Impact of the Use of Intravascular Imaging on Patients Who Underwent Orbital Atherectomy

Abstract: Objectives. We assessed the impact of intravascular ultrasound (IVUS)/optical coherence tomography (OCT) on outcomes of patients who underwent orbital atherectomy. Background. Intravascular imaging provides enhanced lesion morphology assessment and optimization of percutaneous coronary intervention (PCI) outcomes. Severe coronary artery calcification increases the complexity of PCI and is associated with worse clinical outcomes. Orbital atherectomy modifies calcified plaque, facilitating stent delivery and optimizing stent expansion. The impact of IVUS/OCT on clinical outcomes after orbital atherectomy is unknown. Methods. Of the 458 consecutive real-world patients in our retrospective multicenter registry, a total of 138 patients (30.1%) underwent orbital atherectomy with IVUS/OCT. The primary safety endpoint was the rate of 30-day major adverse cardiac and cerebrovascular events, comprised of death, myocardial infarction (MI), target-vessel revascularization (TVR), and stroke. Results. The IVUS/OCT group and no-imaging group had similar rates of the primary endpoint (1.5% vs 2.5%; P=.48) as well as death (1.5% vs 1.3%; P=.86), MI (1.5% vs 0.9%; P=.63), TVR (0% vs 0%; P=NS), and stroke (0% vs 0.3%; P=.51). The 30-day stent thrombosis rates were low in both groups (0.7% vs 0.9%; P=.82). Emergent coronary artery bypass graft surgery was uncommonly performed in both groups (0.0% vs 0.9%; P=.25). Conclusion. Orbital atherectomy guided by intravascular imaging is feasible and safe. A large prospective randomized trial is needed to determine the clinical benefit of IVUS/OCT during PCI with orbital atherectomy.  

J INVASIVE CARDIOL 2018;30(2):77-80.

Key words: orbital atherectomy, percutaneous coronary intervention, intravascular ultrasound, optical coherence tomography

Coronary artery calcification (CAC) is observed in 38% of lesions with angiography and 73% of lesions with intravascular ultrasound (IVUS).¹ The presence of severe CAC increases the complexity of percutaneous coronary intervention (PCI).² Attempts to dilate a resistant lesion with prolonged, high-pressure inflations can lead to ischemia, dissection, and perforation. Severe CAC can result in suboptimal stent expansion, which may explain the higher risk of in-stent restenosis and stent thrombosis.³

Orbital atherectomy is an effective atheroablative technique that modifies calcified plaque, thereby preparing the lesion to facilitate optimal stent expansion. We previously reported low rates of angiographic complications and adverse clinical events in a multicenter registry of 458 all-comers who underwent orbital atherectomy for severe CAC.⁴ Angiography is limited in its ability to detect CAC. IVUS and optical coherence tomography (OCT) are two imaging techniques that can be used to assess plaque morphology and extent of CAC, and to optimize stent expansion.^5,6 In this multicenter study, we assessed the impact of IVUS/OCT on clinical outcomes in patients with severe CAC who underwent orbital atherectomy.

Methods

In this retrospective analysis of 458 consecutive real-world patients who underwent orbital atherectomy between October 2013 and December 2015 at three centers (UCLA Medical Center, Los Angeles, California; St. Francis Hospital, Roslyn, New York; and Northwell Health, Manhasset, New York), a total of 138 patients (30.1%) also underwent IVUS or OCT (the IVUS/OCT group) and 320 patients (69.9%) did not (the no-imaging group). The institutional review board at each site approved the review of the data. 

The coronary orbital atherectomy device (Cardiovascular Systems, Inc) has been previously described.⁴ The mechanism of action is differential sanding whereby the 1.25 mm crown coated with 30 micron diamonds ablates CAC and flexes away from healthy, compliant tissue, which minimizes injury in areas without CAC. The other mechanism of action is centrifugal force, in which the eccentrically mounted crown laterally expands, ablating plaque around the periphery of the lumen. 

