Introduction
Calcified coronary lesions present an important challenge to interventional cardiologists. Because of the rigidity and noncompliance of a heavily calcified coronary artery segment, heavy calcification was a risk factor for traditional balloon angioplasty failure and remains associated with major adverse cardiac events after stenting lesions with moderate/heavy calcification in patients with acute coronary syndromes and decreased success for chronic total occlusion percutaneous intervention today. In the setting of severe luminal narrowing or speculated calcification obstructing the vessel lumen, the operator may be unable to pass balloons or stents. Fibrocalcific plaque is often difficult to dilate, reducing acute luminal gain and therefore limiting stent expansion. This in turn increases the risks of restenosis as well as stent thrombosis.
Furthermore, attempts to dilate these lesions with high-pressure balloon inflation increases the risk of extensive dissection and perforation.
It is therefore imperative that contemporary interventionalists are well versed in techniques to modify moderately to heavily calcified segments. These techniques include percutaneous transluminal rotational atherectomy (PTRA), orbital atherectomy (OA), scoring balloon and cutting balloon angioplasty (SBA and CBA), and excimer laser coronary atherectomy (ELCA).
Percutaneous Transluminal Rotational Atherectomy
High-speed rotational atherectomy was introduced in the 1980s by David Auth as a mechanism to ablate atheromatous plaque by slowly advancing a spinning, diamond-coated burr. PTRA was approved for coronary use by the FDA in 1993. The procedure utilizes the principle of “differential cutting” in which the atherectomy device preferentially ablates inelastic tissue composed of fibrotic or calcific components and is safely deflected by more elastic tissue. The technique was intended to improve acute luminal gain with less deep-wall injury compared with balloon angioplasty alone, which in turn should logically reduce the risk of restenosis. In the contemporary stent era, PTRA was further expected to reduce in-stent restenosis due to a reduction in residual plaque burden and improved apposition between the stent and vessel wall.
Procedural Details
The currently available Rotablator system (Boston Scientific, Natick, Massachusetts) consists of a 4.3 Fr, 135-cm drive shaft through which passes a brass burr coated with small diamond crystals on the leading surface ( Figure 12-1A ). The burr is advanced slowly forward into the lesion and alternatively withdrawn using the Rotalink advancer system ( Figure 12-1B ) to allow forward flow with particle disbursement. Run times are limited to 15 to 30 seconds. During advancement, forward pressure applied to the burr is monitored carefully to minimize RPM drops >5,000 from baseline. Large RPM drops are associated with heat production and an increase in particulate size. After each run, the burr is disengaged from the lesion and forward flow is restored for at least 20 to 30 seconds to allow ST segments to normalize and systemic vasodilation to resolve. Runs are repeated until the lesion is fully crossed and ablated.
The entire system is attached to the Rotablator console that is connected to a tank of compressed nitrogen that is delivered to the console at 90 PSI to 110 PSI to spin the Rotablator turbine and burr ( Figures 12-1C and 12-1D ). The gas tank should contain at least 500 PSI of pressure. Delivery of the compressed gas to the burr is regulated by depression of the operator’s foot pedal ( Figure 12-1E ).
The coronary artery is first wired using either the RotaWire Floppy or RotaWire Extra Support guidewire, depending on the characteristics of the vessel and lesion. Both wires consist of a 0.009-inch body and a 0.014-inch tip. The floppy wire is used most commonly, though the extra support wire may be helpful in distal lesions or very heavily calcified lesions. Given the 0.009-inch body and the absence of a lubricious coating, the Rotavirus is difficult to navigate, and a routine coronary wire may be useful to first wire the vessel and exchange for the RotaWire of choice via an over-the-wire balloon or microcatheter.
Prior to insertion of the burr into the back of the guide, the operator should be assured that the rotaflush is seen dripping through the drive shaft. The burr should also be tested and intended RPM set on the console, usually 150,000 RPM to 180,000 RPM ( Figure 12-1D ). With the burr held above the patient’s drape, the turbine is activated and the nurse/technician should turn the power dial until the desired baseline RPM is achieved. The Rotablator system is then advanced over the wire to a position just proximal of the lesion of interest. It is important that two operators work together in this process; one should “pin” the wire as the other advances the system through the guide (as with an over-the-wire balloon or microcatheter device).
Once the burr is in place, the operator then activates the turbine and advances the burr slowly and steadily back and forth across the lesion. It is imperative that the burr is withdrawn completely from the lesion before stepping off of the pedal, as this can cause the burr to become entrapped in the calcified lesion.
