ARTERIAL EMBOLUS AND THROMBOSIS

ARTERIAL EMBOLUS AND THROMBOSIS - Jeremy Golding, MD
BASICS
DESCRIPTION
• Acute loss of perfusion distal to occlusion of major artery owing to
- Embolus that migrates to point of occlusion or
- Clot intrinsic to point of occlusion (thrombosis)
• Both are true emergencies.
• Following obstruction of artery, soft coagulum forms both proximally and distally in areas of stagnant flow.
• As clot extends, collateral pathways become involved, and process becomes self-propagating.
• Ultimately, venous circulation can become involved.
• Extent of vascular compromise is critical and determines "golden" period of 4-6 hours. After this time, the profound ischemia leads to irreversible cellular death.
• Distribution of emboli
- Femoral artery: 30%
- Iliac artery: 15%
- Aortic bifurcation: 10%
- Popliteal artery: 10%
- Brachial: 10%
- Mesenteric arteries: 5%
- Renal: 5%
- Cerebral (estimated): 15-20%
• System(s) Affected: Cardiovascular; Hematologic/lymphatic/immunologic
GENERAL PREVENTION
• Anticoagulation in atrial arrhythmia
• Reduction of atherosclerosis risk factors
EPIDEMIOLOGY
• 50-100/100,000 hospital admissions
• A leading cause of limb loss in elderly
• Predominant age: Elderly
• Predominant sex: Male > Female
• Rare in children and during pregnancy
RISK FACTORS
Drug abuse
Genetics
Can be associated with inheritable hypercoagulable and premature atherosclerotic syndromes
ETIOLOGY
• Emboli
• Cardiac
- Atrial flutter/fibrillation
- Valve disease
- Myocardial infarction
- Cardiomyopathy
- Cardiac tumors
- Endocarditis
• Aneurysms: Cardiac, aortic, peripheral
• Thrombosis
- Atherosclerotic occlusive disease
- Aortic and peripheral aneurysms, especially popliteal
- Hypercoagulable states
- Venous gangrene
- Drug abuse
- Heparin allergy (heparin-induced thrombocytopenia)
- Vascular bypass
• Trauma
- Blunt
- Penetrating
- Vascular and cardiac interventional procedures
• Venous thrombosis with patent foramen ovale (paradoxical embolus)
ASSOCIATED CONDITIONS
• Acute mesenteric ischemia
• Renal infarction
• Carotid/cerebrovascular accident
• Multiple emboli
• Digital microembolization


DIAGNOSIS
SIGNS AND SYMPTOMS
• To estimate occlusion location
- Symptoms typically start 1 joint below occlusion.
- Palpable pulses absent below occlusion and accentuated above.
• The 5 Ps: If any one is present, frequent re-evaluations indicated. Proximal occlusions lead to more rapid progression of findings. Occlusion at aortic bifurcation can produce bilateral findings.
- Pain: Diffuse in distal area. If persists, crescendo in nature. Predominates as 1st symptom in embolism. Not alleviated by change of position.
- Pulselessness: Mandatory for diagnosis of embolism or thrombosis. Pedal pulses subject to observer error. Always compare to opposite limb.
- Pallor: Skin color pale early, cyanotic later. Check extremity temperature left to right and top to bottom. Look for signs of chronic ischemia: skin atrophy, loss of hair, thick nails.
- Paresthesia: Numbness early with thrombosis. Light touch 1st to be lost. Not reliable in diabetics. Loss of pain and pressure indicate advanced ischemia.
- Paralysis: Motor defect occurs after sensory and indicates profound ischemia.
TESTS
• EKG
• Special tests
• Noninvasive/indirect
- Doppler: Presence or absence of flow
- Ankle/arm index (AAI; aka ankle/brachial index [ABI]) = dorsal pedal/posterior tibial pressure divided by brachial pressure;
- AAI >0.30 favorable (normal >1)
Lab
For preoperative evaluation, elucidation of cause, or documentation of ischemia severity
• Myocardial/muscle isoenzymes
• Coagulation parameters
• Blood pH/bicarbonate
• Urine myoglobin
• Electrolytes
Imaging
Noninvasive/direct: Duplex imaging if time permits
Diagnostic Procedures/Surgery
Arteriography
• Rarely indicated preoperatively in threatened limb
• May help differentiate thrombosis from embolus in nonthreatened limb
• Useful with occluded grafts
DIFFERENTIAL DIAGNOSIS
• Emboli vs. thrombosis
• Emboli
- Myocardial diseases: Myocardial infarction, arrhythmias (e.g., atrial fibrillation), aneurysms
- Pain as 1st symptom
• Thrombosis
- Absence of heart disease: Infarction, arrhythmias
- Chronic vascular history
- Bilateral changes of chronic ischemia
- Numbness rather than pain as 1st symptom
- Vascular procedures: Bypass/interventional
• Other conditions
- Acute aortic dissection (chest or back pain)
- Acute deep vein thrombosis (massive swelling and warm skin)
- Low flow states
TREATMENT
GENERAL MEASURES
• Time is of the essence.