PCI was performed with standard techniques. The decision to image with IVUS or OCT, insert a temporary pacing lead, or use a hemodynamic support device was left to the discretion of the operator. All cases were initially started with low-speed (80,000 rpm) atherectomy. High-speed (120,000 rpm) was only used if the reference vessel diameter was ≥3 mm. Each pass was limited to 20 sec.

All patients received aspirin, which was continued indefinitely. The duration of treatment with a P2Y12 inhibitor was ≥1 month after PCI with a bare-metal stent and ≥12 months after PCI with a drug-eluting stent. The choice of antithrombotic therapy was left to the discretion of the operator. Glycoprotein IIb/IIIa antagonists were only used in bail-out situations.

The primary endpoint was the rate of 30-day major adverse cardiac and cerebrovascular events (MACCE), defined as the occurrence of death, myocardial infarction (MI), target-vessel revascularization (TVR), and stroke. MI was defined as evidence of recurrent ischemia with new ST-segment elevation or re-elevation of cardiac biomarkers to at least twice the upper limit of normal. TVR was defined as repeat revascularization of the target vessel. The Academic Research Consortium definition of stent thrombosis was used.⁷ Severe periprocedural angiographic complications included coronary perforation, dissection, and no-reflow. Demographic and procedural data as well as angiographic and clinical outcomes were recorded in a dedicated PCI database. 

Statistical analysis. Continuous variables are reported as mean ± standard deviation and compared using Student’s t-test. Categorical variables are reported as percentages and compared using Chi-square test. A P-value <.05 was considered statistically significant. Statistical analysis was performed with GraphPad Prism 6 (GraphPad Software, Inc).

Results

The IVUS/OCT and no-imaging groups were well matched with regard to baseline demographic data (Table 1). The prevalence of diabetes was high in both groups (45.7% vs 40.6%; P=.32). The IVUS/OCT group had a higher mean total stent length (38.6 ± 2.0 mm vs 31.6 ± 1.7 mm; P=.01) (Table 2). 

The IVUS/OCT and no-imaging groups had similar rates of perforation (0.7% vs 0.6%; P=.90), dissection (1.5% vs 0.6%; P=.38), and no-reflow (0.7% vs 0.6%; P=.90) (Table 3). The IVUS/OCT and no-imaging groups had similar rates of the primary endpoint (1.5% vs 2.5%; P=.48) as well as death (1.5% vs 1.3%; P=.86), MI (1.5% vs 0.9%; P=.63), TVR (0% vs 0%; P=NS), and stroke (0% vs 0.3%; P=.51) (Table 4). The 30-day rates of stent thrombosis at were similarly low in both groups (0.9% vs 0.9%; P=.82). Emergent coronary artery bypass graft surgery was uncommonly performed in both groups (0.0% vs 0.9%; P=.25). 

Discussion

In the first and only analysis of its kind, the principal finding of our analysis was that the use of IVUS/OCT in patients with severe CAC who underwent orbital atherectomy was feasible and safe. There were no differences in the clinical outcomes at 30 days. 

Suboptimal stent expansion is associated with an increase in adverse clinical events, which is likely due to the higher risk of stent thrombosis and restenosis. Orbital atherectomy is an invaluable tool for preparing the lesion prior to stenting for optimal stent expansion. Intravascular imaging can assess stent expansion and is particularly important in patients with severe CAC given that optimal stent expansion may be difficult in these complex lesions. Imaging allows for identification of suboptimally expanded stents, possibly decreasing the risk of ischemic complications with postdilation. 

Intravascular imaging may also potentially improve outcomes by facilitating the selection of appropriate stent diameter and length. In our study, the IVUS/OCT group had a higher

total stent length. One explanation is that intravascular imaging may have resulted in the detection of more extensive plaque, leading to the use of longer stents.

