Missile embolus

Definition

Missle Embolization is an umbrella term encompassing the intravasculature and intracardiac embolization of bullet fragments, pellets, and shrapnel most commonly from war related penetrating traumas (mortars, grenades, mines, etc.).

Background

Missile Embolization is a rare phenomenon with the majority of cases occurring in war/combat penetrating trauma, although civilian cases have been reported . While there are several case reviews available in the current literature, definitive recommendations regarding management and treatment are varied. However, a review of the literature reveals a commonly used algorithm for clinical recognition, diagnostic evaluation, and management/treatment of patients with missile embolization .

Recognition

The emergency medicine physician should have a high incidence of suspicion for any patient with penetrating trauma as up to 5% of arterial injuries may be missed on the initial CT angiogram in patients with fragmentation wounds . Commonly, patients present with asymmetric peripheral pulses, evidence of metallic fragments remote from the site of penetrating injury (outside of the expected fragment trajectory), and lack of an exit wound . However patient presentation can vary, and hemodynamically stable vital signs, lack of penetrating trauma on a pulseless extremity, and the presence of an exit wound should not be used to exclude the diagnosis.

As delayed and occult arterial injury have been reported in the literature, patients should be monitored for changing vital signs and/or evidence of traveling retained fragments on serial imaging.

Diagnostic Evaulation

As the majority of patients with penetrating trauma receive initial radiographic imaging (including a eFAST exam), the physician can begin by looking for evidence of metallic foreign bodies both near and far from the site of penetrating injury. If clinically indicated, a chest xray should be obtained as missiles within the systemic venous circulation carry the risk of embolizing to the pulmonary artery.

After initial chest xrays are obtained, further imaging is guided by the location of the suspected missile fragment. If there is evidence of intracardiac or intrapulmonary foreign bodies, a CT chest/abdomen/pelvis with IV contrast is helpful in determining missile trajectory, size, and exact location. A 2D transesophageal echocardiogram is also recommended for intrathoracic missiles . If there is evidence of extremity foreign body (especially with diminished or absent pulses), a CT angiogram of the involved extremity is necessary to guide further surgical management.

Complications of Retained Missile Emboli

Arterial Missile Emboli Complications :

• Distal ischemia
• Thrombosis
• Further embolization.

Venous Missile Emboli Complications:

• Pulmonary artery embolism
• Cardiac valve dysfunction
• Endocarditis
• Abscess formation
• Sepsis
• Thrombosis
• Dysrhythmias
• Intraventricular communications
• Conduction defects
• Tissue erosion
• Hemorrhage
• Cardiac ischemia from erosion into coronary vessels
• Thrombophlebitis

Psychiatric Complications:

• Anxiety
• Cardiac neurosis
• Fear of movement resulting in a dislodgment of the missile from its current location

Management and Treatment

Most authors recommend the removal of symptomatic missile emboli. However, since missile emboli can become dislodged as well as lead to other complications carrying high morbidity and mortality, they are commonly removed. Surgical management is case specific, but minimally invasive embolectomies are preferred if there is a high probability of missile retrieval . There is not strong evidence supporting prophylactic antibiotic use. However, patients with intracardiac emboli may benefit from 48 hours of a first generation cephalosporin to prevent endocarditis with the addition of an aminoglycoside for soft tissue cavitating injuries. Patients with retained missiles who are not surgical candidates maybe benefit from 12 months of anticoagulation .

One literature review recommends the following algorithm for missile emboli based on location :

Algorithm for Management of Missile Emboli based on Anatomic Location

Pitfalls in Management and Treatment

Common pitfalls in the management and treatment of missile emboli involve delayed recognition; dislodgement of the missile during central venous catheter placements, and/or inferior vena cava filters; and repeated emobolization with patient reposition and surgical manipulation.