Depending on the location of the foreign bodies in the circulation, they can be broadly classified as follows:

Foreign bodies in the venous circulation:

Foreign bodies in the arterial circulation:

The retrieval decision is individualized, depending on the merits and the risks involved in each case. The localization and size of the foreign body is one of the main factors to be considered with regard to the necessity and means of removal.

Complications of embolizations (Table 15-1) may occur immediately following embolization or months later. They include arrhythmias, perforation, clotting, and infection (sepsis, endocarditis). Bacterial contamination of foreign bodies has been reported in up to 50% within 48 hours; however, infectious complications resulting from bacteremia are much more rare.⁹ Fatal complications such as injury of the large vessels (tear or rupture of large veins), perforation of the aorta or heart with resulting hemopericardium, tear or damage of the heart valves, embolization into vital structures such as the brain, heart, or major vessels, myocardial infarction, or death
occur rarely.¹⁰,¹¹ However, in some studies death rates up to 24% and 60% have been reported.¹²,¹³

Most foreign bodies need removal (Table 15-2). In only a few cases, the particularly low risk derived from foreign body residence in the vasculature does not justify the risk of attempting retrieval.¹¹

Foreign bodies lost in the peripheral circulation, for instance, can be left alone unless they have a propensity to develop infection, thrombosis, or embolize. If despite the use of available imaging modalities, embolized foreign bodies cannot be localized, the search must be abandoned. This is usually the case with faintly radiopaque foreign bodies lost in the circulation. In these instances, the decision as to long-term anticoagulation will depend on the estimated risk of thromboembolism. Antibiotic therapy is not recommended because it is ineffective. Persistent pain represents an indication for removal of low-risk foreign bodies.

Catheter fragments, devices, guidewires, valve fragments, etc., located in the heart require early removal to avert the high risk of thrombus formation, perforation, arrhythmias, endocarditis, distal ischemia, etc. Similarly, lost intracoronary stents must be retrieved if at all possible. Foreign bodies localized in the large vessels always need to be extracted, as migration of such foreign bodies or occlusion of the large vessels is a possibility harboring disastrous consequences. Foreign bodies, being the source for pulmonary or arterial emboli, also require retrieval.

Percutaneous retrieval obviates the need for surgery and is safer and simpler to perform.¹⁴ Complications of percutaneous retrieval can be injury to the vessel wall (tears, ruptures, and rarely perforation) and perforation and tearing of heart valves and chambers leading to hemopericardium. Clot and air embolism rarely do occur. Emergency surgery may become necessary in selected cases such as failed retrieval of a lost stent in the left main stem, lost septal closure devices, Greenfield filters, or bullet wounds.

The most common source of foreign body embolization is an iatrogenic complication (Table 15-3). Noniatrogenic foreign bodies represent a minority of cases resulting from missile injuries (bullets, splinters) and accidental or purposeful needle sticks. Initially, foreign bodies mainly involved the right side of the heart as a result of severed catheter fragments inserted intravenously. Subsequently, with the advent of angiography and catheter-based therapies, arterial embolizations have also become a significant hazard.⁷

Indwelling catheters such as Hickman catheters are used frequently for infusing long-term antibiotics, anticoagulation, chemotherapy, or nutrition, especially to cancer-afflicted individuals. Their use in the intensive care setting along with monitoring catheters is common. Hence these catheters represent the commonest source of foreign body embolisms. Other commonly retrieved items from the vascular system include wires, catheter fragments, malpositioned or migrated stents, coils, and caval filters.¹⁵,¹⁶,¹⁷,¹⁸,¹⁹,²⁰,²¹,²²,²³ Fragments of these devices migrate unpredictably, and interventionalists are regularly called upon to tackle these problems. The migratory fragments generally lodge distally at bifurcations, or they wedge in narrow vessels. A host of factors determine their path and localization. Route of entry, position of the patient at the time of the detachment, the length, shape, material, and stiffness of the object, and the flow patterns within the vessel and its course play a role, as well as presence and absence of valves and orifice size in relation to the size of the object. Venous foreign bodies commonly lodge
in the superior vena cava, right ventricle, or pulmonary artery. Long catheter fragments introduced into the subclavian or jugular veins frequently get stuck in the right ventricle while one end of the catheter is still retained in the vein itself. In contrast, short catheter fragments tend to migrate into the periphery of a pulmonary artery. Arterial foreign bodies may cause spasms, thrombotic vessel occlusions, or infarctions. Within the coronary artery circulation, foreign bodies generally migrate downstream. However, during attempts to retrieve guidewires, balloon catheter tips, or improperly deployed stents, the foreign body might be displaced retrogradely and migrate anywhere into the peripheral circulation. In the presence of an intracardiac shunt, a venous foreign body may become arterial and vice versa.²⁴ Such a situation should be kept in mind, as this would influence the method of retrieval and may even include repair of the anomaly in one setting.

With expanding indications of pacing and use of newer devices such as implantable cardioverter defibrillators (ICD), biventricular pacemakers, and percutaneous prosthetic valves, device-related problems (infection, dislocation, fracture, etc.) are of increasing importance to the interventionist and call for special extraction devices and techniques.²⁵

Preferable to treatment for any problem are preventive measures. As has been discussed the majority of foreign body embolizations are iatrogenic and are potentially avoidable by simple attention to safety of techniques, proper selection of material, and standardization of procedures.