Intravascular-imaging guided orbital atherectomy did not lower the MACCE rate. The rate of 30-day MACCE associated with orbital atherectomy was low, potentially making it difficult to demonstrate a benefit with IVUS/OCT. The short duration of follow-up may also explain the lack of benefit with intravascular imaging. A longer duration of follow-up is needed to determine if IVUS/OCT-guided orbital atherectomy can lower the rates of stent thrombosis and in-stent restenosis. 

Several studies have reported on the clinical benefit of PCI guided by IVUS to reduce ischemic events, possibly due to a larger postprocedure minimal luminal diameter.^8-11 In the MAIN-COMPARE registry, assessment with IVUS prior to PCI showed a lower mortality rate at 3 years in patients with unprotected left main coronary artery disease.¹² In a study of 291 calcific lesions in 198 patients, IVUS showed favorable clinical outcomes for optimizing PCI with bioresorbable scaffold in the presence of calcium.¹³

Cases that are particularly likely to benefit from imaging-guided PCI are those in which there is a lower likelihood of achieving a large minimum stent area, such as in patients with severe CAC. PCI guided by IVUS/OCT may improve clinical outcomes by identifying suboptimally expanded stents due to severe CAC, which increases the risk of periprocedural complications and adverse cardiac events including stent thrombosis and in-stent restenosis. The incidence of failure in deploying drug-eluting stents has been reported to be 5.8% in severe CAC lesions compared to 1.8% in non-calcified lesions.¹⁴ Although orbital atherectomy is an invaluable tool for modifying complex lesions with severe CAC, aggressive postdilation may still be needed to optimally expand the stent. IVUS has been shown superior to angiography alone in evaluating CAC.¹ 

In addition to accurate assessment of lesion severity when angiography is not diagnostic, intravascular imaging is helpful in determining which patients would benefit from atherectomy, which is indicated when the arc of calcium is ≥270°. Furthermore, IVUS/OCT provides a high-resolution tomographic view of vessels that allows improved demarcation of the distribution, composition, and morphology of arterial plaque. 

In the ILUMIEN III: OPTIMIZE PCI trial, OCT-guided PCI was non-inferior to IVUS-guided PCI in terms of the quality of stent expansion, as defined by the achieved minimum stent area.¹⁵ Furthermore, both imaging strategies provided better post-PCI minimum stent area compared to standard PCI without imaging. OCT-guided PCI resulted in significantly fewer untreated edge dissections compared to both the IVUS and angiography groups.

Study limitations. This was a small, retrospective study with a short follow-up duration, and was not powered to assess for outcomes with intravascular imaging. Quantitative coronary angiography and assessment of IVUS/OCT measurements were not performed to determine if IVUS/OCT-guided orbital atherectomy resulted in an increase in minimal luminal diameter and a reduction in residual stenosis. The study was not powered to demonstrate a reduction in the number of stents used per procedure, which has both cost and procedural benefits. The decision to perform IVUS/OCT was left to the discretion of the operator. Data on whether intravascular imaging resulting in further postdilation were not recorded. 

Conclusion

Orbital atherectomy guided by IVUS/OCT is safe and effective, with low rates of MACCE and angiographic complications. The potential benefits of IVUS/OCT-guided orbital atherectomy must be balanced with the increased cost of the device and longer procedural time. A large, prospective, randomized trial is needed to determine the clinical benefit of IVUS/OCT during PCI with orbital atherectomy. 

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From the ¹UCLA Medical Center, Los Angeles, California; ²Northwell Health, Manhasset, New York; and ³St. Francis Hospital, Roslyn, New York.

Disclosure: The authors have completed and returned the ICMJE Form for Disclosure of Potential Conflicts of Interest. Drs Lee, E. Shlofmitz, and R. Shlofmitz report honoraria from Cardiovascular Systems, Inc. The remaining authors report no conflicts of interest regarding the content herein.

Manuscript submitted May 8, 2017, provisional acceptance given May 18, 2017, final version accepted June 1, 2017.

Address for correspondence: Michael S. Lee, MD, Associate Professor of Medicine, 100 Medical Plaza, Suite 630, Los Angeles, CA 90095. Email: mslee@mednet.ucla.edu