Continuing Education Activity

Coronary stenoses with circumferential or significant vessel calcification are rigid and frequently not dilatable with use of conventional balloon angioplasty. Often stent dilation and maximal vessel wall apposition are compromised in extensively calcified coronary lesions, stents deployed in heavily calcified vessels without atherectomy tend to thrombose, restenosis, and could cause stent fracture. Significant calcification remains a major limitation of balloon angioplasty as well as successful stent delivery to severely affected vessels. In cases with heavily calcified lesions, high-pressure, non-compliant balloon inflations may still fail to dilate adequately and prepare a heavily calcified vessel for stent delivery. This activity reviews the indications, contraindications, and complications of rotational atherectomy and highlights the role of the interprofessional team in the management of patients with CAD. Atherectomy refers to the removal of the obstructing material, and in our case this is calcium. By removing significant calcification or modifying the calcified atherosclerotic plaque vessel wall compliance in calcified or fibrotic lesions is increased, and the lumen diameter gained from using this device will be much improved as compared to the use of simple balloon angioplasty. Rotational atherectomy is one of several ways to perform atherectomy in a coronary vessel. It is the most commonly used atherectomy device and removes atheromatous plaque by differential cutting, that is removing the inelastic calcified plaque with microscopic (20 to 50 micrometers) diamond chips embedded on the surface of a rapidly rotating (150,000 to 200,000 rpm) olive-shaped burr. Such abrasion generates 2 to 5-micrometer microparticles that propagate through the coronary microcirculation and are removed by the reticuloendothelial system. The burr travels over a specialized 0.009-inch guidewire and is available in diameters ranging from 1.25 to 2.50 mm. In the setting of severe calcification, smaller burr sizes should be used initially, followed by larger burrs in 0.25 to 0.50-mm increments up to 70% of the reference vessel diameter. This activity describes rotational atherectomy, and explains the role of the interprofessional team in managing patients who undergo this procedure.

Objectives:

• Describe the technique of rotational atherectomy.
• Review the indications for rotational atherectomy.
• Summarize the complications of rotational athetectomy.
• Explain the importance of improving care coordination among interprofessional team members to improve outcomes for patients undergoing rotational atherectomy.

Introduction

Calcium deposits within a coronary artery are a harbinger of previous inflammation, healing, and scarring. Significant calcification is synonymous with significant atherosclerotic coronary artery disease (CAD). Coronary calcification can be spread diffusely throughout coronary arteries, during imaging of the vessel significant calcification can encompass the vessel in a 360-degree manner. Coronary stenoses with circumferential or significant vessel calcification are rigid and frequently not dilatable with use of conventional balloon angioplasty. Often stent dilation and maximal vessel wall apposition are compromised in extensively calcified coronary lesions, stents deployed in heavily calcified vessels without atherectomy tend to thrombose, restenosis, and could cause stent fracture. Significant calcification remains a major limitation of balloon angioplasty as well as successful stent delivery to severely affected vessels. In cases with heavily calcified lesions, high-pressure, non-compliant balloon inflations may still fail to dilate adequately and prepare a heavily calcified vessel for stent delivery.[1][2][3][4] 

Atherectomy refers to the removal of the obstructing material, and in our case this is calcium. By removing significant calcification or modifying the calcified atherosclerotic plaque vessel wall compliance in calcified or fibrotic lesions is increased, and the lumen diameter gained from using this device will be much improved as compared to the use of simple balloon angioplasty. Rotational atherectomy is one of several ways to perform atherectomy in a coronary vessel. It is the most commonly used atherectomy device and removes atheromatous plaque by differential cutting, that is removing the inelastic calcified plaque with microscopic (20 to 50 micrometers) diamond chips embedded on the surface of a rapidly rotating (150,000  to 200,000 rpm) olive-shaped burr. Such abrasion generates 2 to 5-micrometer microparticles that propagate through the coronary microcirculation and are removed by the reticuloendothelial system. The burr travels over a specialized 0.009-inch guidewire and is available in diameters ranging from 1.25 to 2.50 mm. In the setting of severe calcification, smaller burr sizes should be used initially, followed by larger burrs in 0.25 to 0.50-mm increments up to 70% of the reference vessel diameter. David Auth first investigated the possibility of using a rotational device to debulk atherosclerotic plaque in the early 1980s. Fourier et al. performed the first case of RA in human coronary arteries in 1988.[5][6][7][8]

Indications

Rotational atherectomy is currently used for ostial, and heavily calcified lesions that cannot be dilated with balloon angioplasty or those where the stenosis and calcification are so severe a stent cannot be delivered to its target. Rotational atherectomy is generally limited to abrasion of superficial calcification with a single burr to improve lesion compliance before the lesion is treated definitively by balloon dilation and stent placement. Rotational atherectomy is used in less than 5% of percutaneous coronary intervention procedures.

Contraindications

Rotational Atherectomy is most effective in calcified, inelastic lesions,  it will not be effective in soft and thrombus containing lesions as present in acute myocardial infarction or saphenous vein graft lesions with heavy thrombotic burden where its use is contraindicated.

