Devices in the Lab

Rotational Atherectomy: An Invaluable Tool for Complex Lesions

Michael S. Lee, MD, FACC, FSCAI, Assistant Professor of Medicine, UCLA Medical Center, Los Angeles, California
Michael S. Lee, MD, FACC, FSCAI, Assistant Professor of Medicine, UCLA Medical Center, Los Angeles, California

One of the Achilles’ heels of percutaneous coronary intervention (PCI) is severe, complex calcification. The presence of severe calcification in vessels may prevent the full balloon dilatation of a lesion. Optimal stent expansion and apposition are the key to successful treatment. A stent that cannot be fully expanded because of an undilatable lesion (“stent regret”) can increase the risk of stent thrombosis and restenosis. Plaque modification and debulking of heavily calcified and undilatable lesions with rotational atherectomy (RA) (Boston Scientific Corp., Maple Grove, Minn.) facilitates stent delivery as well as prepares the lesion prior to stenting (Figures 1-4).1

The mechanism of RA is “differential cutting,” whereby noncompliant tissue (i.e., calcified or fibrotic lesions) is selectively ablated and elastic tissue (i.e., non-calcified or non-fibrotic vessels) is not. Atherectomy leads to a “cored out” appearance as atheromatous plaque is pulverized into microparticles, which are then released into the distal coronary circulation. The number of RA cases worldwide has increased over the past 5 years (2005 – 29,960 cases; 2009 – 42,266 cases; data provided by Boston Scientific), possibly reflecting the performance of PCI in more complex lesions since the introduction of drug-eluting stents (DES).

The RA system includes the burr, Rotawire, console, and nitrogen tank. The selected burr size should be approximately 50% of the vessel diameter.2,3 A 6 French (F) guiding catheter can accommodate a 1.25 mm burr. A 7F guiding catheter is the minimum size required for burr sizes ranging from 1.5 mm to 2 mm. An 8F guiding catheter is the minimum size required for the 2.15 mm burr. A 10F guiding catheter is required for a 2.5 mm burr.

The 2 unique guide wires used for directing the burr are the Rota-Floppy and the Rota Extra Support guide wires. The length of the wires is 330 mm, and the body of the wire is 0.009 inches. The maximum tip diameter is 0.014 inch. The Rota-Floppy guide wire has a long, tapered shaft that is designed for greater flexibility and to minimize unfavorable guide wire bias. The Extra Support guide wire has a short, tapered shaft that maximizes straightening of the vessel and provides extra support during advancement of the Rotablator burr into lesions. The floppy wire is a softer, less traumatic wire than the Extra Support wire and is more commonly used. Because the Rotawire is susceptible to kinking and fracture, and is less torqueable than standard guide wires, a more steerable standard workhorse wire can be used to cross the lesion, followed by swapping for a Rotawire with an exchange catheter. The Rotaclip is a torquing device and secondary brake that can be used to prevent the wire from spinning and possibly traumatizing the vessel during ablation and burr exchanges.

The nickel-coated brass burr, embedded with microscopic diamond chips on the front half, is rotated on a Rotawire at 140,000 to 180,000 rpm by an external compressed-nitrogen turbine which is activated by a foot pedal connected to the console (Figure 5). The Rotablator console can be adjusted to control the speed of the burr rotation by regulating the flow of air to the advancer (Figure 6). It also monitors and displays the speed of the burr rotation and procedural time. At our institution, the nurse closely reads out the speed and notifies the operator if there is a deceleration of >5,000 rpm. The STRATAS study identified that CK-MB elevation was associated with a decrease in rpm of >5,000 from baseline for a cumulative time >5 seconds (p = 0.002).2

A pressurized saline drip is continuously infused through the drive shaft to just proximal to the burr. It decreases the friction and heat generated from the burr rotating at high rpms. An optional lubricant, Rotaglide, can be added to the saline bag. Rotaglide may further reduce heat generation and the amount of force required to advance the burr. Some hospitals utilize a cocktail consisting of verapamil (10 mg/L), nitroglycerin (4 mg/L), and heparin (2,000 units/L), which was developed to prevent spasm and in situ thrombosis with rotational atherectomy.4

Prior to ablation, a transvenous pacemaker should be considered in patients, especially if the procedure involves the right coronary artery or left circumflex artery (particularly if it is the dominant vessel), because of the risk of bradycardia and asystole. If not, it should be kept in the room in the event that bradycardia does not respond to atropine. 