- Unless contraindicated, systemic heparinization to decrease clot propagation and prophylaxis against further emboli
- Resuscitation and stabilization of patient to extent permitted by time
- Triage, based on detailed exam, history, and Doppler examination, determines appropriate therapy.
• Early subcritical stenosis criteria
- Mild ischemic pain
- Normal neurologic exam
- Capillary refill present
- Arterial signals present by Doppler in distal extremity
- Ankle/arm index >0.30
- Treatment
 Heparin (see "Medications")
 Arteriography
- Embolism
 Surgical removal if acceptable operative risk, for example, balloon embolectomy
 Anticoagulation versus intra-arterial thrombolytics if prohibitive risk
- Thrombosis
 Trial of thrombolytics and correction of arterial defect if good risk
 Anticoagulation if poor risk or thrombolytics contraindicated
• Critical stenosis criteria
- Ischemic pain
- Mild neurologic deficit
- Weakness of dorsiflexion
- Minimal sensory loss: Light touch and/or vibratory
- No pulsatile flow by Doppler
- Venous flow present
- Treatment
 Time to intervention is critical
 Heparin (see "Medications")
 Arteriography
 Individualize thrombolysis and/or operative procedure (depending on extent of thrombosis and amenability for surgical removal)
 Thrombolysis to optimize alternatives
 Adjunctive operative therapy
 Intraoperative lytic therapy: Bypass, patch angioplasty
• Late (nonsalvageable) criteria
- Profound sensory loss
- Muscle paralysis
- Absent capillary refill
- Skin marbling
- Muscle rigor
- No arterial or venous signals by Doppler
- Treatment
 Arteriography usually not warranted
 Attempts at reperfusion contraindicated
 Anticoagulation
 Definitive amputation, if possible
MEDICATION (DRUGS)
First Line
• Heparin
- 80-100 U/kg IV loading dose (~5,000-10,000 U)
- Continuous infusion sufficient to double PTT, generally 18 U/kg/h
• Contraindications
- Heparin:
 Allergy
 Bleeding diathesis
 Trauma (e.g., head injury)
 Hematuria/hemoptysis
 Acute aortic dissection
- tPA/Urokinase
 Nonsalvageable ischemia
 Recent MI
 Aneurysm
 Aortic dissection
 Trauma
 Uncontrolled hypertension
 Recent operative procedure
Second Line
Multiple thrombolytics in development
SURGERY
Angioplasty, Thromboembolectomy
FOLLOW-UP
PROGNOSIS
• 90% good outcome with prompt treatment
• Delayed/untreated associated with high mortality and limb loss
• 20-30% hospital mortality associated with causative factors
COMPLICATIONS
• Acidosis
• Myoglobinuria and acute renal failure
• Hyperkalemia
• Recurrent occlusion
• Failure to remove clot/obstruction
• Compartment syndromes/reperfusion syndrome, delayed or acute: Predisposing factors include
- Combined arterial injury
- Profound and prolonged ischemia
- Hypotension
• Clinical findings of compartment syndrome
- Severe pain
- Pain with passive muscle movement
- Hypesthesias of nerves in compartment
- Paralysis of nerves, especially peroneal foot drop
- Tender, tense edema
- Compartment pressure >30-45 mm Hg
• Consequences of unrecognized compartment syndrome
- Acute
 Amputation
 Sepsis
 Myoglobin renal failure
 Shock
 Multiple organ failure
- Delayed
 Ischemic contracture
 Infection
 Causalgia
 Gangrene
• Treatment of compartment syndrome is fasciotomy.
PATIENT MONITORING
Postoperative monitoring
• Anticoagulation
• Establish brisk diuresis.
• Continued resuscitation and diagnosis, including echocardiography and other studies (see "Causes" and "Risk Factors")
• Monitor perfusion stability.
• Treat/eliminate causative factors.
REFERENCES
1. Antithrombotic therapy in peripheral arterial occlusive disease: the Seventh ACCP Conference on Antithrombotic and Thrombolytic Therapy. Chest.2004 Sep;126(3 Suppl):609S-26S. Available at www.ngc.gov.
2. Townsend. Sabiston Textbook of Surgery, 17th ed. Boston: Saunders, 2004.
3. Brewster DC, Chin AK, Fogarty TJ. Arterial thrombosis. In: Rutherford RB, ed. Vascular Surgery, 3rd ed. Philadelphia: WB Saunders; 1989.
4. Miller DC, Roon AJ, eds. Diagnosis and Management of Peripheral Vascular Diseases. Menlo Park, CA: Addison-Wesley; 1982.
5. Rutherford RB, Flannigan DP, Gupta SK, et al. Suggested standards of reports dealing with lower extremity ischemia. J Vasc Surg. 1986;64:80-94.