Original Contribution

In-Hospital Outcomes of Rotational Atherectomy in High-Risk Patients With Severely Calcified Left Main Coronary Artery Disease: A Single-Center Experience

Ashwat S. Dhillon, MD;  Meena R. Narayanan, MD;  Han Tun, MBBS, MPH;  Antreas Hindoyan, MD; Ray Matthews, MD;  Anilkumar Mehra, MD;  David M. Shavelle, MD;  Leonardo C. Clavijo, MD, PhD 


Abstract: Background. Severe coronary artery calcification is a challenge for percutaneous coronary intervention (PCI), particularly in left main coronary artery disease (LM-CAD). Rotational atherectomy (RA) is a useful tool for modification of calcified plaque prior to PCI. We report our experience with RA for severely calcified LM-CAD. Methods. From January 2008 to January 2017, all patients who underwent RA-assisted LM-PCI were evaluated. The study population included both protected and unprotected LM-CAD patients. Clinical characteristics and in-hospital outcomes were collected retrospectively. In-hospital outcomes included post-PCI myocardial infarction, stroke, death, emergency coronary artery bypass graft surgery, and urgent repeat PCI. Angiographic success was defined by residual stenosis <20% and presence of TIMI 3 flow. Results. Fifty-five consecutive patients who underwent RA-assisted PCI of LM-CAD were identified (mean age, 73.0 ± 10 years; 64% male). Mean left ventricular ejection fraction was 37.5 ± 15.7%. Fifty-one patients (93%) had multivessel disease and 39 patients (71%) underwent RA-assisted LM-PCI with use of a mechanical support device. The median largest burr size used was 1.5 mm. The mean number of LM stents implanted was 0.95 ± 0.3. The mean LM stent diameter and length were 3.7 ± 0.3 mm and 15.8 ± 7.5 mm, respectively. Intravascular ultrasound was used to assess vessel size and stent apposition in 20 patients (36.0%). Angiographic success was obtained in all patients (100%). Conclusion. Despite technical challenges, RA of the LM coronary artery can be performed safely and is associated with a high rate of angiographic success.

J INVASIVE CARDIOL 2019;31(4):101-106. (Epub 2019 January 15).

Key words: left main coronary artery, mechanical circulatory support, percutaneous coronary intervention, rotational atherectomy


Severely calcified left main coronary artery disease (LM-CAD) represents a challenging lesion subset for percutaneous coronary intervention (PCI). Complex calcified lesions portend a poorer long-term prognosis compared to non-calcified lesions.1 Inadequate predilation of calcified lesions leads to suboptimal stent expansion and increased rates of in-stent restenosis and stent thrombosis.2 Additionally, repeated and prolonged balloon inflation in the LM may cause global ischemia, leading to electrical and hemodynamic instability. Rotational atherectomy (RA) allows for plaque modification by using a diamond-encrusted elliptical burr, which preferentially ablates calcified plaque over healthy arterial tissue.3 RA safely facilitates stent implantation with high rates of procedural success.4,5 Unlike balloon angioplasty, RA results in a more compliant plaque and a smoother lumen, leading to improved stent expansion and apposition. Furthermore, RA leads to greater acute lumen gain, possibly decreasing the risk of in-stent restenosis and stent thrombosis.3 However, no randomized controlled trials have demonstrated superiority of RA when compared to balloon angioplasty or stent implantation. The ROTAXUS (Rotational Atherectomy to Taxus Stent Treatment for Complex Native Coronary Artery Disease) trial assessed late lumen loss and did not find a significant benefit of RA prior to drug-eluting stent implantation when compared to standard balloon predilation.6 However, patients with unprotected LM disease were excluded from the study and only a few patients with protected LM-CAD were included.6 Currently, there are limited data on the use of RA for LM-CAD.7-12 We report our experience and outcomes for patients with heavily calcified LM-CAD who underwent RA.