RA is contraindicated in saphenous vein grafts (which are at high risk for distal embolization), thrombotic lesions, the presence of a dissection, in cases where the guidewire cannot traverse the lesion, and if the lesion is in the last remaining patent vessel. RA may increase the risk of perforation in severely angulated (≥ 45°) or tortuous lesions due to eccentric passage of the burr.  RA should be used with caution if there is severe left ventricular dysfunction (ejection fraction < 30%). Hemodynamic support with an intra-aortic balloon pump counterpulsation or left ventricular assist device should be strongly considered prior to atherectomy in such cases. However, myocardial damage from distal embolization in patients with marginal left ventricular function may lead to worsening heart failure. Long lesions (≥ 25 mm) may increase the risk of distal embolization.

The heparinized, pressurized flush solution should be infused and the Rotaclip torquer attached to the distal end of the Rotawire. Once the burr is advanced several centimeters proximal to the hemostatic valve, an out-of-body test should be performed to prime the Rotablator and set the desired “platform” speed (typically 150,000 to 170,000 rpms). The advancer knob should be checked for free movement.

Once the burr has been primed, it is advanced forward by the operator under fluoroscopy, with an assistant holding the wire taut to prevent any kinking or buckling of the wire. If there is difficulty advancing the burr from the guiding catheter into the artery, the operator should hold gentle forward pressure on the guiding catheter near the sheath with the left hand for extra support while simultaneously advancing the burr yet holding the hemostatic valve taut with the right hand. Once the burr is proximal to the lesion, several steps can be performed to release any tension to prevent the burr from “jumping forward” and possibly causing vessel dissection. The advancer knob should be released and moved back and forward, the drive shaft should be gently pulled back, and the burr should be briefly activated in the DynaGlide mode (approximately 40,000 rpm). Excessive resistance of the burr may lead to a drop in the speed of greater than 5,000 rpm.

Optimal guiding catheter position is needed to provide adequate support. Once the burr is several centimeters proximal to the lesion, the burr tracks over the wire and is advanced in a smooth pecking motion until the burr passes the lesion. During the ablation, frequent flushes of saline from the manifold should be given to ensure the microparticles flush downstream. “Burr stall” and a drop in the rpm may occur if the burr is pushed too hard and meets resistance. The nurse also notifies the operator at 10-second intervals. The rpm should be maintained within 5,000 rpm of the platform speed. A change in the sound of the Rotablator during ablation should alert the operator of deceleration. Each run should be less than 30 seconds. If the blood pressure decreases, contrast should be injected to assess for vessel dissection, slow flow due to distal embolization, or perforation. Intravenous administration of phenylephrine may be required to rapidly increase the blood pressure. If the wire is inadvertently pulled back, the wire may be advanced in the DynaGlide mode. 

The burr is removed under fluoroscopy to ensure that the Rotawire does not move while the foot pedal is depressed in the DynaGlide mode. Once the burr is removed, another burr can be attached to the Advancer to perform repeat atherectomy. The RotaLink system permits changing of the burrs without replacing the entire drive unit. The RotaLink Plus System comes with a pre-connected burr, but can be exchanged for larger sizes if required. After atherectomy, an over-the-wire balloon or exchange catheter can be used to exchange the Rotawire for a standard guide wire to finish the intervention. Alternatively, the Rotawire can be withdrawn after a standard guide wire is advanced across the lesion.

With RA, complications occur more frequently compared with balloon angioplasty and stenting. Intimal dissection is relatively common. Balloon angioplasty, followed by definitive treatment with stenting, is often successful in tacking down the dissection flap. Traumatic injury to the media and adventitia can lead to coronary artery perforation. Coronary artery perforation is uncommon (1.5%), but can be a catastrophic event and may require emergent, possibly life-saving treatment.5 Perforations are more common in bends and tortuous segments, and with larger-size burrs. Initial management of a coronary artery perforation should include immediate inflation of a balloon to control bleeding and reversal of anticoagulation with protamine if unfractionated heparin has been used. A covered stent may be used if there is persistent extravasation of contrast despite prolonged balloon inflation. Platelets should be administered if patients received glycoprotein IIb/IIIa antagonists or thienopyridines. Patients who develop hemodynamic collapse may require emergent pericardiocentesis to treat cardiac tamponade. Therefore, a pericardiocentesis kit should be readily available in the cardiac catheterization lab. If time permits, an echocardiogram can be performed to assess for cardiac tamponade and echocardiography-guided pericardiocentesis. A cardiac surgeon should be called for emergent, life-saving pericardial window and possible repair of the coronary artery if bleeding cannot be controlled, if the patient has hemodynamic collapse from cardiac tamponade, or if pericardiocentesis is unsuccessful.

