Although SIA is currently widely used and worldwide experience with the technique is growing, there is still considerable doubt regarding the method and its results. This is mainly due to lack of evidence from randomized clinical trials comparing SIA with intraluminal angioplasty. However, SIA is known to yield high percentages of technical success and acceptable long-term clinical patency and limb-salvage rates.
The comparison between subintimal and intraluminal is difficult and unfair as both are used in different situations as regard the patency rate. But we tried to point out the predictors for subintimal angioplasty that can be used in the future.
First, the lesion morphology after angioplasty is different. The atherosclerotic plaque remains in the flow channel after intraluminal angioplasty, whereas a subintimal flow channel is devoid of exposed plaque except at entry and re-entry points. This could alter arterial wall remodeling after SIA from those observed with IBA. Hence, the role of neo-intimal hyperplasia after stent placement in a subintimal channel is unknown. Second, the types of lesions in each group are different. Whereas intraluminal angioplasty can be used for segments with stenosis or short occlusions, subintimal angioplasty is used for segments with short or long occlusions. Also, as suggested by the worsening stent results with increasing TASC lesion, the majority of SIA are performed for TASC C and D lesions.
In 2013, Antoniou and coauthors published a meta-analysis of endovascular versus surgical reconstruction of femoropopliteal arterial disease including a total of 2817 patients (1387 open, 1430 endovascular). Comparing our patient’s demographic characteristics, risk factors and co-morbidities to those of patients in their meta-analysis, we will find that gender was almost the same while our mean age was lower [8
]. Regarding the risk factors, 91.2% of our patients were diabetics compared to only 43% in Antoniou et al. other risk factors were almost the same. Our lower mean age may be attributed to that all our patients suffer from |CLI and 90% were diabetic
and this reflect the burden of comorbidities with higher mortalities. Increased life stress and obesity predispose to our high incidence of diabetes in Egypt. All of the cases included in our study presented with critical limb ischemia and about 75% of them tissue loss. Moreover, about 57% of the cases had lesions more than 10 cm in length, about 62% of the cases chronic total occlusion was found, and this can be explained by that all of our cases had critical limb ischemia. As many of our patients were diabetic and diabetes is characterized by extensive and distal vessels disease that may explain the high number of tissue loss in our study. It is commonly documented that a more severe state of the limb, especially Rutherford 6 with ulcer or gangrene are more likely results in a higher major amputation rate. The need for major amputation is twofold higher in patients with ulcers or gangrene than in patients with only rest pain as severe tissue loss reflects the great load of the disease [12
It is noticed that in lesions less than 10 cm length, the wire usually passed transluminally, but in lesions more than 10 cm in length the wire passed subintimally in a considerable percent of cases (about one third of the cases with lesion length more than 10 cm the wire passed subintimally with significant P value (P value <0.05). Vraux et al. have reported that the length of the occlusion (>10 cm) is a predictor of SA technical success and patency [13
]. Baril et al. in 2010 stated that endovascular interventions for TASC II D lesions can be safely performed with excellent hemodynamic improvement and limb salvage rates [14
]. Arterial calcification, poor runoff, diabetes, treatment for chronic limb ischemia as opposed to claudication, and lesion length are the variables most frequently postulated to affect patency. Some articles suggest that calcification in the wall of the occluded artery makes recanalization difficult and predisposes to technical failure, but others could not confirm this effect. Although intuitively, occlusions are thought to be more difficult to treat than stenosis, results have been conflicting. All of our patients were treated for chronic limb ischemia, and we found primary patency to be 18% at 3 years [15