Most mishaps are due to inexperience, inattentiveness, improper handling, and inadequate diagnostics during positioning or faulty material.²⁶ An anxious patient further complicates things. This can be easily avoided by explaining the procedure to the patient, allaying his fears, and, in case the patient is still irritable, employing adequate sedation. It is needless to add that the physician must be skilled and experienced. In case of a trainee, close supervision is mandatory.

Once a foreign body is embolized, the next step is to localize and decide on retrieval methods, if any. The subsequent sections delve into general measures of detection, instrumentation, and retrieval methods. The last part of the chapter deals with specific instances encountered, and any special investigation, instrumentation, and technique used is highlighted.

Precise localization of the foreign body is of paramount importance, as this guides subsequent strategies such as decision for retrieval, mode of retrieval, and choice of devices to be used. Most of the materials used for manufacturing catheters, intravascular stents, and other devices are radiopaque and are thus detectable by conventional fluoroscopy provided sufficient spatial and contrast resolution. Retrievals are always carried out under fluoroscopic guidance. Biplane fluoroscopy is preferable over monoplane because it can obtain two simultaneous orthogonal projections, allowing better spatial orientation. It also facilitates proper topographic localization of the foreign body without having to move the camera as with monoplane equipment. Monoplane equipment is more time consuming to use, but also efficacious, and the absence of biplane equipment will not significantly hamper foreign body retrieval. Contrast-medium angiography can supplement fluoroscopy by delineation of neighboring vessels or heart chambers, and detect hitherto missed information such as formation of a fistula, cardiac tamponade, or a shunt by a protruding or eroding missile embolus. It can be used as a road-map guide during catheter removal of the foreign body.

The new-generation stents with thinner struts are less radiopaque and are difficult to localize with conventional fluoroscopy. This problem can be further compounded in obese patients. In case of incorrect placement or embolization of such stents, intravascular ultrasound (IVUS) is helpful, but a rough idea of the site of foreign body loss is necessary. IVUS has also been used for localization of embolized prosthetic valve fragments.²⁷

Transthoracic and transesophageal echocardiography can provide invaluable information before and during catheter removal of foreign bodies. It allows for localization of weakly radiopaque foreign bodies entrapped in cardiac chambers as well as in neighboring structures (e.g., large veins, pulmonary artery, and aorta). Furthermore, it identifies thrombus superimposed on foreign bodies, which may be of importance during removal of pacemaker electrodes or catheter fragments. Its utility is also immeasurable in detection of cardiac tamponade secondary to myocardial or vessel perforation due to a dislodged foreign body. Echocardiography adds more information than conventional fluoroscopy, as once a foreign body is detected within the cardiac silhouette, echocardiography can pinpoint the exact location of the foreign body right ventricular outflow tract embedded in the myocardium, proximity to the coronary arteries, and so forth. This then aids the interventionist in further decision making, such as planning a coronary angiography prior to attempting retrieval, and also selecting the mode (surgical vs. medical) of retrieval. One can also do the retrieval under echocardiographic guidance, thereby attenuating blind operative trauma and procedure time. While using echocardiography, the operator should be aware that pericardial calcifications, fibrosis, and so forth can also cause reverberations mimicking foreign bodies. In this scenario the determination of the probable site of localization by conventional radiography may help the cause.

Magnetic resonance imaging (MRI), computed tomography (CT), and 3D echocardiography have added to the investigational pool for detection of difficult-to-see lost devices. Like echocardiography, CT scan and MRI have a specific role in precisely localizing the foreign body (e.g., embedded end of a guidewire missed by conventional radiography). Use of contrast medium adds further information as regards patency of the distal vessel. These highly advanced techniques have limitations such as availability in small centers, practicality of use in emergency situations, and slow acquisition rates in moving targets. Despite all the currently available imaging modalities, some foreign bodies are too small and radiolucent to be detected in the peripheral circulation. Most of these can be safely left alone in the absence of any complication.¹¹

The majority of the retrievals are performed via the femoral route with occasional use of upper-extremity venous access in cases of thrombosis of the inferior vena cava or other central veins. In venous accesses, a double-wire technique²² can be used. In this, two guidewires are placed in the same vein. Over one of the wires a vascular sheath is inserted, and the other lies parallel, acting as a safety wire. This aids in maintaining access for completion of retrieval or if angiography is required, even when one vascular sheath is pulled out with the foreign body. Alternatively, bilateral femoral routes can be used. This is especially useful for problems of knotting of catheters and also the coaxial snare technique (see later discussion).

Since the first description of percutaneous foreign body retrieval there has been considerable progress in techniques and instrumentation. Earlier devices included use of guidewires, pigtail catheters, etc. The earliest and only available retrieval device during the time of description by Dotter et al.¹⁵ was the Curry snare.²⁸ Newer devices used include the wire loop snare, retrieval basket, grasping forceps, tip-deflecting wire, pincher devices, oversize sheaths or catheters, and balloon catheters.¹⁵,¹⁷

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