Peripheral arterial disease (PAD), also known as lower extremity arterial occlusive disease (PAOD), is the narrowing or occlusion of the lumen of the lower extremity arteries due to atherosclerosis or inflammation, and is an important manifestation of systemic atherosclerosis. It is an important manifestation of systemic atherosclerosis. In recent years, with the development of economy, the incidence of type 2 diabetes has been increasing. type 2 diabetes and atherosclerotic disease share a common pathophysiological basis and often cluster together; type 2 diabetes peripheral vascular disease is often combined with atherosclerotic vascular disease, which is an important component of PAD. type 2 diabetes and PAD often manifest as arteries of the lower extremities, especially the distal arteries of the N and knee. It is a major cause of critical limb ischemia (CLI) and non-traumatic low level amputation. Due to the continuous improvement of endoluminal techniques and equipment, percutaneous transluminal angioplasty (PTA) is increasingly used to treat occlusive lesions of lower limb arteries, especially the infrapopliteal artery. This article reviews the current status and strategies of endoluminal treatment of PAD as follows: Zhang Tong, Department of Peripheral Vascular Disease, Xiyuan Hospital, Chinese Academy of Traditional Chinese Medicine
I. Prevalence and early diagnosis of PAD.
Risk factors for the occurrence of PAD include: gender, advanced age, smoking history, diabetes, hypertension, dyslipidemia, inflammatory status, racial genetics, homocysteinemia, chronic renal insufficiency and lack of exercise. Epidemiological studies have shown [1] that the prevalence of PAD is about 3-10% in the population; in those aged 70 years or older, the prevalence can be as high as 15-20%. In people with combined diabetes, the risk of PAD increases by 26% for every 1% increase in glycosylated hemoglobin (HbA1c). Our survey of diabetic patients aged >50 years showed that the prevalence of PAD in such patients was 19.47% (up to 31.9% in those aged 70 years or older) [2]. Most patients with PAD do not have typical clinical manifestations. Studies of individuals with at least one risk factor for PAD have shown that the prevalence of asymptomatic PAD can be as high as 29%.
Intermittent claudication (IC) is the most typical clinical symptom in patients with PAD who are unable to walk long distances for reasons such as severe cardiopulmonary dysfunction. Patients with PAD who are unable to walk long distances due to severe cardiopulmonary impairment do not exhibit typical clinical symptoms. In patients with diabetes mellitus and peripheral neuropathy, the early manifestations of PAD may be atypical or asymptomatic. However, studies still show that the risk of IC, progression to CLI and amputation is 2, 4 and 5-10 times higher in diabetic patients than in non-diabetic patients, respectively.
In response to the low awareness of PAD among clinicians and patients, and the late diagnosis of PAD, the American College of Cardiology and the Heart Association (ACC/AHA) jointly proposed guidelines for the treatment of PAD in 2006, pointing out that detailed clinical examination and related ancillary tests such as Ankle Brachial Index (ABI) should be performed for patients at high risk of PAD, especially those with combined diabetes. ABI testing is useful for the diagnosis and evaluation of PAD in the absence of typical clinical manifestations [1]. ABI is still recommended for the screening of PAD, progression of the disease and assessment of the treatment effect due to its simple, rapid and non-invasive characteristics [3].
II. Indications and contraindications for endovenous treatment of PAD.
When the degree of ischemia is assessed above Fontaine grade II, i.e., when clinical ischemic symptoms such as IC, or CLI (resting pain or tissue loss) with limited quality of life and reduced mobility are present, angiography, MRA or CTA, and arterial Doppler ultrasound should be performed on the ischemic limb to clarify the site of the lesion and to perform revascularization including endovascularization [4]. Among the above-mentioned vascular morphological examinations, if the luminal stenosis exceeds 50% or is occluded, regardless of the length and shape of the lesion, it is an indication for revascularization [5].
There are no absolute contraindications to endoluminal treatment. It is generally accepted that intracavitary therapy is contraindicated in patients with NYHA cardiac function class III or IV, or in patients with unstable hemodynamic parameters. In addition, allergy to contrast agents, inability to tolerate antiplatelet agents or heparin, and patients with renal insufficiency requiring special management are relative contraindications to treatment.
III. Changes in the scope of application of endovascular luminal therapy for PAD.
Hemodynamic reconstruction includes endoluminal angioplasty and surgical bypass surgery, the purpose of which is to reconstruct the blood flow from the lower extremity directly to the plantar aspect of the foot. The broad definition of endoluminal angioplasty includes balloon dilatation angioplasty, balloon cutting angioplasty, cryoangioplasty, directional spot fast resection, annular spot fast spin resection, laser spot fast resection and stent placement; balloon dilatation angioplasty is most widely used in PAD, especially in infrapopliteal artery lesions.
