rotational atherectomy ( ra ) is an irreplaceable modality for heavily calcified lesions in current percutaneous coronary intervention ( pci). since incomplete stent expansion is a well - known predisposing factor for further instent restenosis and thrombosis , lesion preparation using ra prior to stent deployment in balloon heavily calcified undilatable lesion is mandatory .
however , some complications may be encountered during ra procedure , including slow or no reflow , coronary spasm , distal embolization , coronary dissection , coronary perforation , fracture of the guide wire ( gw ) , or the drive shaft and entrapment of burr . among these complications ,
it occurs more frequently in off - label use and usually needs surgical removal . here
we report a case series of burr entrapment and discuss the mechanism and management of this complication .
case 1 was a 60-year - old lady with lupus nephritis complicated with end stage renal disease under regular hemodialysis for decades .
rotablation for the heavily calcified left anterior decending artery ( lad ) ( figure 1a ) was performed by 1.5 mm rotablator burr initially and followed by another 1.75 mm one . during the pecking motion of the 1.75 mm burr at 160,000 r / min ,
it was suddenly stuck at the distal lad and could not be activated even after intracoronary nitroglycerin injection ( figure 1b ) .
a hydrophilic fielder fc wire ( asahi intech , japan ) and a stiff conquest wire ( asahi intech , japan ) were tried to pass the entrapped burr for dilation of the segment that entrapped it , but both failed .
the burr was re - activated after increased the speed up to 180,000 r / min and could be advanced distally followed by successful retrieval .
case 2 was a 65-year - old gentleman with type 2 diabetes and dyslipidemia , who was admitted for pci because of unstable angina .
heavily calcified from proximal to distal lad was revealed by both angiography and intravascular ultrasound .
rotablation using a 1.5 mm burr was performed at a speed of 180,000 r / min .
the burr was entrapped at the distal lad during a long run of more than 10 s ( figure 2 ) .
the stuck burr was retrieved by pulling vigorously on the guiding catheter ( gc ) , gw and rotablator burr simultaneously . however , it resulted in a spiral dissection and acute closure at the distal lad , which was successfully rescued by re - wiring and stenting .
case 3 was a 69-year - old woman who was admitted due to stable angina .
ra was performed using a 1.5 mm burr , which was entrapped after passing the angulated segment during the first run ( figure 3 ) . despite all efforts
, the burr could not be retrieved successfully and the patient was sent for emergent surgery to retrieve the burr .
case 4 was a 74-year - old male with left main ( lm ) bifurcation disease and received bypass surgery years ago .
pci for the lm bifurcation and calcified lad lesions was performed because all the bypass grafts were occluded .
a conquest wire was passed distally followed by 2.5 mm balloon inflation at the stenotic lesion to retrieve the entrapped burr successfully ( figure 4 ) .
after stenting for the lad , the lm bifurcation was successfully treated by simultaneous kissing stenting .
heavily calcified lad and left circumflex artery ( lcx ) were found and a 1.25 mm burr was employed first for the lcx lesion . during the pecking motion of rotablation , the burr was suddenly trapped at middle lcx and could not be retrieved ( figure 5 ) .
the entrapped burr was removed by manual traction of the burr and guide wire , which resulted in injury and acute closure at the ostium of lcx .
intra - aortic balloon pump was inserted for hemodynamic support and antegrade flow of lcx was restored by successful re - wiring and stenting .
the burr is olive - shaped and has diamond coating at its distal surface for antegrade ablation , but the proximal part was smooth without diamonds , which prohibits backward ablation .
if a burr was advanced beyond a tight calcified lesion or embedded in a long , angulated and heavily calcified lesion , it can be entrapped .
first , a small burr can be advanced beyond a heavily calcified plaque before sufficient ablation , especially when the burr is pushed firmly at high rotational speed . during high speed rotation ,
meanwhile , the coefficient of friction during 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 . in this situation
this phenomenon was named  kokesi  after the japanese doll by kaneda et al .
second , the burr can be entrapped within a severely calcified long lesion , especially angulated and concomitant coronary spasm .
when a large burr was pushing vigorously against such lesion without sufficient pecking motion , the rotational speed may decrease significantly and this type of entrapment may occur .
an emergent open surgery would be the most reliable and always the last option for removing the entrapped burr , just as the case 3 we reported .
however , surgical removal is invasive , time consuming and usually not immediately available , especially for hemodynamic unstable cases . before sending the patient to surgery , several non - surgical techniques
, to relief spasm and facilitate antegrade coronary flow , intracoronary nitroglycerin and/or verapamil injection are also suggested .
, , the simplest method to retrieve the entrapped burr is pulling back the rotablator system manually . in some cases , as the case 2 and 5 of our series , the stuck burr can be withdrawal successfully by manual traction with on - dynaglide or off - dynaglide rotation but the vessel may perforate and proximal segment may be injured . extreme force on the burr and burr shaft may also result in shaft fracture . disengaged the gc from vessel ositum and sending another gw deep into aorta may prevent vessel injury by avoid deep seating of gc during traction . in some cases ,
set the rotablation speed up to 200,000 r / min and try to advance the burr into the distal lumen may successfully withdrawal the burr while spinning , just as our case 1 .
second , if simple manual traction failed , passing a second gw beyond the entrapped burr followed by balloon dilatation for the calcified lesion proximal to it may create a crack between the burr and vessel wall to retrieve it .
