Myocardial Infarction with Left Ventricular Aneurysm (see Left Ventricular Aneurysm, [[Left Ventricular Aneurysm]]): usually antero-apical with associated decreased systolic function
Left Ventricular Dysfunction/Cardiomyopathy with Decreased Cardiac Output (see Congestive Heart Failure, [[Congestive Heart Failure]])
Mechanical Prosthetic Mitral/Aortic Valve: usually in the setting of inadequate anticoagulation
Mitral Annular Calcification
Papillary Fibroelastoma: cardiac tumor usually found on the mitral/aortic valves
Arterial Source: account for 20% of arterial emboli
Aortic Atherosclerotic Plaque: risk of embolization is increased with increased plaque thickness, plaque ulceration or mobility, and cardiovascular procedures (cardiac catheterization/intra-aortic balloon pump/cardiac surgery may dislodge the plaque)
Paradoxical Embolism: account for 2-4% of arterial emboli
Epidemiology
Patients with paradoxical embolization are typically younger (mean age: 39) than patients with other types of arterial thromboembolization (mean age: 68)
Patients with paradoxical embolization typically have little evidence of cardiac or peripheral arterial disease
Mechanism: venous thrombosis that traverses a right-to-left intracardiac shunt (patent foramen ovale, atrial septal defect, atrial septal aneurysm)
Venous Sources
Upper/Lower Extremity Deep Venous Thrombosis (DVT)
Destination of Arterial Embolism
General Comments
Lower extremities are affected more commonly than upper extremities
Emboli commonly lodge in sites of arterial narrowing: at atherosclerotic plaques or bifurcation points (common femoral bifurcation, common iliac bifurcation, popliteal artery bifurcation)
Femoral Artery: 28% of cases
Upper Extremity Artery: 20% of cases
Aortoiliac: 18% of cases
Popliteal Artery: 17% of cases
Visceral Artery: 9% of cases
Other Artery: 9% of cases
Arterial Thrombosis
General Comments
Arterial thrombosis usually occurs at the site of an atherosclerotic plaque, in arterial aneurysms, at the site or within a prior revascularization (stents, grafts), or in a vein bypass (usually at a site of venous abnormality)
Atherosclerotic Plaque: the degree of limb ischemia in a patient with pre-existing atherosclerotic plaques in the affected distribution may be less severe, due to the prior development of collateral circulation
Cardiac Catheterization: incidence of arterial complications following cardiac catheterization (hematoma, pseudoaneurysm, arteriovenous fistula, arterial occlusion, cholesterol emboli syndrome) is between 1.5-9%
Arterial occlusions can occur due to intimal flaps/dissections or embolization of thrombus from the arterial sheath site
Arteriolar/Arterial Compression Due to Compartment Syndrome (see Compartment Syndrome, [[Compartment Syndrome]])
Phlegmasia Cerulea Dolens (see Deep Venous Thrombosis, [[Deep Venous Thrombosis]]): acute massive venous thrombosis with obstructed venous drainage of lower extremity -> may result in arterial compression and acute limb ischemia
Any Other Etiology of Compartment Syndrome
Physiology
Acute Arterial Occlusion: with a sudden decrease in limb perfusion that results in a potential threat to limb viability
Atheroemboli vs Thromboemboli
Compared to thromboemboli, atheroemboli are much less likely to produce acute limb ischemia, more commonly resulting in small vessel occlusion with features such as digital ischemia and livedo reticularis (see Cholesterol Emboli Syndrome, [[Cholesterol Emboli Syndrome]])
Diagnosis
Trans-Thoracic Echocardiogram (TTE): useful as the first study to identify cardiac sources of arterial emboli
Trans-Esophageal Echocardiogram (TEE): useful to identify cardiac sources of arterial emboli in cases where trans-thoracic echocardiogram is inconclusive or poor quality
Ankle-Brachial Index (ABI): value <0.4 indicates significant ischemia
Angiogram with Digital Subtraction Angiography: diagnostic
Features which allow differentiation between embolism and thrombosis
Embolism: sharp cutoff with rounded reverse meniscus sign, intraluminal filling defect, presence of multiple filling defects, absence of collateral circulation
Thrombosis: sharp or tapered (but not rounded) cutoff, diffuse atherosclerosis with collateral circulation
Clinical Classification of Acute Limb Ischemia
Viable
Mild Pain
Intact Capillary Refill
No Motor Deficit
No Sensory Deficit
Audible Arterial Doppler
Audible Venous Dopplers
Threatened
Severe Pain
Delayed Capillary Refill
Partial Motor Deficit
Partial Sensory Deficit
Inaudible Arterial Doppler
Audible Venous Dopplers
Non-Viable
Variable Pain
Absent Capillary Refill
Complete Motor Deficit
Complete Sensory Deficit
Inaudible Arterial Doppler
Inaudible Venous Dopplers
Clinical Manifestations
General Comments
Patient with Underlying Peripheral Arterial Disease: symptoms may develop acutely or subacutely (even presenting with gradual progression of symptoms in some cases)
Patient without Underlying Peripheral Arterial Disease: typically present acutely with classical presentation of 6 P‘s
Usually distal in the lower extremity and progresses proximally with increased duration of ischemia
Usually gradually increases in severity: however, later in course, pain may decrease due to ischemic sensory loss
In contrast, acute compartment syndrome must be ruled out as the etiology of extremity pain (it usually manifests with leg swelling and leg pain elicited by passive stretch or palpation of the muscles) (see Compartment Syndrome, [[Compartment Syndrome]])
Parasthesias/Anesthesia (see Parasthesias, [[Parasthesias]] and Anesthesia, [[Anesthesia]])
The anterior compartment of the lower leg is most sensitive to ischemia: sensory deficits over the dorsal foot are an early sign of acute vascular insufficiency
Anesthesia occurs late in the course
Motor Weakness/Paralysis (see Weakness, [[Weakness]] and Paralysis, [[Paralysis]])
Motor weakness may occur earlier in the course
Paralysis occurs late in the course
Ischemic Ulcers (see Mucocutaneous Ulcers, [[Mucocutaneous Ulcers]]): presence usually indicates chronic vascular insufficiency
Gangrene (see Gangrene, [[Gangrene]]): occurs late in course
Pallor: pale skin
The point of arterial occlusion is usually one joint above the line of demarcation between the normal and ischemic tissue
Polikilothermia: cool skin
Poor Skin Perfusion: poor capillary refill
Pulselessness: handheld Dopplers may be required to assess arterial flow in the lower extremities
Rhabdomyolysis/Compartment Syndrome (see Rhabdomyolysis, [[Rhabdomyolysis]] and Compartment Syndrome, [[Compartment Syndrome]]): occurs late in course
Treatment Based Upon Clinical Classification
Viable
Urgent Diagnostic Work-Up
Duplex Ultrasound
CT Angiogram
MR Angiogram
Angiogram with Digital Subtraction Angiography
Anticoagulation: indicated early (usually before diagnostic procedures are performed)