In 2002, the Trans-Atlantic Inter-Society Consensus (TASC) proposed morphologic classification and treatment recommendations for PAD according to the extent and scope of lower extremity arterial lesions, which was revised in 2007. Type A and B lesions are mild and endovascular treatment is recommended; Type C and D lesions are more severe and complex and surgical bypass is recommended. However, with the improvement of endoluminal therapy techniques and equipment, the application of endoluminal therapy has gradually expanded and is now used selectively in many centers for the treatment of TASC type C and D lesions [6]. A study at the Massachusetts General Hospital of Harvard Medical School showed that the mid-term initial patency rate after femoral N artery PTA was associated with TASC classification and that TASC type C/D lesions often required secondary PTA treatment. The BASIL study also showed that autologous vein bypass may have a higher rate of limb preservation and survival in patients with a long life expectancy and available veins; however, because of the effectiveness of PTA as a first-line treatment for CLI However, because PTA is comparable to surgical bypass as a first-line treatment for CLI and is relatively inexpensive and does not interfere with subsequent surgical treatment, PTA is still recommended for patients with indications, especially those with a life expectancy of less than two years [7]. Endovascular treatment can be repeated and is therefore the treatment of choice; endovascular treatment can also be performed in patients who have failed surgical bypass to save a limb that is at risk of amputation [8]. The impact of failure of the preferred endoluminal treatment on subsequent surgical bypass is controversial [7,9], but there are few reports. In addition, in patients with diabetes mellitus and CLI, peripheral vascular disease is mainly manifested by occlusive lesions in the three lower knee arteries, especially in the long segment of the tibial artery [10].PTA has been recognized as a first-line treatment for stenosis and occlusive lesions in the lower knee arteries due to its safety, efficacy and reproducibility of treatment and similar limb preservation rates compared to surgical bypass surgery [11].
In 2007, Graziani et al. proposed a new classification of lower extremity arterial lesions including the infrapopliteal artery based on the characteristics of peripheral vascular lesions in diabetic patients [ 10]. 10]. This method classifies lower extremity arterial lesions into 7 grades, with two occlusions and multiple stenoses in the tibiofibular and/or N femoral arteries being grade 4 lesions; and three occlusions and multiple stenoses in three arteries being grade 6 lesions. A study of patients with diabetes mellitus and CLI showed that 63% of patients had lesions between grades 4 and 6. The clinical applicability of this classification needs to be further evaluated.
IV. Objectives of endoluminal therapy and evaluation of treatment outcome.
The goals of intracavitary therapy are: (i) to preserve limb function and reduce the amputation plane; (ii) to establish blood supply directly to the foot lesion and promote foot ulcer healing; and (iii) to improve symptoms such as ischemic pain and improve quality of life.
PAD, especially in patients with combined diabetes mellitus, requires significantly more blood supply when the foot breaks down due to trauma, etc. Maintaining vascular patency and improving local blood circulation after PTA is not the ultimate goal of endoluminal treatment, but rather provides a window of time for the treatment of foot ulcers. During this window, surgical debridement and other active and effective combination therapy are used to promote ulcer healing; if restenosis or occlusion occurs during this period, endoluminal therapy can be repeated to extend this window of time to achieve therapeutic goals.
Since the correlation between the index of patency after endoluminal treatment of the infrapopliteal artery and its clinical outcome such as limb preservation rate is not significant, and the rate of limb preservation at 3 years after surgery is more than 30% higher than the initial patency rate [12], it is not significant to evaluate the effect of endoluminal treatment only by the imaging performance of patency. The Centre for Cardiac Interventions of the Brescia School of Medicine, Italy, proposes to evaluate the outcome of endoluminal interventions 15 days after the procedure to determine the next treatment option. If the post-treatment increase in transcutaneous partial pressure of oxygen (TcPO2) exceeds 30 mmHg, the wound area decreases, the local skin temperature increases by more than 3°C, and the clinical manifestations, including pain and resolution of skin cyanosis/gangrene, suggest successful revascularization; if not, then reintroduction of intracavitary therapy or amputation in case of deterioration needs to be considered [5]. Several experts from the European Society of Cardiology have also jointly called for standardized criteria for the assessment of chronic ischemia of the lower extremity with intracavitary therapy. After generalizing the baseline condition of the patient, the extent and morphological classification of the lesion, and the specific surgical procedure, the outcome of the treatment should be evaluated and followed up in terms of three major aspects: clinical outcomes, outcomes related to the surgical procedure, and hemodynamic-related indicators [13]. The proposed criteria will facilitate the comparison of treatment outcomes between centers and the further development of multicenter clinical studies.
V. New advances in endoluminal treatment strategies.
The best strategy for endoluminal therapy is to open the occluded vessels and establish a direct arterial blood supply to the foot lesion.
Intraluminal treatment strategies are different in diabetic and non-diabetic patients [5]. In diabetic patients, the incidence of PAD and CLI is significantly higher, and the lesions are characterized by long segmental occlusive lesions of multiple branches and segments of the infrapopliteal artery, severe calcification of the lesion vessels, and poor distal outflow tracts, so the intraluminal treatment of these patients is based on the reconstruction of the infrapopliteal artery. In non-diabetic CLI patients, the lesions are mostly located in the femoral N and iliac arteries, and the reconstruction of the iliofemoral artery should be emphasized in such patients; when the superficial femoral artery is difficult to open, good results can still be obtained by treating the deep femoral artery [5, 14].
