to longer lesion lengths, the study had a very high prevalence of chronic occlusions (93.3%). At 12 months, primary patency (based on duplex ultrasound PSVR of ‡2.5) was 47.2% in the stent group versus 43.5% in the balloon angioplasty group (p = 0.7). Overall, these results showed no additional benefit of primary stenting compared with balloon angioplasty. Possible reasons for this include the poor overall primary patency as well as the high prevalence of chronic occlusions and subintimal angioplasty. In comparison, more recent stent designs have demonstrated significantly higher patency even in long lesions, suggesting that the results of the SUPER trial may not be generalizable to newer stent types that may have better patency with longer lesions. The RESILIENT study was a large multicenter randomized trial comparing the Lifestent (Bard Inc., Tempe, AZ, USA) to balloon angioplasty in the SFA and proximal popliteal artery [16]. Two hundred and six patients were randomized in a 2:1 fashion to stent versus balloon angioplasty. The average lesion length was 70 mm in the stent group and 64 mm in the PTA group. The percentage of total occlusions was low compared with previous studies (17–18%), and greater than 60% of lesions were characterized as having none–mild calcification. Forty percent of the patients in the PTA arm crossed over and had a stent placed due to suboptimal PTA result. The primary endpoint of the study was TLR at 12 months. Of note, patients in the PTA arm that received bailout stenting for flowlimiting dissection or suboptimal result were classified as a TLR in the ITT analysis. This caused the primary patency endpoint (restenosis based on a PSVR ‡2.5) in the ITT analysis to heavily favor stenting over PTA at 1-year follow-up (81 vs 36%; p < 0.0001). In the as-treated group, despite having longer lesions in the stent group (63 vs 47 mm; p < 0.01), primary patency was also significantly higher at 12 months (80 vs 61%; p = 0.03) [16]. However, overall freedom from TLR at 12 months was not statistically different for the two modalities based on the as-treated analysis (86 vs 75%; p = 0.15). At 3-year follow-up, freedom from TLR was significantly improved in patients randomized to stent placement based on the ITT group (75.5 vs 41.8%; p < 0.001) but was not significantly different when comparing the as-treated group (75.5% for stenting vs 70.1% for balloon angioplasty with provisional stenting) [17]. In summary, the majority of randomized studies supported the superiority of nitinol stents for moderate to long lesions of the SFA using currently available technologies. For lesions in the range of 40 mm, a strategy of stand-alone balloon angioplasty is reasonable, given the results of the FAST trial. For lesions exceeding 80 mm, current studies support a strategy of primary stenting based on duplex restenosis, while recognizing informahealthcare.com
Review
that not all cases of restenosis require reintervention. For lesions exceeding 150 mm, even a reasonable acute balloon angioplasty result is associated with high rates of subsequent restenosis, and primary stenting may be the preferred modality [18]. These issues of outcomes with longer lesion lengths have been addressed in some recent registry studies and the VIASTAR trial (see below). Registry studies of nitinol stents
A number of studies have reported registry results of newer generation nitinol stents in both the SFA and proximal popliteal artery (TABLE 2). In general, these studies have shown incremental improvement in primary patency for treatment of moderate length SFA and proximal popliteal artery lesions. Importantly, most of these studies have also included core lab adjudicated x-rays that demonstrated significantly lower rates or in some cases, no stent fractures with newer stent designs. This improved conformability and resistance to fracture may in some cases account for the improved rates of long-term primary patency with newer generation stents. One limitation of these registries is the lack of a comparator group with balloon angioplasty alone although the presence of core laboratory adjudication and dedicated duplex follow-up for most of these studies has provided important data regarding the long-term results of stent placement. Everflex stent
The Everflex stent (Covidien, Mansfield, MA, USA) is a newer generation nitinol stent with spiral connections between nitinol-linking segments, which increase conformability of the stent compared with earlier generation stents. The DURABILITY I and DURABILITY II registries have provided encouraging results with this stent for the treatment of both moderate length (DURABILITY I) and long (DURABILITY II) lesions. The Durability I trial was a multicenter study of the EverFlex stent in SFA lesions [19]. This study enrolled 151 patients with symptomatic PAD ranging from Rutherford categories 2–5. The mean lesion length was 96 mm, and 40% of the lesions were total occlusions. More than half of the lesions had no significant calcification. The study was designed to use only one stent, with a maximum available stent length of 150 mm. The primary endpoint of the study was freedom from restenosis (based on a PSVR
