Bypass grafting is the treatment of choice for chronic total occlusions (CTO) of the superficial femoral artery (SFA), with a favourable technical success rate and clinical prognosis (Norgren et al. 2007). However, the following occlusion of the femoropopliteal arterial bypass in patients with CLI remains a significant problem, that hardly challenges vascular surgeons and interventional radiologists due to an attendant increased mortality and morbidity (Betz et al. 2012; Greenberg and Ouriel 1998). The ideal treatment for failed femoropopliteal bypass in patients with CLI and CTOs of the native SFA would minimize postoperative morbidity and achieve satisfactory limb salvage and long-term patency rates (Li et al. 2018). After a bypass graft failure has occurred, the possible targets of intervention are the bypass graft itself or the native SFA. Among bypass graft interventions, surgical or endovascular approaches can be distinguished. Performing a secondary femoropopliteal bypass is still considered the standard of care, although it is associated with a higher complication rate (perioperative morbidity of 25 %), 66 % limb salvage rate at 5 years and lower mid-term patency rate in comparison with primary bypass (Baldwin et al. 2004; Belkin et al. 1995). Taha et al. reported a significantly higher overall mortality rate at 30 days and 1 year in the patients requiring open reintervention (Taha et al. 2015). Besides, advanced age, lack of a good great saphenous vein, anastomosis’ pseudoaneurysms and high surgical risks make surgical approach not always suitable. An alternative surgical strategy is to perform open thrombectomy and surgical revision of the bypass graft, with or without a patch. Despite an acceptable technical success rate, this technique correlates with poor primary patency and limb salvage rates: 40 and 45 %, respectively, at 30 months, according to Quinones-Baldrich et al. (Quinones-Baldrich et al. 1991). Options to achieve endovascular recanalization of bypass graft include mechanical thrombectomy and catheter-directed thrombolysis (CDT). CDT, available for patients presenting with acute limb ischemia (ALI), provides a high technical success rate, around 84 % (Gardiner et al. 1989). Nevertheless, the median patency is 8 months, the patency rate at 5 years is 19–28 % and the limb salvage rate at 5 years is 55 % (Nehler et al. 2003; Nackman et al. 1997). To these data are added the not negligible complications, especially hemorrhagic, and the frequent need to add a PTA treatment, after the CDT has been performed. For the aforementioned reasons, clinical outcome data about CDT remains inconsistent. More recently mechanical thrombectomy devices have been utilized alone or in combination with thrombolytics to achieve more rapid lysis (Shammas et al. 2008). Mechanical thrombectomy has been highly effective in fresh thrombus but much less effective in older, more organized thrombus, with a primary patency rate of 50 % at 12 months (Domínguez Paillacho et al. 2018; Kalinowski and Waqner 2003). Hemolysis, residual thrombus, and distal embolization are recognized complications of isolated mechanical lysis.
After a femoropopliteal bypass graft failure has occurred, as an alternative to bypass itself, the other possible target of intervention is the native SFA. Over the past few years, angioplasty has been commonly used to treat chronic total occlusions of the native SFA, with a good technical success rate and clinical prognosis (Mewissen 2004). Besides, contemporary vascular literature (Baril et al. 2010; Laganà et al. 2011; Dosluoglu et al. 2008) on primary endovascular treatment of TASC II C and D femoropopliteal lesions has shown acceptable patency rates compared with those recorded after femoropopliteal bypass, also thanks to the development of endovascular techniques (such as subintimal angioplasty or SAFARI technique) and tools (re-entry devices, stents, etc.) (Hua et al. 2013). Hence, such a scientific background, characterized by the scarcity of alternative endovascular techniques (CDT, mechanical thrombectomy) that are effective and by the presence of still partial but interesting data concerning the patency of TASC II C and D lesions treated with endovascular recanalization as first-therapy, explains the rationale for considering endovascular recanalization of native SFA CTOs as a treatment hypothesis after femoropopliteal bypass failure, in patients with CLI who refuse surgery or are considered unfit for surgery.
