Scenario
Causes
Bail-out techniques
Trapped equipment
Wires
Prolapsed or knuckled wire is trapped in a calcified or tortuous segment
Wire used to protect a side branch is trapped behind a newly deployed stent
Advance microcatheter or over-the-wire balloon to provide controlled, local traction at the site of entrapment.
Advance the microcathter beyond the highest point of resistance, and the wire can then be removed.
Knotted wires
During aggressive wire ‘knuckling’ or excessive torquing, a knot can be formed
Advance a microcatheter to the point where the wire is knotted and gently pull on the wire to untangle it
Balloons, stents and microcatheters
Stent or microcatheter is aggressively advanced or drilled into a calcified and tortuous vessel
Balloon is ruptured in calcified, fibrotic lesion, becoming entrapped
Device snags on the struts of a newly placed stent
Cut off device hub and advance a guide or telescoping ‘mother-in-child’ guide to the lesion to provide local coaxial countertraction while attempting to withdraw the device
Advance a gooseneck snare over the trapped device shaft to provide traction on the device close to the site of entrapment
Advance a parallel wire and perform angioplasty of the culprit region in the lesion or subintimal space
Rota-burr
Small Rota burr is advanced too quickly past a lesion and cannot be withdrawn
Rota burr is embedded into a calcified lesion or within a previously placed stent
Apply gentle negative pressure while using Dynaglide
Use ‘mother-in-child’ guide or gooseneck snare as above.
Advance a parallel wire and perform angioplasty of the culprit region
Pull on the RotaWire while pulling on the burr
Retrograde scenarios
Wires
Wire trapped in small tortuous collateral
Use a microcatheter to relieve the resistance on the wire, as above
Balloons and microcatheters
Collateral is small and tortuous, has a sharply angulated takeoff, or is jailed by a stent
Remove the externalized wire from the microcatheter to allow it to become more pliable and conform to the tortuous vessel, then remove the microcatheter
Use ‘mother-in-child’ guide or gooseneck snare as above.
Entanglement of antegrade and retrograde gear
Tips of the antegrade and retrograde microcatheters become coupled
Pull both catheters from their proximal extremities
Cut off antegrade device hub and pull back on the retrograde equipment, pulling out all the gear through the collateral and out the retrograde guide
Embolized equipment
Wires, stents, and microcatheter tips
Entrapped portion of device fractures during attempt to withdraw device
Aggressive or careless wire advancement causes the wire tip to prolapse and fracture
Calcified/tortuous lesion causes the delivery balloon to separate from the stent
Micro snare retrieval
Entangle the fragment with 2 or 3 wires and remove
Advance a small balloon or protection device/basket distal to the fragment and drag back
Biopsy forceps can be used for devices in proximal coronaries
Stent the fragment into the vessel wall
Risk Factors
Device entrapment and embolization is most frequently associated with interventions on tortuous and severely calcified vessels [1] and can occur in the left and right coronary arteries equally [3]. The use of collaterals in CTO interventions can predispose to device entrapment. Tortuous collateral channels and septal branches with sharply angulated takeoffs have been associated with retrograde wire [8], balloon, and stent entrapment [7].
During antegrade interventions, it is imperative that the target vessel is properly prepared and the operator avoids forcing stents and other devices to cross lesions. Now that the vast majority of stents are pre-crimped, stent dislodgment is almost always due to aggressive advancement of stents into improperly prepared lesions or distal to previously deployed stents. It is also advised to prep the stent delivery balloon only when the stent is in place; otherwise, negative suction on the balloon can weaken the stent crimping, and increase the chance of stent dislodgment. The use of debulking devices to modify plaque characteristics and create channels through ‘non-crossable’ lesions helps reduce this risk. Inflation of balloons to high enough pressures to cause rupture may lead to the balloon becoming embedded into the vessel and entrapped [9], so there should be a low threshold to utilize atherectomy if a lesion appears non-dilatable.
Advancing equipment through recently placed stents also presents a situation with increased risk for device entrapment. The exposed stent struts can shear off parts of the devices crossing through the cells or along the stent edge. Pulling directly on the device without disentangling it from the stent can cause stent deformation, leading to entrapment. This situation has been described by operators who entagled an IVUS catheter within the struts of a newly placed stent [10] or were performing rotational atherectomy with a stent [11].
The risk for device breakage or stripping stents off of delivery balloons can be reduced by making sure coaxial traction is directed as close as possible to the site of resistance. The non-coaxial force applied to stent delivery balloons due to vessel tortuosity or poor guide positioning has been described as a significant risk associated with stent embolization [1]. Additionally, pulling forcefully on trapped wires and devices can cause trauma to the proximal vessel, or to the weaker weld points on the device, while very little of this force is transmitted to the site of resistance.
Entrapped Equipment
Wires
Although it happens less commonly with newer flexible wires, with more durable weld points, wire entrapment has been reported with prolapsing and extreme torquing of the end of the wire within tortuous distal vessels, along sharply angulated branches, and within calcified, fibrotic lesions. More commonly, wires can become entangled within fresh stents struts, or inadvertently jailed behind stents deployed to high pressure [4].
Continuously increasing traction without any movement of the trapped segment will lead to wire fracture and embolization, or stripping of the polymer coat, so an attempt should be made to apply controlled coaxial traction as close as possible to the entrapped segment using a guide or microcathter while withdrawing the wire. It may be possible to advance a microcatheter beyond the trapped region, or if the wire has been stented, underneath the stent, at which point the wire can be withdrawn through the microcatheter [12]. A braided catheter such as a Tornus or Corsair (Asahi Intecc, Aichi, Japan) may be required to push through the calcified lesion.
During aggressive wire knuckling, while creating or tracking a subintimal channel, concomitant torquing of the wire can lead to the wire being tied into a knot. If as a result the wire cannot be withdrawn, then a microcatheter should be advanced to the knot to help disentangle the wire. Often the wire and microcatheter can then be withdrawn simultaneously. Suggestions for managing embolized wire fragments is described at the end of the chapter.
Bail-Out Technique for Trapped Wires
Use a microcatheter to disentangle and free entrapped wires to avoid fracturing wires while pulling back on them.
Microcatheters, Balloons and Stents
In tortuous, highly angulated vessels, or in severely calcified lesions, microcatheters and stents can become entrapped, especially if the operator progressively advances the catheter by torquing the device, thoroughly embedding it into a lesion. Equipment can also become entangled by advancing it through the cells of a freshly deployed stent into a sharply angulated branch [13] or snagging the balloon on a stent edge [14]. Balloons become entrapped when they are ruptured within a lesion or when the irregular balloon fragments prevent withdrawal of the ruptured balloon through a lesion [9].
If the lesion can be modified, the device can sometimes be extricated. If a large enough guide was used, a second wire can be advanced across the lesion and balloon angioplasty of the lesion can be performed. If the lesion cannot be crossed with a wire, it may be reasonable to track the second wire subintimally around the lesion and perform a high-pressure inflation, attempting to modify the calcified plaque by crushing it from the extraluminal space. If the first guide will not accommodate another wire and balloon, a second guide catheter may be required from a second access site to intubate the coronary artery alongside the first guide (ping pong technique).
Another approach is to cut off the hub of the device to allow advancement of a telescoping ‘mother-in-child’ catheter through the guiding catheter, over the shaft of the trapped device. This second guide catheter can be deep seated and provide coaxial countertraction at the site of entrapment [9].
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