Acute limb ischaemia | |
---|---|
Other names | Acute limb ischemia |
Acute embolism to the right femoral artery resulting in ischemia | |
Symptoms | Cold, painful, pulseless limb that cannot move |
Causes | Embolism, thrombosis |
Treatment | Thrombectomy, embolectomy, thrombolysis |
Medication | Thrombolytic drugs |
Acute limb ischaemia (ALI) occurs when there is a sudden lack of blood flow to a limb [1] within 14 days of symptoms onset. [2] On the other hand, when the symptoms exceed 14 days, [3] it is called critical limb ischemia (CLI). CLI is the end stage of peripheral vascular disease where there is still some collateral circulation (alternate circulation pathways) that bring some blood flow (although inadequate) to the distal parts of the limbs. [2] While limbs in both acute and chronic limb ischemia may be pulseless, a chronically ischemic limb is typically warm and pink due to a well-developed collateral artery network and does not need emergency intervention to avoid limb loss, whereas ALI is a vascular emergency. [4]
Acute limb ischaemia is usually caused by embolism or thrombosis, or rarely by dissection or trauma. [5] Thrombosis is usually caused by peripheral vascular disease (atherosclerotic disease that leads to blood vessel blockage), while an embolism is usually of cardiac origin. [6] In the United States, ALI is estimated to occur in 14 out of every 100,000 people per year. [7] With proper surgical care, acute limb ischaemia is a highly treatable condition; however, delayed treatment (beyond 6 to 12 hours) can result in permanent disability, amputation, and/or death. Early detection and steps towards fixing the problem with limb-sparing techniques can salvage the limb. Compartment syndrome is an occasional complication that may also occur in acute limb ischaemia because of the biotoxins that accumulate distal to the occlusion resulting in edema. [1]
The New Latin term ischaemia as written, is a British version of the word ischemia, and stems from the Greek terms ischein 'to hold'; and haima 'blood'. [8] In this sense, ischaemia refers to the inhibition of blood flow to/through the limb.
Symptoms of acute limb ischemia can occur anywhere from minutes to days. [2]
The classic symptoms of acute limb ischaemia include:
These symptoms are called "the six P's'"; [9] [10] [11] they are commonly mis-attributed to compartment syndrome.
Symptoms may also include intermittent claudication or pain at rest. In late stages, paresthesia is replaced by anesthesia (numbness) due to death of nerve cells. [12] In severe cases, gangrene can occur suddenly and spread rapidly, [13] and should be treated within six hours of ischaemia. [14]
Embolic occlusions should be considered when patients present with a sudden and severe onset. Acute arterial occlusions may also lead to arterial spasms, causing a "marble" white appearance. [2] Patients who have an embolic cause of ALI often present with unilateral decreased pulses, whereas those with a thrombotic cause of ALI such as atherosclerosis often present with bilateral decreased pulses. [2]
Most acute limb ischemia is caused by thrombosis (40% of the cases), embolism (30%), vascular graft thrombosis (20%), thrombosis by popliteal artery aneurysm (5%), and major trauma (5%). [2]
Risk factors include history of diabetes, coronary artery disease, tobacco use, atrial fibrillation, hypercoagulable disorders, autoimmune diseases, or diseases affecting connective tissues, such as Ehlers-Danlos syndrome. [15] In a patient with otherwise no known risk factors, atrial fibrillation with embolism should be suspected. [15]
Thrombosis occurs when a blood clot forms within an artery, which can result from atherosclerosis or a hypercoagulable state. [16] This leads to an occlusion of the artery and thus ischemia. Unlike embolic causes of limb ischemia, thrombosis is progressive and develops over time. In hypercoagulable states, thrombosis can occur in areas without atherosclerosis, and usually presents in patients with malignancy, hyperviscosity, or low blood flow. [16]
Common sources of emboli leading to arterial occlusions include mural thrombi from the heart or debris from the proximal aorta. As the emboli travel through the peripheral arteries, which are more narrow, the risk of occlusion increases. [16] The arteries most commonly affected by emboli include the common femoral, common iliac, and popliteal artery bifurcations. [17]
Thromboses as a result of cardiac interventions has become increasingly common. Clots may form at the sheath or catheter tip, potentially causing embolism during sheath removal.