]. Noticing that most of our patients were diabetics where Vascular calcifications are usually severe and diffuse, and arterial occlusive disease
occurs mainly at the level of the infrapopliteal arteries, impairing runoff vessels and, thus, reducing chances and success of intervention [16
]. Also the risks of intervention are usually higher in the diabetic population due to the comorbidities [17
We classified the lesions according to the TASC II classification, and more than 50% of the cases were TASC II D lesions. Moreover, subintimal passage of the wire was observed in cases with lesions classified as TASC II D and also that was found to be statistically significant. (P value<0.05). The high percentage of TASC D cases reflect that the CLI to occur need extensive disease and long occlusion not simply short stenosis or occlusion and the same time reflect the difficulties in management of such difficult lesions and the technical success of PTA and could be used as the 1st choice [18
]. However it was mentioned by Bakken et al. and Lida et al. that TASC A &B can cause CLI as diabetic patient had in addition microvascular deficiency (microangiopathy) because the presence of DM appears to reduce blood flow to the microvascular bed via arterio-venous fistulae leading to symptomatic disease with less advanced femero-popliteal disease [11
]. Regarding the runoff vessels about 50% of our cases had single runoff vessel and this is may be due to the fact that more than 90% of our patients were diabetics. While the average percent of patients suffering from critical limb ischemia in the meta-analysis done by Antoniou et al. was 66% [8
]. This may reflect the difficulties in management of our patients [19
]. Poor peripheral runoff is also associated with poorer long-term results. Long-term patency rates of 30% in limbs with poor runoff, versus 52% with good runoff [20
We used the ipsilateral femoral access as the first option whenever it was possible. The second option was the contralateral femoral approach. In one case only we used the brachial access as the lesion was flush to the SFA and the patient had chronic total occlusion of the common iliac artery in the contralateral limb and it was a symptomatic. In 3 cases we had to use the ipsilateral popliteal approach due the failure to pass the lesion via the femoral approach.
This study did not use several other techniques described for use in difficult passage for long femoropopliteal lesions. Retrograde passage through popliteal access has been used mainly for flush SFA occlusions if contralateral approach was failed. Usually the retrograde puncture of the popliteal artery was done by using duplex ultrasonography, and SI-PTA is performed from the distal SFA to the proximal SFA, which is opposite the direction used for the standard approach. The retrograde SFA SI-PTA approach has a reported patency rate of 62% at 1 year [21
This study also did not use the technique described by Balas et al. which approaches flush occlusions of the SFA with a combination of open surgery and endovascular techniques [22
Regarding the passage of the wire, in about 75.5% of the cases the wire passed transluminally while in only about 19.5% of the cases the wire passed subintimally. Although it was mentioned by Lazaris et al. that Subintimal angioplasty is a different technique to transluminal
angioplasty; not only are there technical differences but also because SA achieves recanalization of long arterial occlusions which PTA cannot and they argued that in transluminal angioplasty selection on anatomical ground is important because the ideal patient will be the one with focal disease. However because of the presence of diffuse disease in chronic CLI, transluminal angioplasty is only applicable in a small proportion of CLI patients. In contrast, SA due to its effectiveness in long occlusions can be applied to most patients with CLI. Consequently SA can be considered as an alternative to open surgery for these patients. The treatment is relatively atraumatic, complications are rare and in most cases treated by endovascular techniques.
