ALI occurs suddenly and rapidly, and if not treated timely and effectively, limb necrosis may occur within a few days, even threatening patients’ lives. It is not difficult to make a diagnosis based on an acute medical history and clinical symptoms. The preoperative CTA examination is more helpful to clarify the characteristics of the lesion, such as the length and range of the thrombus, with or without atherosclerosis, aneurysm, or dissection. In this study, the etiologies of the patients were mostly as follows: i) acute lower limb arterial embolization, which was caused by the cardiogenic thrombus due to arrhythmia or atrial fibrillation, aortic mural thrombus, or aneurysm thrombus; ii) acute lower limb arterial thrombosis, which was caused by the segmental arterial stenosis and occlusion, arteritis, or hypercoagulable status due to polycythemia vera and thrombocytopenia; iii) arterial dissection, which was caused by the increased compression of the arterial false lumen to the arterial true lumen, or the cover of a limb artery by the intima translocation. Thus, the treatments for ALI should be different according to its different etiologies.
In 1963, Fogarty invented the thrombectomy catheter , which created a new situation of surgical thrombectomy for ALI, especially for arterial embolism. The arterial thrombectomy via the thrombectomy catheter has been continued to this day, while its disadvantage is the high incidence of I/R injury. The CDT is also an effective treatment for ALI [10, 11]. Due to the relatively slow recovery of blood supply, the incidence of I/R injury after CDT is low. CDT is not the first choice for patients at stage IIb with arterial embolization, in particular for patients with long onset time, since their embolus are mostly white thrombus which is difficult to be dissolved. Besides, CDT is not the first choice for patients with polycythemia vera, because it can prolong the ischemia of the affected limb and cause irreversible injury. The thrombectomy is recommended for the preferred choice for ALI patients without aortic dissection. In the current study, the blood supply of the affected limb of 77.1% of patients in Group A was recovered after the primary surgery, suggesting the effectiveness of arterial thrombectomy. Nevertheless, the limitation of simple thrombectomy is that the success criterion is considered as a good blood returning from the distal artery and a good blood spraying from the proximal artery. However, it is impossible to accurately determine whether the blood flow between the proximal and distal artery is improved, or whether the artery is narrowed or injured . In this study, there were 3 main reasons for 20% of patients in Group A whose blood supply did not recover after the primary surgery and underwent a second intervention. The first reason was that thrombectomy resulted in the injury of the arterial intima and the formation of flow-limiting dissection (Fig. 1), which was mostly seen in patients with local segment artery stenosis, excessive balloon pressure of thrombectomy, or repeated thrombectomy. The second reason was that the main artery thrombus was not totally removed, and there were branch arteries supplying blood above the embolized segment. The most cases were that the thrombectomy tubes entered the branch or penetrated the artery wall, failing to reach the far segment of the main artery. Besides, there were also some cases with incomplete thrombectomy due to arteriosclerosis and stenosis. The third reason was that the blocked distal outflow tract caused by unsuccessful thrombectomy, most of which were due to the thrombectomy tube failing to pass the superficial femoral and popliteal arteries to the inferior genicular artery. For those who have undergone the failed arterial thrombectomy, the second intervention under DSA was recommended instead of the second thrombectomy, since most of the detachable thrombus can be removed in the primary thrombectomy and the secondary thrombus formation was prevented by the postoperative anticoagulation. The second thrombectomy could not solve this problem, but increased the injury caused by thrombectomy. In the present study, among these patients underwent second intervention in Group A, 6 cases were the iatrogenic injury with limiting-flow dissection formation, and the thrombus was removed after the stent implantation; 3 cases had the latent arterial stenosis with residual thrombectomy and were relieved by balloon dilatation and stent placement 1 day after thrombolysis with catheterization (Fig. 2). The selective thrombectomy was performed under V18 guidewire fluoroscopy for those patients who were diagnosed with the blocked outflow tract that caused by thrombosis in the lower three branches of the knee using DSA (Fig. 3).
The intraoperative concomitant angiography can determine the characteristics of the lesion, the length of the thrombus segment, with or without arteriosclerosis, stenosis, occlusion, aneurysm, or arterial dissection. The twisted and narrow arterial segment can be selectively passed under the guidance of the guidewire, to avoid injury of the aorta wall and branch arteries caused by embolization catheter. For the thrombosis of the three branches of the lower knee, it can also be selectively cleared, greatly improving the outflow tract. The routine arteriography after thrombectomy is helpful to improve the success rate of operation and to discover the thrombus clearance, the filling of the proximal and the distal arterial lumen, the velocity of blood flow, and the presence or absence of latent arterial stenosis or the secondary iatrogenic injury of the arterial intima [13, 14]. Once diagnosed (Fig. 4), these conditions can be managed timely, significantly reducing the failure rate of operations. Compared with the single cavity tube, the disadvantages of double-cavity thrombectomy tube for thrombectomy under intervention include the larger resistance for balloon filling, the slower regulation of balloon size and pressure, and the poor operating flexibility. During the operation, the filling pressure should be controlled according to the pulling resistance and the balloon size under fluoroscopy. The thrombus cannot be removed if the balloon is too small, while the intima will be injured if the balloon is too large. Especially, when the balloon entered the popliteal artery from the tibial artery, the catheter should be retracted slowly after the balloon filling was adjusted with a short pause under fluoroscopy to avoid residual thrombosis. The presence or absence of stenosis can be determined according to the morphology and resistance of balloons when the catheters were retracted under fluoroscopy. The size of the balloon should be adjusted timely in case of stenosis to avoid the formation of dissection caused by the intimal injury. If the angiography revealed that the arterial stenosis was > 50%, balloon dilatation and stent placement should be performed simultaneously. Thrombus shedding in limb aneurysms is a common cause of recurrent ALI. The presence of proximal aneurysm should be considered in patients with non-arrhythmia and lower limb arterial embolization. In this study, there was one patient with popliteal aneurysms who had a history of lower limb ischemia and thrombolysis for several times. The covered stent Viabahn and thrombectomy were performed on this patient in the same period to isolate tumors and no recurrence was occurred in the follow-up for up to 3 years. For the patients with lower limb ischemia caused by aortic dissection, the key to the success of the operation is the intra-lumen repair of arterial dissection and the recovery of true lumen blood supply. Most of the patients with thrombectomy failure and postoperative death were owing to that the AD was not confirmed before the operation. Patients with ALI were combined with basic diseases in this study. There was no significant difference in the death rate between Group A and B within 30 d after the operation.