Pushing the burr too firmly or allowing stored tension on the wire to lurch the burr suddenly forward can cause the rotating burr to pass through the lesion without adequate ablation. This operator error may rarely cause the burr to become entrapped distal to the intended lesion. Careful attention to procedural details is necessary to avoid complications.
Once the atherectomy is completed, the DynaGlide should be activated, which provides a 60,000 RPM to 90,000 RPM spin of the burr to facilitate extraction of the system over the wire. Simultaneously, the brake must be disengaged and the entire system smoothly retracted over the wire. Care should be taken at this step to not remove the foot from the pedal or inadvertently reengage the brake, as either could result in pulling the wire out of the vessel along with the burr. This step is most safely performed under continuous fluoroscopy to assure wire position in the vessel.
The choice of initial burr size is dependent on the lesion and the size of the coronary vessel. To minimize complications such as coronary dissection and perforation, it is recommended that the operator not exceed a burr/artery diameter ratio >0.7. Operators may start with a 1.5-mm or 1.75-mm burr to create a channel and access the passage across the lesion. In patients undergoing PCI of a particularly long or severe lesion, it is occasionally necessary to start with a 1.25-mm burr. The necessary guide catheter size for each burr is given in Table 12-1 .
| ROTABLATOR BURR SIZE | LARGE LUMEN GUIDE SIZE |
|---|---|
| 1.25 mm | 5/6 Fr |
| 1.50 mm | 6 Fr |
| 1.75 mm | 7 Fr |
| 2.00 mm | 8 Fr |
| 2.15 mm | 8 Fr |
| 2.25 mm | 9 Fr |
| 2.38 mm | 9 Fr |
| 2.50 mm | 9 Fr |
The calcified lesion may be considered adequately modified when a 1:1 size balloon can be passed through the lesion and fully inflated without any residual waist at ≤14 atmospheres. If a balloon waist persists, additional rotational atherectomy with a larger burr should be considered.
The burr displaces atheroma and fibrocalcific particles without injuring the normal elastic vessel wall. The microparticles created are generally <5 microns in size and are eventually cleared by the reticuloendothelial system. Nevertheless, some patients do suffer from microvascular occlusion and poor or no reflow. To minimize this risk, the procedure should be conducted with continuous pressurized intracoronary infusion (via the Rotablator catheter) of a “rotaflush” solution. This solution usually consists of the proprietary Rotaglide lubricant to increase passage of the burr and reduce heat generation, as well as a calcium-channel blocker (i.e., verapamil or nicardipine) and nitroglycerin to protect the downstream microvasculature. The Rotaglide should not be used in patients allergic to eggs or olive oil, both of which are constituents of the lubricant. Hemodynamic instability may preclude the use of PTRA as infusion of vasoplegic substances in the Rotaflush solution may induce further hypotension.
In addition to the microvascular debris that may occlude the microvasculature, there is a concern that hemolysis from rotational atherectomy elaborates adenosine and other substances that may be detrimental to proper electrical conduction. In combination with the verapamil that constitutes the flush solution, these factors can induce heart block during the procedure. As a result, operators may consider placement of a temporary pacemaker in the right ventricle prior to rotational atherectomy of the RCA or a dominant left circumflex coronary artery. Alternatively, intravenous infusion of aminophylline ± an atropine bolus during runs may be helpful to minimize conduction block.
A helpful online didactic course in using the Rotablator system is also available at http://lms.indegene.com/bsc_rotablator/ .
Clinical Studies of Rotational Atherectomy
After a number of nonrandomized trials suggested a benefit of PTRA compared with percutaneous transluminal angioplasty (PTA) alone, Guerin and colleagues published a pilot randomized trial of PTRA. They evaluated 64 patients (32 in each group) with Type B2 coronary lesions randomized to PTA alone versus PTRA followed by balloon angioplasty. There was no significant difference with respect to Q-wave MI (one in each group), numerically greater non–Q-wave MI in the PTRA group (3 vs. 0), and no significant difference in the primary success rate (93.7% vs. 87.5%), defined as a reduction in stenosis by >20% and residual stenosis <50% without a major complication. Angiographic analysis at 6 months demonstrated no significant difference in restenosis between the two groups (39% vs. 42%).