Hynes et al. have reported the number of attempted revascularisations to have doubled since the introduction of the subintimal
]. Awad et al. used the subintimal technique routinely in all femoropopliteal occlusions, whereas stenoses were usually treated intraluminally [24
]. Antusevas et al. in 2008 found that Results from subintimal angioplasty of superficial femoral artery occlusions was superior to the results of PTA. Subintimal angioplasty has also provided a new method of managing occlusions, which has substantially improved the entire field but specifically has changed lower extremity revascularization [25
Since long complex lesions are usually present in CLI patients, successful endovascular recanalisation of the SFA can sometimes only be performed with subintimal angioplasty (SIA). SIA has been associated with high limb salvage rates between 85% and 90% at 1 year, even despite a low 50% 1-year primary patency rate [26
These results were recently confirmed by Bolia et al. and Setacci et al. with primary success rates of 80% and 83.5% and limb salvage rates of 85% and 88% at 1 year, respectively [27
In a study done by Köchera, et al. in 2010 aiming at retrospective assessment in mid-term outcomes of subintimal angioplasty of chronic arterial occlusions in femoro-popliteal region, Technical success was achieved in 86.46% . Primary patency rate was 83.1%, 67.5% , 58% and 48.4% at 6, 12, 24 and 36 months respectively and the study concluded that subintimal recanalisation is a simple and safe procedure for treatment of chronic peripheral arterial occlusions with high primary technical success rate, acceptable primary patency rate, low percentage of complications and mortality is as low as nil. Subintimal angioplasty is definitely advantageous and fast method in patients with critical limb ischemia
with high possibility of limb salvage
PSA offers a number of advantages meanwhile in terms of the technique, no specialized equipment or materials are necessary. It does not require extensive experience by the operators, the procedure is inexpensive, and it is relatively non-traumatic and does not preclude subsequent surgery should it fail to recanalize an occlusion. It is applicable in a large number of situations where other techniques are likely to fail, for example in long occlusions, moderately calcified vessels, previously failed intraluminal approach and in hard occlusions of long standing. For long occlusions of the tibial artery, flush SFA occlusion, popliteal occlusions extending into the trifurcation, in the presence of a large proximal collateral, common femoral occlusions extending into the bifurcation, and when a perforation occurs in an attempted SFA recanalization, PSA is probably the only technique that allows a successful outcome to be achieved in the vast majority of cases. It was the hope for patients who are poor candidates for general anaesthesia or who do not have an adequate vein conduit for a distal bypass may be successfully treated. The procedure rarely compromises a subsequent surgical option in case of a failed angioplasty, and is also more readily repeatable compared to surgery [31
However, there is a serious disadvantage of PSA, which may make the patient
worse rather than better. There is a potential risk of damage to important collaterals distal to the occlusion when these are included in the dissected portion. When important collaterals are compromised without achieving a haemodynamically viable channel in the main artery, the patient’s distal circulation will be compromised and urgent bypass surgery will be required to restore circulation to the distal leg. It is therefore crucially important that a dissection is not extended too far distal to the occlusion, particularly early on in a doctor’s experience [31
]. But in a study done by Treiman et al. where they do support the concept that failed recanalization does not alter or jeopardize subsequent bypass [15
In the current study, The overall technical success to pass the lesion was 95%. Antoniou et al. reported 91% technical success in the endovascular group with no significant heterogeneity among the studies. It should be noticed that the meta-analysis included studies done many years ago and nowadays with the rapid development of endovascular tools and their quality we think that 95% technical success using the simplest endovascular tools for treating critical limb ischemia patients is satisfactory [8
]. In a study done by Myers and coworkers shows similar rate, The initial technical success rate of 92.6% and the patency rate of 82.3% at 6 months [23
]. Sidhu et al. mentioned that severe calcification was the predominant cause of failure, as it is difficult to reenter the distal lumen. Also,The absence of a proximal SFA stump presents difficulty in initiating the subintimal plane, which is another cause for technical failure [32
The nature of the lesion affects both the success rate and the long-term patency: more distal and longer lesions are more technically challenging and less likely to stay open, and the presence of calcification is associated with a lower success rate. The major causes of technical failure in SIA are failure of reentry and elastic recoil [33
The overall primary patency rate in our study at 12 months was 54.7% in comparison to about 62% in three randomized trials and four observational studies and this inferior result may be due to the fact that most of our patients were diabetic with TASC II C or D category and with long total occlusions [8
].The primary patency rate at 12 months for the transluminal approach was 56.8%, while for the subintimal approach was 46.7%, so there was no statistical significance between the two approaches (P value 0.55).
