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Outcomes of Patients With a History of Coronary Artery Bypass Grafting Who Underwent Orbital Atherectomy for Severe Coronary Artery Calcification
Abstract: Objective. We assess the angiographic and clinical outcomes of patients with a history of coronary artery bypass graft (CABG) surgery who underwent orbital atherectomy for the treatment of severely calcified coronary lesions. Background. The presence of severe coronary artery calcification (CAC) increases the complexity of percutaneous coronary intervention (PCI) and is associated with worse clinical outcomes. Patients with a history of CABG who undergo PCI often have comorbidities and are at higher risk for ischemic complications. Methods. Of the 458 patients who underwent orbital atherectomy, 77 patients (17%) had a history of CABG and 381 (83%) did not. The primary endpoint was rate of 30-day major adverse cardiac and cerebrovascular events (MACCE), comprised of cardiac death, myocardial infarction (MI), target-vessel revascularization (TVR), and stroke. Results. The CABG group had a higher prevalence of hypertension, chronic renal insufficiency, history of PCI, and unstable angina. The primary endpoint was similar in the CABG and non-CABG groups (1% vs 2%; P=.56), as were the individual endpoints of cardiac death (0% vs 2%; P=.27), MI (1% vs 1%; P=.85), TVR (0% vs 0%; P>.99), and stroke (0% vs 0%; P=.65). The rates of angiographic complications and stent thrombosis were similarly low in both groups. Conclusion. Despite a higher-risk baseline profile, patients with a history of CABG had similar angiographic and clinical outcomes compared with patients who had no previous history of CABG. Further studies are needed to clarify the role of orbital atherectomy in these patients.
J INVASIVE CARDIOL 2017;29(10):359-362.
Key words: atherectomy, calcification, coronary artery bypass graft surgery
The presence of severe coronary artery calcification (CAC) increases the complexity of percutaneous coronary intervention (PCI) due to difficulty in predilating lesions and delivering and fully expanding stents.1 Patients with severely calcified lesions who undergo PCI have a higher incidence of adverse cardiac events than those with non-calcified lesions.2 Orbital atherectomy is an effective technique that modifies calcified plaque to facilitate stent delivery and expansion.3
Coronary artery bypass graft (CABG) surgery is commonly performed for patients with complex multivessel coronary artery disease. Survival rates after CABG vary with the population studied, and mortality risks are highly dependent upon postoperative complications, comorbid disease, and the hospital volume of CABG procedures.4-8 Given their medical complexity, there is a concern that post-CABG patients may have a higher risk of complications with procedures involving their grafted coronary vasculature. The outcomes of CABG and non-CABG patients undergoing PCI have previously been compared, but data evaluating the safety and efficacy of orbital atherectomy in these groups are far more limited. This retrospective analysis evaluated the procedural success rates and clinical outcomes of patients with a history of CABG.
Methods
Study population. This was a retrospective analysis of 458 consecutive patients with severely calcified coronary lesions 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). No patient in the registry underwent orbital atherectomy of a bypass graft. Severe CAC was defined as the presence of radio-opacities of the vessel wall on fluoroscopy.3 The Institutional Review Board at each center approved the review of the data.
Device description. After a 0.014˝ ViperWire (Cardiovascular Systems, Inc. [CSI]) traversed the lesion into the distal arterial bed, the orbital atherectomy device (CSI) was advanced just proximal to the lesion while the ViperSlide lubricant (CSI) was infused continuously through the drive shaft. The 1.25 mm crown, which is coated with 30 micron diamonds, is mounted eccentrically and expands laterally while rotating due to centrifugal force.
Procedure and adjunctive pharmacotherapy. Standard techniques were used to perform PCI. A transvenous pacemaker and hemodynamic support device were inserted at the discretion of the operator. After initial activation at low speed (80,000 rpm), high-speed atherectomy (120,000 rpm) was performed at the operator’s discretion if the reference vessel diameter was ≥3 mm. The duration of each pass was ≤20 seconds. The operator had the discretion to predilate the lesion and use intravascular imaging (intravascular ultrasound or optical coherence tomography) as well as choice of stent type, antithrombotic agent, and antiplatelet regimen.
Endpoints. The primary endpoint was 30-day major adverse cardiac and cerebrovascular events (MACCE), defined as the composite of all-cause mortality, myocardial infarction (MI), target-vessel revascularization (TVR), and stroke. MI was defined as recurrent symptoms with new ST-segment elevation or re-elevation of cardiac markers >2x the upper limit of normal. TVR was defined as a repeat revascularization of the target vessel due to restenosis within the stent. Stent thrombosis was defined according to the Academic Research Consortium guidelines.9Major bleeding was defined as intracranial, intraocular, or retroperitoneal hemorrhage; clinically overt blood loss resulting in a decrease in hemoglobin of >3 g/dL; any decrease in hemoglobin of >4 g/dL; or transfusion of ≥2 units of packed red cells or whole blood.10 Patient demographic, angiographic, and procedural data as well as clinical outcomes were recorded on a dedicated PCI database.
Statistical analysis. Continuous variables are expressed as mean ± standard deviation and compared using the Wilcoxon test. Categorical variables are expressed as percentages and compared using the Chi-squared test. A P-value <.05 was considered statistically significant. Statistical analysis was performed with Stata Statistical Software, v. 14.
