Use of AngioJet mechanical thrombectomy for acute peripheral ischemia associated with stent fracture

Acute on chronic limb ischemia: From surgical embolectomy and thrombolysis to endovascular options

After the invention of the balloon catheter by Fogarty in 1963, surgical thromboembolectomy was considered the gold standard treatment for many years in patients with acute lower limb ischemia (ALLI). ALLI is a dramatic event, carrying a high risk of amputation and perioperative morbidity and mortality. The evolution of endovascular technologies has resulted in a variety of therapeutic options to establish arterial patency. In the 1970s, Dotter first introduced the idea of clot lysis in the treatment of ALLI, which was modified to catheter-directed thrombolysis, and now clot aspiration techniques. Currently, the majority of ALLI (about 70%) is arterial thrombosis, which generally occurs in the setting of preexisting vascular lesion. This condition is very common in patients with diabetes. Clinical presentation in case of thrombosis on atherosclerotic stenosis (so called "acute on chronic ischemia") may be less severe, but treatment is generally more challenging than ALLI due to embolism, considering the complexity in device trackability through the diseased vessels, potential vessel injury, incomplete revascularization, and need of correction of underlying vascular lesions. Although surgery is still a treatment option, especially for ALLI, endovascular interventions have assumed a prominent role in restoring limb perfusion. In this review, the treatment options for ALLI are detailed from surgical thromboembolectomy to thrombolysis and current endovascular techniques, including mechanical fragmentation, rheolytic thrombectomy, and aspiration thrombectomy. The evolution to endovascular therapies has resulted in improved clinical outcomes and lower rates of morbidity.

Acute Limb Ischemia-Much More Than Just a Lack of Oxygen

Acute ischemia of an extremity occurs in several stages, a lack of oxygen being the primary contributor of the event. Although underlying patho-mechanisms are similar, it is important to determine whether it is an acute or chronic event. Healthy tissue does not contain enlarged collaterals, which are formed in chronically malperfused tissue and can maintain a minimum supply despite occlusion. The underlying processes for enhanced collateral blood flow are sprouting vessels from pre-existing vessels (via angiogenesis) and a lumen extension of arterioles (via arteriogenesis). While disturbed flow patterns with associated local low shear stress upregulate angiogenesis promoting genes, elevated shear stress may trigger arteriogenesis due to increased blood volume. In case of an acute ischemia, especially during the reperfusion phase, fluid transfer occurs into the tissue while the vascular bed is simultaneously reduced and no longer reacts to vaso-relaxing factors such as nitric oxide. This process results in an exacerbative cycle, in which increased peripheral resistance leads to an additional lack of oxygen. This whole process is accompanied by an inundation of inflammatory cells, which amplify the inflammatory response by cytokine release. However, an extremity is an individual-specific composition of different tissues, so these processes may vary dramatically between patients. The image is more uniform when broken down to the single cell stage. Because each cell is dependent on energy produced from aerobic respiration, an event of acute hypoxia can be a life-threatening situation. Aerobic processes responsible for yielding adenosine triphosphate (ATP), such as the electron transport chain and oxidative phosphorylation in the mitochondria, suffer first, thus disrupting the integrity of cellular respiration. One consequence of this is irreparable damage of the cell membrane due to an imbalance of electrolytes. The eventual increase in net fluid influx associated with a decrease in intracellular pH is considered an end-stage event. Due to the lack of ATP, individual cell organelles can no longer sustain their activity, thus initiating the cascade pathways of apoptosis via the release of cytokines such as the BCL2 associated X protein (BAX). As ischemia may lead to direct necrosis, inflammatory processes are further aggravated. In the case of reperfusion, the flow of nascent oxygen will cause additional damage to the cell, further initiating apoptosis in additional surrounding cells. In particular, free oxygen radicals are formed, causing severe damage to cell membranes and desoxyribonucleic acid (DNA). However, the increased tissue stress caused by this process may be transient, as radical scavengers may attenuate the damage. Taking the above into final consideration, it is clearly elucidated that acute ischemia and subsequent reperfusion is a process that leads to acute tissue damage combined with end-organ loss of function, a condition that is difficult to counteract.