In this study, we report the results of a retrospective analysis of data, regarding patients with CLI after the failure of femoropopliteal bypass who had undergone endovascular recanalization of CTOs of the native SFA. There was a high technical success rate (94.4 %). The experience developed with advanced endovascular techniques (such as subintimal angioplasty or SAFARI technique) and tools (re-entry devices) has certainly contributed to the results achieved, enabling the treatment of more challenging arterial lesions. Many secondary endovascular procedures for acute thrombosis have been performed, so that the primary patency rate was low at both 1 year and 5 years (61 and 46 %, respectively) but the secondary patency rate was considerable, at both 1 year and 5 years (93 and 61 %, respectively). In some cases, some authors have used the term “major adverse limb events” (MALE) which definition includes endovascular reinterventions in the same leg. This may explain why in literature there is high variability in reporting rates of adverse limb events (Davies and El-Sayed 2017), considering that many secondary endovascular procedures are often performed. The most interesting recorded results were the amputation-free and the limb salvage rates, which were approximately 93 and 94 % at 1 year, 76 and 88 % at 5 years, respectively. Thus, long-term limb salvage was achieved in the majority of patients. This figure is partly attributable to the preservation and enhancement of the arterial patrimony of the collateral branches, guaranteed by profunda femoris artery and by the endovascular recanalization of the native SFA with intraluminal approach and often sacrificed by the surgical approach. Even in the case of main vessel reocclusion, the collateral branches by SFA and profunda femoris artery could guarantee a blood supply, sufficient to maintain tissue integrity. Furthermore, distal BTK lesions can be treated at the same time, improving outflow. Patency and limb salvage rates at 7 years show interesting results too, but survivor function at the far right of a Kaplan-Meier survival curve should be interpreted cautiously since there are fewer patients - low numbers at risk - remaining in the study group and the survival estimates are not as accurate (Rich et al. 2010). Thus, it should be kept in mind that the Kaplan-Meier method’s main focus is on the entire curve of mortality rather than on the traditional clinical concern with rates at fixed periodic intervals (Feinstein 1985).
The data presented above represent one of the largest and longest follow-ups to date and are comparable with those published previously in the few case-series studies found in the literature, concerning this topic. Gandini (Gandini et al. 2009) reported a technical success rate of 93.7 %, a secondary patency rate of 73.5 % at 3 years and a limb salvage rate of 88 % at 3 years. Davies (Davies and El-Sayed 2017) demonstrated in a retrospective review, comparing the outcomes of bypass redoing versus native SFA recanalization in patients with symptomatic femoropopliteal bypass occlusion, that the SFA recanalization group, treated with direct stenting, presented an amputation-free survival rate of 33 % ± 9 % at 3 years. Li Z (Li et al. 2018) described a technical success rate of 95.6 %, a secondary patency rate of 61 % at 3 years and a limb salvage rate of 95 % at 3 years. In other case series, secondary patency rates at 1 year ranged from 44 to 96 % and limb salvage rates were 65–96 % at 2 years (Kawarada and Yokoi 2010; Yin et al. 2015; Wrigley et al. 2014).
Furthermore, the data presented in our study are comparable to the results of the primary endovascular treatment of TASC II C and D femoropopliteal lesions. Guo (Guo et al. 2015) reported a technical success rate of 95 % and a secondary patency rate of 63 % at 3 years after endovascular treatment of TASC II D femoropopliteal lesions. Dias-Neto and others (Dias-Neto et al. 2018; Joo et al. 2017; Veraldi et al. 2018) reported similar mean procedure duration and fluoroscopy time.
Data analysis reveals that considering the long-term outcome, endovascular recanalization of the native SFA may not be inferior to the bypass redoing too, the current standard of care. Previously published data on secondary femoropopliteal bypass report a primary patency rate of 28–57 % and a limb salvage rate of 66-72.4 % at 5 years, in patients with CLI (Belkin et al. 1995; Yang et al. 1991; Edwards et al. 1990). A more recent retrospective review by Davies (Davies and El-Sayed 2017) has demonstrated at 3 years an amputation-free survival rate of 56 % in the bypass graft group. Besides, when the results are examined, the potential risk of selection bias cannot be ignored. Endovascular recanalization is generally offered only to patients who are unfit for surgery or who refuse a second surgical approach. It is possible, therefore, that the poor general clinical conditions of these patients affect the specific clinical outcome of the endovascular approach in a pejorative sense. Consequently, since the presence of selection bias in the study population cannot be excluded, the patency and limb salvage rates become even more interesting, when compared to those detected with a bypass redoing.