Thromboses forming within aneurysms are most frequently seen in the popliteal artery. Acute limb ischemia due to a popliteal artery aneurysm has been reported to have a 20-60% chance of limb loss and 12% mortality rate. [18]
Acute limb ischemia may also be caused by traumatic disruption of blood flow to a limb, which may present with either hard signs or soft signs of vascular injury. [16] Hard signs include pulsatile bleeding, expanding hematoma, or absent distal pulses, and must be taken to surgery emergently. Soft signs include reduced pulses or nerve damage. [16]
Once signs and symptoms of acute limb ischemia are identified, the cause and location of the occlusion and its severity need to be addressed. A clinical pulse examination can be done to detect the location of the occlusion by finding the area where the pulse is detected until the area where the pulse disappears. The skin temperature would also be colder in the pulseless area compared to the areas where the pulses are present. [1]
A Doppler evaluation is often the first imaging choice to diagnose ALI because it is inexpensive, accessible, non-invasive, and can be done in a short amount of time. [2] It is used to show the extent and severity of the ischaemia by showing flow in smaller arteries. An occlusion of the artery would be seen by decreased or absent flow distal to the occlusion. Doppler ultrasound can even distinguish between embolic and thrombotic plaque. The former would show a delineated, round thrombus, whereas the latter would show narrowed arterial lumen with atherosclerotic plaque. [2]
Although Doppler ultrasounds provide excellent information, there may be difficulty in evaluating aortic or iliac arteries in patients who are obese or have significant gas. [2] Other diagnostical tools are duplex ultrasonography, computed tomography angiography (CTA), and magnetic resonance angiography (MRA). The CTA and MRA provide higher-resolution images used in planning revascularization, but they may only be used in patients without a threatened limb due to time constraints. CTA uses radiation and may not pick up on vessels for revascularization that are distal to the occlusion, but it is much quicker than MRA. [1] In treating acute limb ischaemia, timing is everything. [19]
Patients with clinical suspicion of ALI should also receive a chest X-ray and echocardiogram to evaluate for cardiac embolism, cardiac thrombus, myocardial infarction, and cardiac function. [2]
The Rutherford classification scale is the most widely used system to determine prognosis and management strategy. [20]
Category | Description/Prognosis | Findings | Doppler signs | ||
---|---|---|---|---|---|
Sensory Loss | Muscle Weakness | Arterial | Venous | ||
I. Viable | Not immediately threatened | None | None | Audible | Audible |
IIa. Marginally Threatened | Salvageable if promptly treated | Minimal (toes) or none | None | Inaudible | Audible |
IIb. Immediately Threatened | Salvageable with immediate revascularization | More than toes, associated rest pain | Mild or moderate | Inaudible | Audible |
III. Irreversible | Major tissue loss or permanent nerve damage inevitable | Profound, anesthetic | Profound, paralysis | Inaudible | Inaudible |
The primary prevention of acute limb ischemia starts with awareness of peripheral artery disease (PAD). In patients with PAD, smoking cessation, weight control, blood pressure control, diabetes control, physical activity, and rhythm control in those with atrial fibrillation should be encouraged. [21] Medical therapy such as antihypertensives, lipid-lowering therapy, antidiabetic therapy, and antithrombotics can be considered when lifestyle modifications are not enough. Antiplatelets are recommended with 1C level of evidence for patients with symptomatic PAD, with a preference of clopidogrel over aspirin. [21] The VIVA trial demonstrated a 7% reduction in mortality of using ankle-brachial index (ABI), blood pressure management, and ultrasonography for vascular disease screening. [21]
Initial anticoagulation with heparin is usually first recommended to prevent further development of the clot and help reduce ischemia. [1]
The best course of treatment varies from case to case. The physician must take into account the details in the case before deciding on the appropriate treatment. No treatment is effective for every patient. [12]
Treatment depends on many factors, including:
Endovascular interventions for ALI are minimally invasive procedures designed to quickly restore blood flow and avoid more extensive surgery. In endovascular interventions, a catheter is used to deliver medication such as thrombolytics to dissolve the clot. In the past, streptokinase was the main thrombolytic chemical. More recently, drugs such as tissue plasminogen activator, urokinase, and anistreplase have been used in their place. Mechanical methods of injecting the thrombolytic compounds have improved with the introduction of pulsed spray catheters—which allow for a greater opportunity for patients to avoid surgery. [22] [23] Pharmacological thrombolysis requires a catheter to be inserted into the affected area, attached to the catheter is often a wire with holes to allow for a wider dispersal area of the thrombolytic agent. These agents lyse the ischemia-causing thrombus quickly and effectively. [24] However, the efficacy of thrombolytic treatment is limited by hemorrhagic complications. Plasma fibrinogen level has been proposed as a predictor of these hemorrhagic complications. However, based on a systematic review of the available literature until January 2016, the predictive value of plasma is unproven. [25] After the clot has been dissolved or removed, a stent or balloon may be placed to keep the artery open and prevent further ischemia.