In the study of Sidhu et al. the cumulative primary patency at 6 and 12 months was 90% and 73%, respectively and Primary patency of SA is lower compared to surgical bypass, especially that with autogenous vein. However, patency can be maintained with secondary procedures with little additional morbidity or mortality. Therefore, SA can be considered a primary procedure even in patients with TASC II C/D lesions. It is important to avoid damage to the target outflow vessel thereby preserving future options for operative revascularization. The secondary patency rate at 6 and 12 months was 94% and 85%, respectively [32
Norgren et al. reported that the 1 year primary patency after PTA alone for the femoropopliteal segment occlusive lesions is 77% for the stenosis only and 63% for occlusions. Regarding the 1 year primary patency of PTA and stenting for the femoropopliteal lesions they reported 1 year primary patency of 75% for the stenosis and 73% for the occlusions [6
]. Data regarding primary patency rates at 1 year after SIA vary widely. A recent meta-analyses of several SIA studies, including 1549 and 2810 limbs, respectively, estimated that 1-year primary patency rate was approximately 50%. Limb salvage is the most widely accepted clinical outcome measure in the CLI population [33
]. The overall limb salvage in our study was 64.9% and the reason beneath the fact that the limb salvage is higher than patency rates is that all of the cases had critical limb ischemia and endovascular intervention may provide sufficient blood supply needed for healing then by the time the vessels is occluded the demand of blood supply is decreased and the collateral developed is enough for the tissue viability. The limb salvage at 12 months for the transluminal approach was 66.1%, while for the subintimal approach was 60%, so there was no statistical significance between the two approaches (P value 0.58).
In our study we just used the simplest endovascular tools. Evolving endovascular strategies embrace new technologies in an attempt to improve the safety and efficacy of revascularization procedures for lower extremity arterial occlusive disease. Drug-eluting stents and drug coated balloons, and the use of stent grafts are currently being evaluated in the primary treatment of femoropopliteal segment disease for selected patients. Research on polymer-based and alloy-based bioabsorbable stents is a promising field, which, if substantiated, may change endovascular treatment
paradigms. Such novel treatments along with the imperative understanding of medical treatment focused on the individual patient’s needs and expectations may constitute areas of future research [8
Regarding the complications the mortality rate was 1.3% and the overall complication rate was 37%. It is noticed that in our study there is a high percent of dissection (about 31%) and this is may be due to the fact that more than half of our cases are TASC II D and more than 90% of our cases are diabetics leading to the presence of heavily calcifications.
There is an explanation mentioned by Giles et al. rationalize the high rate of complications observed in endovascular group that the patients who preferentially undergo a percutaneous intervention tend to be sicker than patients in whom bypasses are the first line of treatment. An attempt at percutaneous intervention may be per formed as a “salvage” procedure in patients who have limited life expectancies and extensive comorbidities who would have otherwise undergone a primary amputation, which is associated with perioperative mortality rates of 5% to 17% Although the minimally invasive nature of infrapopliteal PTA has obvious appeal, it also has potential disadvantages. These may include conversion of an elective to emergency procedure, loss of bypass targets, a less durable solution, lengthy procedures causing excessive radiation exposure, and the potential for rising costs of care if multiple interventions are necessary. The delay to surgery caused by an inadequate or failed intervention could cause in-creased ischemia and lead to worsening wounds, minor amputations, and even limb loss, despite the ability to construct a durable bypass graft [39
On the contrary, in a study done by Faglia et al. the survival of amputated patients who had previously undergone revascularization was significantly better than that of non revascularized amputees, even when unable to avoid major amputation. In addition to already demonstrated that this revascularization reduces the rate of major amputation. Moreover, our data indicated that the rate of below-the-knee amputation in PTA patients was significantly higher than that of nonrevascularized patients, as well as than that of amputated patients because of BPG closure. The outcomes of below-the-knee amputation are superior to those of the above-the-knee amputation. They further encourage performing revascularization in all diabetic patients with CLI [18
In metaanalysis done by Markos et al. Overall complication rates of SIA are reported as between 6% and 17%. Definitions of complications differ widely, and there is very limited evidence about factors affecting the complication rate. The complication rate of SIA is no higher than for PTA, and the risk of major adverse events is lower in SIA than surgery. The amputation rate after SIA was reported as 2.2% in patients with CLI [43