Equipment

The rotational atherectomy device consists of a long catheter with an oval-shaped burr that is encrusted with microscopic diamond embedded surface tip. Through the catheter, a lubricious fluid is pumped in to reduce heat production and burr entrapment during the procedure. The proximal end of the burr is smooth and flat at the end.  The back end of the catheter is connected to an advancer that allows the operator to extend and retract the burr within the vessel.  The advancer is connected to an external console where air or nitrogen is pumped into the advancer through a pneumatic hose to the turbine housed within the advancer to spin the drive shaft and the burr. A foot pedal allows the operator to activate the burr and commence spinning of the burr. The desired rotational speed of the burr is adjusted at the external console.

The coronary guidewire the rotablation catheter rides over has a  diameter body of 0.009 inches with a 0.014-inch tip. The burr is advanced over the 0.009-inch portion of the wire, and the larger diameter wire tip restricts its forward motion. While the burr is actively spinning,  a wire clip is placed to the back of the wire to it prevent spinning of the guide wire and possibly causing vessel damage. When performing rotational atherectomy, a lubricant consisting of a lubricious lipid emulsion is used to reduce friction between the burr and guidewire is added to the flush bag. The rotational atherectomy lubricant is composed of olive oil, egg yolk, phospholipids, sodium deoxycholate, L-histidine, disodium EDTA, sodium hydroxide, and water.

Preparation

Patients undergoing rotational atherectomy are treated in a similar pharmacological manner to patients undergoing balloon angioplasty. Heparin or bivalirudin is administered to maintain the activated clotting time greater than 300 seconds. One of the potentially disastrous complications of rotational atherectomy is the development of slow coronary flow or no flow phenomena. This is defined as a decrease or cessation of blood flow in the absence of an apparent occlusive dissection or spasm. Slow flow and coronary no flow phenomena are thought to occur as a result of distal microparticle embolization that occurs during rotational atherectomy. It is usually treated with intracoronary administration of verapamil, diltiazem, nicardipine, adenosine or nitroprusside. These medications have their effect at the microcirculation level. Many catheterization laboratories routinely use a cocktail of nitroglycerin, verapamil, and heparin in the flush solution that has been shown to reduce the incidence of spasm and slow/no flow.

Technique or Treatment

High-speed mechanical rotational atherectomy relies on plaque ablation and pulverization by the abrasive diamond-coated burr. The rotational atherectomy device can ablate inelastic tissue selectively while maintaining the integrity of elastic tissue due to the principle of differential cutting. Differential cutting is ablating one material selectively while saving and preserving the integrity of another. This is based on different substrate composition, resulting in a polished smooth lumen.

Improvements in technique have included the use of verapamil and nitroglycerin within the flush solution, slow burr advancement, to-and-fro pecking motion of the burr, shorter burr runtimes (15 to 20 seconds), lower burr speeds (150,000 rpm to 160,000), and strict avoidance of significant drops in rpm. These improvements and adjunctive therapies have resulted in significant reductions in the incidence of no-reflow and coronary artery spasm.

Complications

As with all atherectomy devices, complications can arise, and this is not exclusive to rotational atherectomy. Based on multicenter registries and numerous observational studies, these complications include death in approximately 1%, myocardial infarction in 1.2 to 1.3%, and emergency CABG in 1.0% to 2.5% of cases. In addition to the clinical complications, the angiographic complications of RA include artery dissection in (10%), abrupt vessel closure (1.8%), a slow-flow phenomenon (1.2% to 7.6%), perforation (1.5%), and severe spasm (1.6%). Another unique but rare complication of RA is dissection caused by wire bias in the angulated lesion, which can be decreased by bending the guidewire or using a small-size initial burr.

Clinical Significance

In regards to rotational atherectomy burr decelerations, Reisman et al. demonstrated that excessive drops in speed and aggressive advancement of the burr were related to significant increases in temperature and potential thermal injury. In the randomized Study to Determine Rotablator and Transluminal Angioplasty Strategy (STRATAS) trial, decelerations greater than 5000 rpm from baseline for a cumulative time greater than 5 seconds were associated with both an increase in CK-MB elevation and restenosis.[9][10][11][12]

There has been a long-standing controversy regarding the use of an aggressive versus a conservative approach for rotational atherectomy. The proponents of the aggressive approach recommended an aggressive burr-to-artery ratio to ablate plaque optimally followed by low balloon inflation pressures to avoid deep tissue injury. The conservative lesion modification approach recommended under-sizing the burr with the goal of altering the compliance of the lesion and facilitating subsequent adjunctive balloon angioplasty (to pressure as needed to obtain a satisfactory angiographic result). In the STRATAS trial, a total of 500 patients were randomized to either:

• An aggressive rotablation strategy where the burr to artery ratio was greater than 0.7 followed by no angioplasty 
• A routine or “conservative” rotational atherectomy where the burr to artery ratio was less than 0.7 followed by routine balloon angioplasty.