, , , the lesion surrounding the entrapped burr is always heavily calcified and usually need a hydrophilic - coated wire to pass it and sometimes stiffer wire such as conquest wire may be needed to pass the adjacent hard plaque , , as the case 4 of our series .
however , the profile of the rotablation drive shaft sheath is 4.3 fr , which may prohibit introducing of a balloon catheter ( mostly 3 fr in diameter ) into the gc if it is a 6 or 7 fr one . in this situation , introducing another gc via another vascular access may be needed for the second gw and balloon .
, alternatively , the gc may be exchanged to a 8 fr one after cutting off the burr and sheath near the advancer .
, , sakura et al . demonstrated a novel idea to remove the drive shaft sheath after cut off the system near the advancer .
after retracting the sheath and leaving the transected uncoupled burr , a second gw and balloon catheter can easily pass through the gc even it is a 6 fr one .
third , a snare was reported to remove an entrapped burr successfully by parsan et al .
the rotablation system was cut at the hub as described above , which allowed direct access of the snare to the burr shaft .
after encircled the burr shaft by the snare and the noose tightened immediately proximal to the entrapped burr , the burr was successful withdrawal by simultaneously retracting on the snare and the gc . applying the traction force locally to the entrapped burr is a more controlled manner and may reduce the risk of proximal vascular trauma .
fourth , using a child catheter was also reported to retrieve the stuck burr either by over - the - wire 5fr 120-cm straight gc ( heartrail st01 , terumo , japan ) or monorail 5 fr guideliner ( vascular solutions , minnesota , usa ) gc .
after cut off the drive shaft and sheath near the advancer , the child catheter can be inserted through the remaining rotablation system to the entrapped burr . by simultaneous traction on the burr shaft and counter - traction on the child catheter ,
the catheter tip can act as a wedge between the burr and the surrounding plaque , which may exert a larger and more direct pulling force to retrieve the burr .
furthermore , the child catheter may protect the proximal vessel on coronary tree and facilitate following interventional procedures after successful removal of the burr by taking advantage of the child - in - mother technique .
the burr entrapment can usually be avoided by gentle pecking motion and short runs of rotablation ( < 15 s ) .
when a smaller burr was employed , more slowly advancement to ablate the plaque of proximal lesion sufficiently was recommended , and too high a burr speed should also be avoided to prevent  kokesi phenomenon  .
it was also suggested that the speed of rotation per minute should not be drop more than 10% during burr advance to avoid a too large amount of debris being produced within a short time , which may not occur if push gently .
if the burr was push aggressively , it may become stalled and embedded in the calcified lesion ; especially when the lesion is long , heavily calcified , low elastic and high angulated .
, continuous high pressure flushing of nitroglycerin and verapamil can also avoid severe vessel spasm and slow / no reflow .
furthermore , using a stiffer wire to straighten the narrowing to lessen resistance was also been proposed . a stiffer gw dose not always produce an unfavorable bias but sometimes makes favorable bias which may help a sufficient ablation of angulated heavily calcified lesion .
since the burr was diamond - coated only at the distal part , some entrapped burrs may be successful retrieved if the proximal part was also coated by its manufacturer .
burr entrapment is a rare but serious complication during ra and often necessitates open surgery to retrieve the trapped burr .
the mechanisms for such complication include kokesi phemonenon or insufficient pecking motion for long , heavily calcified and angulated lesion .
several bailout techniques other than surgery have been proposed to retrieve the stuck burr such as simple manual traction , passing another gw followed by balloon inflation to release the trap , using a snare immediate proximal to the burr for forceful local traction or a child catheter to facilitate the successful retrieval .
a stiffer wire may be used to straighten the lesion to lessen the resistance unless unfavorable wire bias was observed .
interventional cardiologists using rotablator should be familiar with these tips and tricks to avoid and rescue this complication .
 entrapment of the burr within calcified lesion is an uncommon , but serious complication during rotational atherectomy and usually needs surgical retrieval . 
 we report a case series of this complication and also review the possible mechanisms , such as kokesi phenomenon or insufficient pecking motion with decreased rotational speed . 
 we also review the potential techniques ever proposed to rescue this complication percutaneously , including simple manual traction , balloon dilation to release the trap , snaring the burr as distal as possible for forceful local traction and wedging the burr with a child catheter to facilitate retrieval . 
 gentle pecking motion of the burr for sufficient ablation and shortening the run less than 15 s may avoid such complications . 
 interventional cardiologists using the rotablator should be familiar with the tips and tricks to avoid and rescue this complication . 
Introduction
Case series
Mechanisms of burr entrapment
How to retrieve the entrapped burr?
How to prevent burr entrapment?
Conclusions