Subsequently, the Excimer Laser, Rotational Atherectomy, and Balloon Angioplasty Comparison (ERBAC) study randomized 685 patients at a single center to one of these three treatment modalities. The primary endpoint of procedural success (final diameter stenosis <50% and no MACE) was significantly greater in the PTRA group compared with the PTA group (89.2% vs. 79.7%, p = 0.0019), in large part due to a higher likelihood of crossing the lesion and achievement of a final diameter stenosis <50%. Despite this encouraging finding, acute gain was relatively similar between the PTRA and PTA groups (1.25 mm vs. 1.19 mm, p = 0.37), as was the postprocedure diameter stenosis (30% vs. 31%, p = 0.68). There was also a nonsignificant trend toward a greater number of patients with restenosis in the PTRA group (57% vs. 47%, p = 0.14) and a significant increase in TVR in the PTRA and laser groups compared with the PTA group (42% vs. 46% vs. 32%, p = 0.013). Furthermore, the incidence of a MACE was significantly greater in the PTRA group (46% vs. 37%, p = 0.04). The authors’ statement that the role of PTRA can be viewed “optimistically if restenosis is considered a benign disease” appears to overstate the case, though their assertion that PTRA “provides the means to expand the indication for PCI” is reasonable.
The Comparison of Balloon versus Rotational Angioplasty (COBRA) investigators conducted a randomized trial of 502 patients, 250 of whom received routine PTA alone and 252 of whom received PTRA followed by balloon angioplasty. Despite a greater acute net lumen gain in the PTRA group (0.82 mm vs. 0.64 mm, p = 0.008) and better average final diameter stenosis (46% vs. 52%, p = 0.039), the angiographic restenosis rate was equivalent in the two groups (35% vs. 37%, p = 0.658), as was the rate of TLR (29% vs. 25%, p = 0.43). Notably, the need for stent implantation for inadequate PTRA or PTA lumen gain or for bailout was higher in the PTA alone group (9.6% vs. 2.0%). In the contemporary era where stent implantation is the norm, however, it is difficult to consider less stent placement an advantage.
Rotational atherectomy has also been studied for patients with in-stent restenosis (ISR). The Angioplasty versus Rotational Atherectomy for the Treatment of Diffuse In-Stent Restenosis Trial (ARTIST) randomized patients with diffuse ISR to PTA (n = 146) or PTRA (n = 152). The investigators demonstrated a trend toward more periprocedural complications in the PTRA group (composite of death, MI, CABG, PTCA, tamponade, and puncture site complication: 14% vs. 8%, p = 0.09). Furthermore, at 6 months, event-free survival (defined as freedom from death, MI, or clinically driven TLR) was significantly worse in the PTRA group (79.6% vs. 91.1%, p = 0.005). In addition to greater safety than PTRA, PTA alone also demonstrated better procedural efficacy, with a larger net gain (0.67 mm vs. 0.45 mm, p = 0.0019) and fewer patients with restenosis >50% at 6 months (51% vs. 65%, p = 0.039).
In the contemporary era of routine stent placement, initial PTRA has been studied as a strategy to optimize stent deployment and reduce subsequent ISR. The Rotational Atherectomy Prior to TAXUS Stent Treatment for Complex Native Coronary Artery Disease (ROTAXUS) investigators randomized 240 patients equally to DES placement preceded by PTRA versus PTA followed by DES placement. At the conclusion of the procedure, residual stenosis was less (6% vs. 11%, p = 0.04) and acute gain was greater (1.56 mm vs. 1.44 mm, p = 0.01) in the PTRA group. Nevertheless, at 9 months’ angiographic follow-up, there was no significant difference in diameter stenosis or restenosis in the two groups, though in-stent late-lumen loss favored the PTA-alone group (0.31 mm vs. 0.44 mm, p = 0.04). As such, the trial investigators concluded that PTA with provisional PTRA (for uncrossable or undilatable lesions) should remain the default strategy prior to stent placement.
Summary
Despite nonrandomized data and case series that suggest efficacy of PTRA, the totality of clinical trial data does not support the routine use of PTRA compared with PTA either as stand-alone treatment, pretreatment prior to stent implantation, or treatment for patients suffering from ISR. This is confirmed by a recent metaanalysis demonstrating that PTRA does not hold a benefit over PTA alone to reduce restenosis in noncomplex lesions, complex lesions, or ISR ( Figure 12-2 ). Therefore, PTRA should be reserved for lesions that are severely calcified and for which optimal balloon and stent expansion is not possible without plaque modification ( Figure 12-3 ). It may also be necessary for spiculated or severely narrowed lesions that do not allow the passage of balloons and/or stents or lesions that are not dilatable with noncompliant, high-pressure balloons. This is reflected by the 2011 ACC/AHA/SCAI PCI guidelines, which provide a Class IIb recommendation for PTRA in “fibrotic or calcified lesions that might not be crossed by a balloon catheter or adequately dilated before stent implantation” and a Class III recommendation for PTRA “for de novo lesions or in-stent restenosis.”
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