Major complications of thrombolysis include intracranial hemorrhage, major bleeding, compartment syndrome, and failure of thrombolysis. [15]
Surgery is often recommended in those with Rutherford Class 2b or greater, as blood flow is generally restored much more quickly. The primary surgical intervention in acute limb ischaemia is emergency embolectomy using a Fogarty Catheter, providing the limb is still viable within the 4-6h timeframe. [26] Other options include a vascular bypass to route blood flow around the clot. [27]
For secondary prevention of ALI, long-term anticoagulation and management of atherosclerosis must be considered. [1]
There is a high risk of mortality and cardiovascular events in those with limb ischemia. At one year, around 20-25% will die and 25-30% will need major amputation. [28]
The major cause of acute limb ischaemia is arterial embolism (80%), while arterial thrombosis is responsible for 20% of cases. In rare instances, arterial aneurysm of the popliteal artery has been found to create a blood clot or embolism resulting in ischaemia. [29]
Thrombosis is the formation of a blood clot inside a blood vessel, obstructing the flow of blood through the circulatory system. When a blood vessel is injured, the body uses platelets (thrombocytes) and fibrin to form a blood clot to prevent blood loss. Even when a blood vessel is not injured, blood clots may form in the body under certain conditions. A clot, or a piece of the clot, that breaks free and begins to travel around the body is known as an embolus.
Interventional radiology (IR) is a medical specialty that performs various minimally-invasive procedures using medical imaging guidance, such as x-ray fluoroscopy, computed tomography, magnetic resonance imaging, or ultrasound. IR performs both diagnostic and therapeutic procedures through very small incisions or body orifices. Diagnostic IR procedures are those intended to help make a diagnosis or guide further medical treatment, and include image-guided biopsy of a tumor or injection of an imaging contrast agent into a hollow structure, such as a blood vessel or a duct. By contrast, therapeutic IR procedures provide direct treatment—they include catheter-based medicine delivery, medical device placement, and angioplasty of narrowed structures.
Peripheral artery disease (PAD) is a vascular disorder that causes abnormal narrowing of arteries other than those that supply the heart or brain. PAD can happen in any blood vessel, but it is more common in the legs than the arms.
Ischemia or ischaemia is a restriction in blood supply to any tissue, muscle group, or organ of the body, causing a shortage of oxygen that is needed for cellular metabolism. Ischemia is generally caused by problems with blood vessels, with resultant damage to or dysfunction of tissue i.e. hypoxia and microvascular dysfunction. It also implies local hypoxia in a part of a body resulting from constriction.
Thrombolysis, also called fibrinolytic therapy, is the breakdown (lysis) of blood clots formed in blood vessels, using medication. It is used in ST elevation myocardial infarction, stroke, and in cases of severe venous thromboembolism.
Vascular surgery is a surgical subspecialty in which vascular diseases involving the arteries, veins, or lymphatic vessels, are managed by medical therapy, minimally-invasive catheter procedures and surgical reconstruction. The specialty evolved from general and cardiovascular surgery where it refined the management of just the vessels, no longer treating the heart or other organs. Modern vascular surgery includes open surgery techniques, endovascular techniques and medical management of vascular diseases - unlike the parent specialities. The vascular surgeon is trained in the diagnosis and management of diseases affecting all parts of the vascular system excluding the coronaries and intracranial vasculature. Vascular surgeons also are called to assist other physicians to carry out surgery near vessels, or to salvage vascular injuries that include hemorrhage control, dissection, occlusion or simply for safe exposure of vascular structures.
Intermittent claudication, also known as vascular claudication, is a symptom that describes muscle pain on mild exertion, classically in the calf muscle, which occurs during exercise, such as walking, and is relieved by a short period of rest. It is classically associated with early-stage peripheral artery disease, and can progress to critical limb ischemia unless treated or risk factors are modified and maintained.
A vascular bypass is a surgical procedure performed to redirect blood flow from one area to another by reconnecting blood vessels. Often, this is done to bypass around a diseased artery, from an area of normal blood flow to another relatively normal area. It is commonly performed due to inadequate blood flow (ischemia) caused by atherosclerosis, as a part of organ transplantation, or for vascular access in hemodialysis. In general, someone's own vein (autograft) is the preferred graft material for a vascular bypass, but other types of grafts such as polytetrafluoroethylene (Teflon), polyethylene terephthalate (Dacron), or a different person's vein (allograft) are also commonly used. Arteries can also serve as vascular grafts. A surgeon sews the graft to the source and target vessels by hand using surgical suture, creating a surgical anastomosis.