Results
Baseline demographic characteristics. Of the 458 patients in our study, 77 patients (17%) had a history of CABG and 381 patients (83%) did not (Table 1). The CABG group had a higher prevalence of hypertension (95% vs 85%; P<.01), previous history of PCI (45% vs 34%; P=.047), chronic kidney disease, defined as serum creatinine ≥1.5 mg/dL (29% vs 17%), and presentation with unstable angina (66% vs 47%; P<.01). The CABG group had a higher number of vessels intervened (1.3 ± 0.6 vs 1.2 ± 0.5; P=.04), with increased fluoroscopy time (24 ± 13 min vs 22 ± 19 min; P=.02) (Table 2).
Procedural results. Angiographic complications were low and similar in the CABG patients vs the non-CABG patients: perforation (0% vs 1%; P=.44), dissection (0% vs 1%; P=.30), and no-reflow (0% vs 1%; P=.43) (Table 3).
30-day clinical outcomes. The primary endpoint of MACCE was similar in the CABG patients vs the non-CABG patients (1% vs 2%; P=.56) (Table 4). There were no differences in 30-day rates of death (0% vs 2%; P=.27), MI (1% vs 1%; P=.85), TVR (0% vs 0%; P>.99), and stroke (0% vs 0%; P=.43). Stent thrombosis was also low in both groups (1% vs 1%; P=.66).
Discussion
This subanalysis of patients with a history of CABG and those with no history of CABG revealed no significant differences in clinical outcomes following orbital atherectomy for severe CAC despite worse baseline clinical characteristics.
Approximately 12% of patients who undergo CABG will require repeat revascularization at 10 years and 40% by 20 years due to graft failure and progression of atherosclerosis in native coronary arteries.11 Severe CAC was observed in 33% of patients who underwent CABG in the SYNTAX CABG registry.12 The mortality rate in the patients who underwent CABG was higher if severe CAC was present.13
Patients who have undergone CABG often possess various comorbidities and risks factors increasing their mortality, including the CABG procedures themselves. The ASCERT study of nearly 350,000 isolated CABG patients estimated through Kaplan-Meier that mortality following CABG was 3.2% at 30 days, 6.4% at 180 days, 8.1% at 1 year, 11.3% at 2 years, and 23.3% at 3 years of follow-up.14 Observed predictors of long-term mortality included dialysis-dependent renal failure, insulin-dependent diabetes mellitus, and chronic lung disease (≥ moderate). Unfortunately, coronary artery disease can progress even after successful CABG, and some post-CABG patients eventually require additional PCI with plaque modification. CABG accelerates the atherosclerotic process of the native vessel.15 Modification of calcified plaque with orbital atherectomy is safe and effective in native coronary circulation. Orbital atherectomy can activate platelets and induce thermal injury,16,17 and the extent of this effect in coronary vessels that have undergone accelerated atherosclerosis following CABG is unknown.
There is a paucity of data comparing clinical outcomes in post-CABG vs non-CABG patients undergoing other forms of atherectomy. However, studies have compared these two groups undergoing PCI in general. One analysis reported a higher TVR rate at 1 year following PCI in previous CABG patients compared with non-CABG patients (9.4% vs 2.3%; P<.001).18 This likely can be explained by the higher rate of in-stent restenosis following saphenous vein graft intervention.19 A study noted that among patients undergoing primary PCI for ST-elevation MI, those with a history of CABG were less likely to achieve reperfusion.20 Post revascularization, Thrombolysis in Myocardial Infarction (TIMI) flow was inferior in the CABG group (<TIMI 3 flow in 17% vs 10%; P=.01), as was achievement of acute reperfusion (TIMI 0 in 9% vs 3%; P=.01). This likely is due to the larger atherothrombotic burden in acutely occluded saphenous vein grafts.
Study limitations. This was a non-randomized, retrospective analysis with a short duration of follow-up. Significant differences in several baseline characteristics between both groups may have affected the clinical outcomes. Although this data set is the largest registry of patients who underwent orbital atherectomy, the number of patients who underwent CABG is relatively small. The incidence of periprocedural MI was likely underdiagnosed as cardiac biomarkers were not routinely obtained, yet likely reflects the rate of clinically significant MI. None of the patients underwent orbital atherectomy of a bypass graft. Given the increased risk for distal embolization and no-reflow, orbital atherectomy should not be performed until more data are available, demonstrating its safety in this lesion subset.
Conclusion
A subanalysis of our multicenter registry suggests that a history of CABG does not adversely affect procedural and short-term clinical outcomes in patients undergoing orbital atherectomy. Additional analyses assessing the impact of previous CABG on patients undergoing orbital atherectomy are needed to confirm these findings.
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From 1UCLA Medical Center, Los Angeles, California; 2Northwell Health, Manhasset, New York; and ³St. Francis Hospital — The Heart Center, Roslyn, New York.
Disclosure: The authors have completed and returned the ICMJE Form for Disclosure of Potential Conflicts of Interest. Drs M Lee, E Shlofmitz, and RA Shlofmitz have reported consulting agreements with Cardiovascular Systems, Inc. The remaining authors report no conflicts of interest regarding the content herein.
Manuscript submitted February 23, 2017, provisional acceptance given March 3, 2017, final version accepted March 7, 2017.
Address for correspondence: Michael S. Lee, MD, UCLA Medical Center, 100 Medical Plaza Suite 630, Los Angeles, CA 90095. Email: mslee@mednet.ucla.edu
