Burr Entrapment – Case 2
- 87-year-old male who presented with chest pain (CCS Class II).
Past Medical History
- HTN, HLD, DM, CAD s/p PCI, Former Tobacco Use, Atrial Fibrillation
- LVEF 68%
- Stress MPI: Severe anterior ischemia.
- Home Medications: Aspirin, Clopidogrel, Warfarin, Simvastatin, Metoprolol Tartrate, Diltiazem, Spironolactone, Allopurinol, Colchicine, Finasteride
- Adjunct Pharmacotherapy: Clopidogrel, Bivalirudin
- 90-95% calcified lesion in the ramus intermedius (RI).
- Underwent intervention of the RI.
- Procedure was complicated by entrapment of a 1.5mm rota burr in a long calcified segment of the RI.
- Mother and child catheter technique was used to successfully retrieve the entrapped burr.
- Procedure was continued and successful intervention of RI was performed.
- Troponin-I peaked at 0.1 ng/mL and CK-MB peaked at 2.8 ng/mL.
- Patient was discharged home next day without further sequelae.
- What is the likely explanation or reason why the complication occurred?
- Two mechanisms for burr entrapment include:
- ‘Kokesi’ phenomenon: When performing rotablation at high RPM, frictional heat is generated and it may enlarge the space between plaque. In addition, the coefficient of friction when the burr is in motion is less than that at rest, which may facilitate the burr to pass the calcified lesion easily without debulking a significant amount of calcified tissue. Once the burr traverses the lesion, and the plaque cools the between the plaque is again reduced, and the ledge of calcium proximal to the burr prevents the withdrawal of the burr, which is known as ‘Kokesi’ phenomenon, a name given after a Japanese doll.
- Burr can become entrapped within a severely calcified ,long and/or angulated lesion when the burr is advanced aggressively. When a large burr is pushed forcefully against this kind of lesion without an appropriate pecking motion, significant decelerations occur and this produces more debris which increases the risk for slow flow/no-reflow and burr entrapment.
- How could the complication have been prevented?
- The burr is oval shaped and coated with diamonds at its distal end, allowing for antegrade ablation. However, the proximal end is smooth and not coated with diamonds, prohibiting retrograde ablation. If a burr is advanced beyond a tight calcified lesion or embedded in a long, angulated and heavily calcified lesion, it can be entrapped. Burr entrapment can often be avoided using the following techniques/strategies:
- Use a gentle pecking motion with shorter runs of ablation (<20s).
- Do not exert excessive forward force during burr advancement. If the burr is advanced aggressively, it causes decelerations and can become embedded in the calcified lesion.
- The risk for burr entrapment is greater when the lesion is long and heavily calcified, and the vessel is highly angulated.
- When advancing the burr, avoid decelerations >5000 RPM because this results in more debris production and increases risk for slow flow/no-reflow and burr entrapment.
- When using a smaller burr, avoid using a higher speed of rotation (>180k RPM) to prevent ‘Kokesi’ phenomenon.; optimal speed is around 150k RPM.
- If the vessel or lesion is highly tortuous/angulated, a stiffer wire can be used to straighten the vessel or lesion to lessen the resistance and reduce wire bias.
- Avoid performing rotational or orbital atherectomy in vessels which are highly tortuous, especially if severe wire bias is present. Consider using Intravascular Lithotripsy (IVL) (off label use in the USA) for plaque modification and treatment of calcified CAD.
- Is there an alternate strategy that could have been used to manage the complication?
- Several bailout techniques can be used to retrieve a trapped burr, but prior to proceeding forward.
- Assure patient is adequately anticoagulated (ACT >300) before attempting percutaneous retrieval.
- Administer intracoronary vasodilators to facilitate antegrade coronary flow and relieve possible spasm.
- Potential strategies for retrieval of an entrapped burr include the following:
- 1st: Manual traction of the rotablator system by pulling the burr, guidewire and/or guide catheter as a unit. This can be performed on or off Dynaglide. The vessel is at risk for perforation, dissection, and abrupt vessel closure (AVC). In addition, the burr shaft can fracture. If you are pulling the burr and guidewire as unit (and not the guide catheter), remember to disengage the guide catheter to prevent injury to the coronary artery from it deep seating during traction.
- 2nd: Pass a second wire (hydrophilic-coated guidewire) beyond the trapped burr, followed by balloon dilatation around the burr. This may alter the architecture of the calcified lesion and possibly free the trapped burr. However, a 4.3 Fr rotablation drive shaft sheath may prohibit introduction of a balloon catheter into the guide catheter (consider this possibility if using a 6 or 7 Fr guide catheter). To overcome this, use a two-catheter strategy (Ping-Pong technique) where a second vascular access is obtained and equipment necessary for burr retrival is introduced through. If a single guide catheter strategy is preferred, there are two options. On approach includes cutting the rota system near the advancer, and remove the sheath to expose the driveshaft surrounding the rota-wire. This approach makes room for introduction of a second guidewire and balloon. This approach is useful when using a 6 Fr guide catheter. Alternatively, you can upsize the access sheath and guide catheter to a 8 Fr.
- 3rd: Mother-child catheter technique can be used to wedge the burr and facilitate retrieval. The system is cut near the advancer, and the Teflon sheath is removed exposing the driveshaft which surrounds the rota-wire. A child catheter (monorail 5 Fr Guideliner or 5 Fr Guidezilla) is inserted over the exposed drive shaft and positioned as close as possible to the entrapped burr. With simultaneous traction on the burr shaft and counter-traction on the child catheter, the catheter tip wedges between the burr and the surrounding plaque, exerting a larger and direct pulling force to retrieve the burr.
- 4th: Exclusion with a stent (As was done in this case).
- 5th: Emergent surgical retrieval should always be the last option for removing an entrapped burr, but is often required.
- What are the important learning points?
- Interventional cardiologists who use rotablation, must be familiar with complications associated with its use and their management, particularly burr entrapment which is a rare but serious complication (incidence is ~0.4%, and occurs more frequently when rotablation is used off-label).
- Use a burr which is appropriately sized for the vessel; ideally the burr should be 0.5-0.6x the reference vessel size when performing a plaque modification strategy and 0.8-0.85x the reference vessel size when performing a debulking strategy (STRATA trial). With plaque modification strategy the purpose is to disrupt the calcium so it allows for safe passage of devices and easier expansion of device, balloons, and stents. With debulking, the aim is to break the calcium into particles so it can move through the coronary artery and eventually washout of the coronary microcirculation.
- Consider upfront use of an extension catheter to navigate across a tortuous vessel. With the extension catheter already in position a quick bailout strategy may be feasible should a complication arise while performing rotational atherectomy.
- Prior to retracting the burr using the various techniques above, consider disengaging the guide catheter and holding it fixed with one hand (usually the left) to prevent injury to the coronary artery from it deep seating while pulling the equipment with the opposite hand (usually the right).