In patients with diabetic foot ulcers with CLI, the most common infrapopliteal lesion vessels are the anterior and posterior tibial arteries; the peroneal artery is often the last of the three main infrapopliteal vessels to become diseased [5, 15]. Patients with diabetes mellitus are less capable of reactive vasoproliferation and collateral vessel formation due to ischemia from infrapopliteal artery occlusion, and their collateral vessels are poorly distributed and circulate poorly; even when patients present with a single tibial artery occlusion, they often develop CLI and foot ulcers due to their lack of collateral circulation. The anatomical end of the peroneal artery is located above the ankle and has fewer collateral branches extending to the foot; treating the peroneal artery alone does not provide an effective blood supply to prevent amputation above the ankle [15]; therefore, the anterior and posterior tibial arteries should be opened as much as possible to obtain direct blood flow to the foot in diabetic patients. The anterior and posterior tibial arteries provide blood supply to the toe and heel, respectively, and the vessels supplying the lesion should be opened selectively according to the anatomical characteristics of the vascular distribution of the foot and the different sites of the lesion in clinical practice.
When the opening of the anterior and posterior tibial arteries is difficult, some authors have proposed the new idea of endoluminal angioplasty of the lateral branches of the peroneal artery [16]. Some lateral branches of the distal peroneal artery extend into the small arteries of the foot, and the anterior peroneal artery is connected to the dorsalis pedis artery while the posterior branch communicates with the plantar artery. Usually, the anterior and posterior peroneal arteries are narrowed or occluded. When the anatomic conditions are suitable, balloon dilatation endoluminal angioplasty is technically feasible to establish direct flow to the foot; its clinical outcome remains to be evaluated.
The key to endoluminal treatment of occlusive lesions is the use of guidewires to pass through the occluded lesion and re-enter the true lumen. The application of ipsilateral paracentesis techniques, subintimal techniques, and facilities dedicated to reentry into the true lumen such as the Pioneer or Outback catheters have greatly increased the success rate of treatment of occlusive lesions of the superficial femoral artery. The infrapopliteal artery remains more difficult to treat due to its thin vessels, long occlusive lesions and lack of dedicated facilities. In recent years new materials such as Chronic total occlusion (CTO) specific guidewires, support catheters and balloons have been used to facilitate the passage of occlusive lesions of the inferior femoral artery. There are also new advances in operative techniques.
1. retrograde access techniques [17, 18].
Possible mechanisms for the retrograde passage of guidewires through occlusive lesions: (1) due to hemodynamic effects, the distal end of the occlusive lesion is concave and appears to be a luminal stump, from which the guidewire can be introduced more easily; (2) the composition of the proximal and distal ends of the occlusive lesion is different, with less fibrotic or calcified tissue in the distal lesion than in the proximal end; (3) the proximal end of the vessel is often divided into cephalocaudal to lateral branches, while the occlusive lesion has a different composition. The occluded lesion makes it difficult to keep the proximal end of the vessel in a straight line; the guidewire can easily enter the lateral branches when passing in a downstream direction.
The techniques to constitute a retrograde access include: ① Constructing a pedal-plantar loop: using the anatomical features of the dorsal and plantar arteries, a pedal-plantar loop is formed by passing through the anterior tibial artery, the dorsalis pedis artery, and then retrograde through the plantar artery to the distal posterior tibial artery; conversely, a pedal-plantar loop is formed by passing through the posterior tibial artery, the arch of the plantar artery, and then retrograde through the dorsalis pedis artery to the distal anterior tibial artery. This constitutes a plantar artery loop. Using this plantar artery loop, the guidewire can be passed retrogradely through the occluded lesion to treat occlusive lesions of the tibial artery [19]. (ii) The guidewire is passed through the tibiofibular artery to form a loop (Trans-Collateral), and this loop is used to pass retrogradely through the occluded lesion [18, 20]. This method has only been reported in a single case. (3) The foot vessel (dorsal or posterior tibial artery) is punctured or the skin is incised to expose the vessel underneath the puncture tube, thus establishing a retrograde access. At present, our center has mastered this technique and it is widely used in clinical practice.
2. Dual access technique combining the cascade and retrograde access [21].
Combining the prograde and retrograde access, when the prograde access is blocked through the occluded lesion, retrograde placement of guidewire and catheter can be performed by dorsalis pedis or posterior tibial artery puncture; the prograde and retrograde placed guidewire and catheter serve as markers for each other in the vessel, and the advantages of the retrograde access technique can be used to pass through the occluded lesion or by docking the guidewire and catheter.
In conclusion, endoluminal treatment of arterial occlusive disease of the lower extremities, especially the infrapopliteal artery, has a wide application prospect today due to the safety, effectiveness and reproducibility of its treatment and the continuous improvement of equipment and devices and operational techniques.
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