Unintended loss of material during catheter-based cardiovascular procedures is uncommon but may have serious consequences. Occasionally, a lost or embolized item ends up in a small peripheral vessel, where it can be left in place safely. More often, retrieval of the lost material is desired to reduce risks of thrombosis, infection, and perforation.

The problem of lost foreign bodies in blood vessels is long-standing; early reports of percutaneous vascular foreign body removal first appeared 50 years ago.^1,2 A review of the published literature in 1991 found nearly 200 reported cases with a percutaneous retrieval success rate of 90%.³ A more recent review concluded that percutaneous retrieval of peripheral intravascular foreign bodies has a high success rate and minimal morbidity and is preferable to open vascular surgical removal.⁴ All manner of gear has been liberated into blood vessels (filters, plugs, coils, torn balloon fragments, rotational atherectomy burrs, fractured catheters, percutaneous heart valves), but in the adult catheterization laboratory, losses most often involve retention of fractured coronary guide wire fragments or unexpanded coronary stents that have been stripped free of their delivery balloon catheters. Stent loss and attempts at their retrieval are associated with increased rates of complications, including need for coronary artery bypass grafting surgery, myocardial infarction, and death.⁵ Loss of foreign bodies in the coronary arteries has been reported to occur in slightly less than 1% of cases,⁶ but retention and embolization events are likely to be significantly underreported. As radial artery access gains in popularity, retrieval of lost foreign bodies may prove more difficult, although the techniques described herein have proven useful in this setting.⁷ Optimal management of lost interventional products requires (1) judgment about when to leave retained components in place and when to remove them; (2) knowledge of those techniques proven to be effective and efficient at foreign body removal; and (3) competency with a few specialty devices designed to assist in component removal.

Significant harm can befall a patient with a retained component. Although late infection, perforation, and even material toxicity are concerns, the principal anxiety is thrombosis; occurring in a coronary artery or similar sensitive vessel, thrombosis around a foreign body can be fatal.⁸ However, extraction of foreign bodies from the vascular system carries risk. Thus, before attempting to retrieve a misplaced or embolized component, it is reasonable to ask, “Can I just leave the foreign body where it is?”

Several factors must be considered in the decision process:

1. 
   

   Is the retained component in a location that is highly sensitive to the impact of thrombosis? A sudden thrombotic event in any blood vessel is unwanted but is more easily tolerated in noncritical locations. Fragments left in the left main coronary artery; the proximal portions of the left anterior descending arteries or dominant left circumflex or right coronary arteries; the profunda femoralis; or any cranial artery represent very high risk of harm in the event of thrombosis. Those in arterial or venous structures serving somatic tissue (not organs) are least sensitive to thrombosis.

   
   
2. 
   

   Is the retained component deformed in such a manner that it disturbs blood flow significantly? A study of coronary stent design found that increasing stent thickness from approximately 81 to approximately 161 μm increased thrombus development by approximately 150% in animals and ex vivo flow chambers.⁹ Lost components typically intrude into the vessel lumen to a much greater extent. Venous structures may be more prone to thrombosis related to flow perturbation than arteries even when antiplatelet therapies are used. The more adherent a component is to the vessel wall, the less blood flow is disturbed, and clot risk is reduced. In general, smaller fragments that lay close to the vessel surface are better candidates for conservative management.

   
   
3. 
   

   Can the component be compressed? In view of the above, reducing the profile of an offending component may significantly reduce the risk it poses. This is especially attractive for coronary stents,¹⁰ which are meant to be compressed into the vessel wall, but compressing other materials into vessels (especially benign peripheral arterial locations) may be safer than attempting component retrieval. If conservative management is under consideration, an attempt to reduce the profile of the retained fragment through balloon angioplasty should be considered.

   
   
4. 
   

   Does the retained fragment extend from one vascular area to another? A fractured guide wire may be unspooled over a distance of several feet, resulting in a trail of thin wire that may extend from a coronary artery to the descending aorta. This imbues risk to multiple vascular segments simultaneously and favors fragment retrieval. The thin filaments of wire, when adjacent to coronary stents or other vascular objects, appear to create an environment of high risk for thrombosis.⁸

   
   
5. 
   

   Is the approach to the retained component with a retrieval device complicated? The simpler the approach, the greater the likelihood that the component will be extracted safely. Excessive tortuosity, diffuse vascular disease, calcification, thrombosis, and (especially) small vessel caliber make component retrieval more difficult. Although these characteristics likely contribute to thrombosis risk also, the risk of causing additional harm during attempted retrieval may be prohibitive. Note that retained foreign bodies that are entrapped pose greater risk than those that are simply embolized.¹¹

Snares

Snaring devices remain the most useful and ubiquitous commercial retrieval devices available. Before the widespread availability of commercial vascular snares, loop snares were fashioned by doubling over a long coronary guide wire,¹² feeding both ends of the wire into the distal end of a vascular catheter, and pulling the wire ends simultaneously at the proximal end of the catheter to collapse the loop of wire formed at the distal catheter tip (Fig. 50-1). Creating a kink in the mid-portion of the guide wire before it is inserted can be helpful, since this facilitates formation of a rounder loop. Unfortunately, these crude loops lack maneuverability: the plane of the loop runs parallel to the catheter, limiting utility. Attempting to angle the loop before insertion can be somewhat helpful, but creating a loop that deviates from the axis of the delivery catheter by more than 20° to 30° is difficult.

Commercial loop snares are now widely available in a variety of sizes and shapes, including loops with angles (relative to the delivery catheter) ranging from 0° to 90° and snare diameters ranging from 2 to 35 mm (Fig. 50-2). Snares with loops less than 10 mm in diameter are generally referred to as “micro-snares,” Commercial snares are made of complex alloys, like braided nitinol, that hold their shape much better than steel-based wires. The snare portion may be coated in gold or other radio-opaque material to enhance fluoroscopic visualization. Closure of the snare is affected by retracting a lever or a single wire, which can usually be locked into place with a turnscrew device, freeing hands for other purposes. The catheter portion ranges in length from 65 to 120 cm (micro-snares may be up to 175 cm) and are typically 4 to 6 Fr in diameter.

Variants on the single-loop snare theme include the EN snare (Merit Medical, Jordan, UT), which incorporates 3 interlaced nitinol loops angled 120° from one another that form a tulip-shaped device when opened (Fig. 50-3). Seven different snare configurations and sizes ranging from 2 to 45 mm provide broad applicability; the delivery catheter is 6 Fr. A 4-loop device that forms a clover-shaped snare is appropriately called a CloverSnare 4-Loop Retrieval System (Cook Medical, Bloomington, IN) (Fig. 50-4). Designed chiefly for use in the peripheral arterial system, this 6-Fr system uses a telescoping guide delivery system; the outer sheath is 80 cm, the inner sheath is 85 cm, and the snare catheter length is 90 cm.