Non-ST-elevation myocardial infarction is not uncommon after atherectomy. Slow or no flow from distal embolization can occur from transient increase in blood viscosity due to the formation of microparticles and/or vasospasm in the microvasculature. Intravenous administration of phenylephrine can provide prompt restoration of blood pressure if hypotension occurs. Sustained hypotension may necessitate inotropes like dopamine or intra-aortic balloon counterpulsation, in severe cases. Measures to minimize distal embolization include shorter ablation times (<30 seconds/run), smaller burr-to-vessel ratios (1:2) with gradual upsizing to prevent embolization of large particles, slow burr advancement with a “pecking” motion to prevent a deceleration of >5,000 rpm, repeated flushes with saline boluses via the manifold, and sufficient time between runs to allow for washout of debris. Platelet activation and kinin release is related to rotational speed. Therefore, lower rpm (150,000 rpm) may minimize distal embolization. Intracoronary administration of calcium channel blockers and adenosine, as well as glycoprotein IIb/IIIa receptor antagonists, may be helpful. Non-ST-elevation myocardial infarction can also be caused by coronary artery spasm. Coronary artery spasm can be treated with intracoronary vasodilators like nitroglycerin, verapamil, nitroprusside, or adenosine. Severe cases of coronary spasm that are refractory to vasodilators can lead to abrupt vessel closure which may require balloon inflations.

An uncommon complication is entrapment of an atherectomy burr.6 A 1.25 mm burr was unsuccessfully retrieved from the vessel after atherectomy. It was believed that the small burr passed through the calcified lesion without sufficient debulking of the heavily calcified lesion. Initial pass with a larger burr (1.50 mm) may have debulked more tissue, allowing for easy removal of the burr. This required balloon dilatation of the calcified lesion to create a larger channel to remove the burr from the vessel. Another maneuver to withdraw a burr is to pull the Rotawire back until the tip is at the end of the burr and gently pull out of the vessel. Bradycardia may be prevented by the prophylactic placement of a transvenous pacemaker, particularly during right coronary artery interventions. Ventricular tachycardia requiring treatment may also occur. 

Rotawire fracture is uncommon (2.8%), but can occur, especially when the burr coming out of the guiding catheter is not coaxial with the right coronary artery.7 The right anterior oblique view is helpful to confirm coaxial guiding catheter placement. 

In conclusion, as the safety and efficacy of drug-eluting stents improve, the number of percutaneous revascularizations of complex coronary artery disease will continue to grow. Rotational atherectomy is an invaluable adjunctive therapy to treat heavily calcified, fibrotic, and resistant lesions that require plaque modification and debulking prior to stenting. Full stent expansion and apposition that results from RA decreases the risk of stent thrombosis and restenosis.

This article received a double-blind peer review from members of the Cath Lab Digest editorial board.

Dr. Lee can be contacted at mslee@mednet.ucla.edu

References

  1. Moussa I, Moses J, Columbo A, et al. Coronary stenting after rotational atherectomy in calcified and complex lesions. Circulation 1997;96:128–136.
  2. Whitlow PL, Bass TA, Kipperman RM, et al. Results of the study to determine rotablator and transluminal angioplasty strategy (STRATAS). Am J Cardiol 2001;87:699–705.
  3. Safian RD, Feldman T, Muller DW, et al. Coronary angioplasty and rotablator atherectomy trial (CARAT): Immediate and late results of a prospective multicenter randomized trial. Catheter Cardiovasc Interv 2001;53:213–220.
  4. Cohen BM, Weber VJ, Blum RR, et al. Cocktail attenuation of rotational ablation flow effects (CARAFE) study: Pilot. Cathet Cardiovasc Diagn 1996;3:69–72.
  5. Ellis SG, Popma JJ, Buchbinder M. Relation of clinical presentation, stenosis morphology, and operator technique to the procedural results of rotational atherectomy and rotational atherectomy-faciliated angioplasty. Circulation 1994;89:882–892.
  6. Grise MA, Yeager MJ, Teirstein PS. A case of an entrapped rotational atherectomy burr. Catheter Cardiovasc Interv 2002;57:31-33.
  7. Safian RD, Niazi KA, Strzelecki M, et al. Detailed angiographic analysis of high-speed mechanical rotational atherectomy in human coronary arteries. Circulation 1993;88:961–968.