There was a trend toward a higher initial incidence of greater CKMB elevation and target lesion revascularization as well as angiographic restenosis at 6 to 9 months post procedure in the aggressive strategy group. The CARAT trial (Coronary Angioplasty and Rotablator Atherectomy Trial) enrolled 222 patients into aggressive and conservative groups similar to the STRATAS trial. This study suggested that a routine lesion modification strategy employing small burrs achieves similar immediate lumen enlargement and late target vessel revascularization (TVR) compared with a more aggressive debulking strategy, but with fewer angiographic complications. Based on these 2 trials, most operators in practice today generally apply a conservative approach and utilize a burr-to-artery ratio of equal to or less than 0.6.

Coronary artery stenting has been associated with lower restenosis rates compared to balloon angioplasty, but stenting of calcified lesions has not been extensively adopted because of concerns about the inability to expand the stent fully due to lesion calcification and rigidity. Because rotational atherectomy changes lesion compliance, better stent expansion is obtained when stents are implanted in calcified lesions following rotational atherectomy. In the Effects of Debulking on Restenosis (EDRES) trial, 150 patients were randomized to stenting alone versus rotational atherectomy with stenting. The results of this study were notable for a reduced binary angiographic restenosis rate at 6 months post-procedure in the rotational atherectomy with stenting group. Also, in the Stenting Post Rotational Atherectomy Trial (SPORT) study, 750 patients were randomized to receive either balloon dilatation or rotational ablation before stent implantation. The mean burr-to-artery ratio was 0.7 plus or minus 0.1 in the rotational atherectomy group. While procedural and clinical success were higher in the rota stenting group, there were no differences in the rates of in-hospital major adverse cardiac events.

Patients with chronic coronary total occlusions have an unacceptable high restenosis rate after revascularization (50% to 70%) after balloon angioplasty alone, and 20% to 30% after stenting. Plaque debulking prior to stenting may render additional benefits by removing the increased plaque burden seen in this type of lesion and also allow for the optimal stent deployment. In general, once the chronic total occlusion has been crossed with the stiff guidewires (then exchanged for the rotational atherectomy wire), the procedural success rates have been close to 100% in all of the recent series with restenosis rates under 30%, which compares favorably to historical controls.

The percutaneous coronary intervention of aorto-ostial lesions and ostial lesions, in general, remain a difficult and challenging task with elevated rates of procedural complications. Due to the ability to pulverize atheroma, professionals believe that rotational atherectomy may result in improved procedural and perhaps even long-term outcomes. There have been several studies assessing these lesions treated with rotational atherectomy. These studies have shown rotational atherectomy (compared to balloon angioplasty) of ostial lesions improves procedural and clinical success and decreases the need for side-branch intervention, while the restenosis rates are favorable in rotational atherectomy and stenting versus stenting alone in these ostial lesions.

Enhancing Healthcare Team Outcomes

There have been numerous nonrandomized reports evaluating the safety and efficacy of rotational atherectomy for the treatment of in-stent restenosis. Most studies performed reported high procedural success rates and low risk of major complications. One of these studies, the ROSTER trial (Rotational Atherectomy versus Balloon Angioplasty for Diffuse In-Stent Restenosis) demonstrated a favorable effect of rotational atherectomy on restenosis, while the multicenter European Angioplasty versus Rotational Atherectomy for Treatment of Diffuse In-Stent Restenosis Trial (ARTIST) did not show a similar beneficial effect.

Rotational atherectomy has also been proposed as a means of treating undilatable lesions that are composed of fibrocalcific plaque. By partially ablating the fibrocalcific plaque, rotational atherectomy can increase lesion compliance and render it more amenable to subsequent adjunct balloon angioplasty and or stent delivery and deployment. Reports of rotational atherectomy being utilized for this type of lesion have reported with a success rate of more than 90%. It has also been suggested that if lesions do not crack despite the use of high-pressure noncompliant balloon dilatations, subsequent rotational atherectomy using small burr sizes can still be performed safely so long as there are no visible dissections within the artery. Rotational atherectomy has also been reported to be successful in a step-wise approach with slow progression of burr size from 1.5 to 1.75 to 2.0 in pulverizing previously deployed multiple layers of stents that have been under-deployed and continue to suffer from significant in-stent stenosis. These anecdotal case reports have noted greater than 90% procedural success with minimal incidence of slow or no-reflow phenomena.

The main indication for the use of rotational atherectomy at present is to alter lesion compliance in calcified and or undilatable lesions to facilitate stent delivery and expansion. When rotational atherectomy is performed, it should be followed by stenting in most lesions where possible. Overall rotational atherectomy has a firm place in our interventional armamentarium in treating heavily calcified and complex lesions by rendering the procedure simple and effective, but without any effect on restenosis or long-term clinical events. [13][14][15](Level II)

Once the patient is treated, the primary role of the nurse, nurse practitioner, and primary care provider is to encourage the patient to reduce the risk factors for coronary artery disease. This means eating a healthy diet, discontinuing smoking, weight loss, regular exercise, and remaining compliant with medical therapy.