Therefore, in patients with CLI and failed femoropopliteal bypass, if the endovascular recanalization of the native SFA CTOs is a safe and considerable alternative, with high long-term limb salvage rates, to bypass redoing, even in those patients fit for surgery, remains an open question. Testing this hypothesis by performing a randomized controlled trial could be an interesting future perspective derived from this study. Although the data available to date do not allow to reach definitive conclusions, at least they suggest that the bypass redoing should no longer be considered as an automatic and obvious choice in all cases.
Due to a lack of previously published data, there is a shortage in the literature regarding the risk factors impacting the primary patency loss in patients who underwent endovascular recanalization of the native SFA CTOs after femoropopliteal bypass failure. By univariate analysis, statistically significant predictors of primary patency loss were diabetes mellitus, chronic renal insufficiency (eGFR < 90 mL/min), tissue loss at clinical presentation, bypass target to the below-knee popliteal artery, lesion length ≥ 30 cm, TASC II D lesion, BTK runoff (1 vessel) and stents positioned per patient ≥ 3. By multivariate analysis, statistically significant predictors of primary patency loss were diabetes mellitus, chronic renal insufficiency (eGFR < 90 mL/min), bypass target to the below-knee popliteal artery, lesion length ≥ 30 cm, TASC II D lesion and BTK runoff (1 vessel). The contemporary literature on the endovascular treatment of peripheral artery disease (PAD) demonstrates that diabetes is one of the strongest risk factors for primary patency loss (DeRubertis et al. 2007). Our study has found a similar result both in the univariate (HR = 4.2; CI = 2.1–9.1; P = 0.03) and in the multivariate (HR = 6.1; CI = 1.1–23.8; P = 0.04) analysis. Hence, greater consideration should be given when native lesions are endovascularly treated in diabetic patients since they were more likely to have accelerated disease progression over time due to their diabetic status (Bakken et al. 2007). Chronic renal insufficiency (eGFR < 90 mL/min) independently predicts primary patency loss, due to its known capacity to cause a more advanced and rapidly progressive arterial occlusive disease (Iida et al. 2014). In agreement with previously published data by Scali ST (Scali et al. 2011), a BTK runoff of one vessel is a strong statistically significant predictor of primary patency loss, perhaps also a surrogate of the overall duration, severity and limb-extension of the atherosclerotic disease. Another important finding is that a lesion length ≥ 30 cm and a TASC II D lesion are predictors of primary patency loss. This finding is in contrast with one of the few previously published reports on the endovascular recanalization of the native SFA CTOs in patients with CLI after failed femoropopliteal bypass (Li et al. 2018), whose regression analysis had not shown significant influence of a lesion length > 20 cm and a TASC II D lesion on the primary patency loss, but it’s in agreement with the historical and contemporary vascular literature on primary endovascular therapy for lower limb lesions (Jørgensen et al. 1991; Iida et al. 2014). In particular, 2017 ESC guidelines on the diagnosis and treatment of PAD (Aboyans et al. 2018) clearly state that if the occlusion/stenosis is > 25 cm, endovascular recanalization is still possible, but better long-term patency is achieved with surgical bypass, especially when using the great saphenous vein, although it does not distinguish between primary patency and secondary patency rates.
The below-knee popliteal artery bypass target heralds the presence of a more extensive TASC II D disease of the native SFA, strongly associated with a higher rate of restenosis after a percutaneous intervention (Owens et al. 2008a, b). It’s well-known that patients with tissue loss at clinical presentation have poorer outcomes (Setacci et al. 2009), not only due to atherosclerotic disease extended to BTK-district but also because of poorer blood supply by collateral circulation at the femoro-popliteal district, in turn, a sign of a severe and extended disease of the native SFA. The last predictor of primary patency loss is a number ≥ 3 of stents positioned per patient. The lack of significance according to the multivariate analysis and the wide CI generated by the univariate analysis (HR = 3.9; CI = 1.2–14.9; P = 0.04) might suggest the imprecision of the univariate estimate. Hence, a number ≥ 3 of stents positioned per patient might be just a surrogate for other risk factors independently associated with a poorer outcome and a PTA failure, such as a TASC II D lesion, a more extensive or calcified disease. In addition, there is growing evidence on the effectiveness of the full metal jacket approach in the treatment of TASC II C and D lesions (Laganà et al. 2011; Philips et al. 2018).
Limitations of the study are the lack of a control group, the single-centre setting, the retrospectivity of the analysis and the scarcity of data in the literature, necessary to evaluate the congruence and the consistency of the data presented.