An embolus, is described as a free-floating mass, located inside blood vessels that can travel from one site in the blood stream to another. An embolus can be made up of solid, liquid, or gas. Once these masses get "stuck" in a different blood vessel, it is then known as an "embolism." An embolism can cause ischemia—damage to an organ from lack of oxygen. A paradoxical embolism is a specific type of embolism in which the embolus travels from the right side of the heart to the left side of the heart and lodges itself in a blood vessel known as an artery. Thus, it is termed "paradoxical" because the embolus lands in an artery, rather than a vein.
Intestinal ischemia is a medical condition in which injury to the large or small intestine occurs due to not enough blood supply. It can come on suddenly, known as acute intestinal ischemia, or gradually, known as chronic intestinal ischemia. The acute form of the disease often presents with sudden severe abdominal pain and is associated with a high risk of death. The chronic form typically presents more gradually with abdominal pain after eating, unintentional weight loss, vomiting, and fear of eating.
Embolectomy is the emergency interventional or surgical removal of emboli which are blocking blood circulation. It usually involves removal of thrombi, and is then referred to as thromboembolectomy or thrombectomy. Embolectomy is an emergency procedure often as the last resort because permanent occlusion of a significant blood flow to an organ leads to necrosis. Other involved therapeutic options are anticoagulation and thrombolysis.
Arterial embolism is a sudden interruption of blood flow to an organ or body part due to an embolus adhering to the wall of an artery blocking the flow of blood, the major type of embolus being a blood clot (thromboembolism). Sometimes, pulmonary embolism is classified as arterial embolism as well, in the sense that the clot follows the pulmonary artery carrying deoxygenated blood away from the heart. However, pulmonary embolism is generally classified as a form of venous embolism, because the embolus forms in veins. Arterial embolism is the major cause of infarction.
A limb infarction is an area of tissue death of an arm or leg. It may cause skeletal muscle infarction, avascular necrosis of bones, or necrosis of a part of or an entire limb.
Blood clots are a relatively common occurrence in the general population and are seen in approximately 1-2% of the population by age 60. Typically, blood clots develop in the deep veins of the lower extremities, deep vein thrombosis (DVT) or as a blood clot in the lung, pulmonary embolism. A very small number of people who develop blood clots have a more serious and often life-threatening condition, known as thrombotic storm (TS). TS is characterized by the development of more than one blood clot in a short period of time. These clots often occur in multiple and sometimes unusual locations in the body and are often difficult to treat. TS may be associated with an existing condition or situation that predisposes a person to blood clots, such as injury, infection, or pregnancy. In many cases, a risk assessment will identify interventions that will prevent the formation of blood clots.
Percutaneous intentional extraluminal revascularization is a percutaneous technique used in interventional radiology for limb salvage in patients with lower limb ischemia due to long superficial femoral artery occlusions. This method is intended for those patients who make poor candidates for infrainguinal arterial bypass surgery. A guide wire is intentionally introduced in the subintimal space, after which balloon dilatation is performed to create a new lumen for the blood to flow through. The technique is not without complications but may serve as a "temporary bypass" to provide wound healing and limb salvage.
Chronic limb threatening ischemia (CLTI), also known as critical limb ischemia (CLI), is an advanced stage of peripheral artery disease (PAD). It is defined as ischemic rest pain, arterial insufficiency ulcers, and gangrene. The latter two conditions are jointly referred to as tissue loss, reflecting the development of surface damage to the limb tissue due to the most severe stage of ischemia. Compared to the other manifestation of PAD, intermittent claudication, CLI has a negative prognosis within a year after the initial diagnosis, with 1-year amputation rates of approximately 12% and mortality of 50% at 5 years and 70% at 10 years.
Blood vessel disorder generally refers to the narrowing, hardening or enlargement of arteries and veins. It is often due to the build-up of fatty deposits in the lumen of blood vessels or infection of the vessel wall. This can occur in various locations such as coronary blood vessels, peripheral arteries and veins. The narrowed arteries would block the blood supply to different organs and tissues. In severe conditions, it may develop into more critical health problems like myocardial infarction, stroke or heart failure, which are some of the major reasons of death.
Popliteal bypass surgery, more commonly known as femoropopliteal bypass or more generally as lower extremity bypass surgery, is a surgical procedure used to treat diseased leg arteries above or below the knee. It is used as a medical intervention to salvage limbs that are at risk of amputation and to improve walking ability in people with severe intermittent claudication and ischemic rest pain.
Arterial occlusion is a condition involving partial or complete blockage of blood flow through an artery. Arteries are blood vessels that carry oxygenated blood to body tissues. An occlusion of arteries disrupts oxygen and blood supply to tissues, leading to ischemia. Depending on the extent of ischemia, symptoms of arterial occlusion range from simple soreness and pain that can be relieved with rest, to a lack of sensation or paralysis that could require amputation.