Methods

We performed a retrospective analysis of patients who underwent RA for severely calcified LM-CAD at our institution from January 2008 to January 2017. Significant LM-CAD was defined as a >50% stenosis of the LM. Our study cohort included patients with protected and unprotected LM lesions. Protected LM-CAD was defined by at least one patent graft to the left coronary system. Baseline clinical, angiographic, and procedural characteristics, in-hospital outcomes, and clinical follow-up data were collected. In-hospital follow-up data included days in intensive care unit (ICU), acute kidney injury (AKI), major bleeding (as defined by the Blood Academic Research Consortium [BARC] criteria),13 postprocedural myocardial infarction (MI), stroke, and all-cause death. Non-fatal postprocedural MI was defined as elevation of troponin >3x the baseline, with or without ST-segment elevation and/or development of Q-waves on electrocardiogram (ECG). In-hospital event rates of death, stroke, and target-lesion revascularization (TLR) were assessed. Death was adjudicated as cardiac or non-cardiac. Stent thrombosis was defined as proposed by the Academic Research Consortium (ARC).14 The logistic EuroScore II was used to assess surgical risk.15 The Syntax score was used to quantify severity of CAD in patients without prior bypass surgery (low, 0-22; intermediate, 23-32; and high, ≥33).16 Cardiogenic shock was defined by the presence of signs of peripheral hypoperfusion and with an invasive systolic blood pressure <90 mm Hg or when vasoactive agents were needed to maintain systolic blood pressure ≥90 mm Hg. Use of percutaneous left ventricular assist device and intra-aortic balloon pump (IABP) was assessed, and we compared outcomes based on the type of mechanical circulatory support (MCS) used. Furthermore, since this was a retrospective analysis of procedures done over a 10-year period, we performed a subgroup comparison of outcomes in procedures done within the first 5 years (2008-2012) and the second 5 years  (2013-2017). All patients in our study underwent RA of the LM as a primary plaque preparation strategy prior to stent deployment. Other approaches, such as scoring balloons, cutting balloons, or orbital atherectomy, were not used.

Procedural details. All procedures were performed via the transfemoral route. RA was performed using the Rotablator device (Boston Scientific) at a rotational speed of 140,000-180,000 rpm, with care to avoid decelerations of >5000 rpm. The burr size was selected to reach a burr/vessel ratio of 0.5 (maximum ratio of 0.7 if needed). RA was performed as a primary lesion preparation tool prior to stent deployment in this patient population. A continuous intracoronary infusion containing verapamil, nitroglycerin, and unfractionated heparin was used to prevent slow-flow. Temporary pacing was done at the discretion of the operator. During the intervention, all patients received intravenous unfractionated heparin (70-100 IU/kg) to maintain the activated clotting time of 250-300 sec (or 200-250 sec if glycoprotein IIb/IIIa inhibitors were administered). Postprocedural troponin was routinely measured in all patients. Antiplatelet regimens included aspirin and thienopyridines (75 mg clopidogrel or 10 mg prasugrel daily) for a minimum of 12 months after PCI. Intravascular ultrasound (IVUS), MCS devices, and stent types (bare-metal or drug-eluting) were used according to the operator’s discretion. Angiographic success was defined as final residual diameter stenosis of <20% and presence of TIMI 3 flow. Procedural success was defined as angiographic success without death, stroke, acute postprocedural MI in the cardiac catheterization laboratory, emergency coronary artery bypass surgery, or urgent repeat revascularization.

Statistical analysis. Statistical analysis was performed using SAS software, version 9.4 (SAS Institute). Descriptive analysis was used. Continuous variables with normal distribution are shown as mean ± standard deviation. Categorical variables are expressed as numbers and percentages. Chi-square test or Fisher’s exact test were used to compare categorical variables and Student’s t-test was used to compare continuous variables. All probabilities are two-sided, and a P-value of ≤.05 was considered significant.

Results

Baseline clinical characteristics are shown in Table 1. Fifty-five consecutive patients (mean age, 73.0 ± 10.1 years; 63.6% male) who underwent RA-assisted LM-PCI between the years 2008 to 2017 were included in the study. Eighteen patients (32.7%) had prior coronary artery bypass graft surgery and 13 patients (23.6%) had prior PCI. Fifty-one patients (92.7%) had triple-vessel disease. Clinical presentation of the patients was as follows: 11 patients (20%) presented with stable angina, 15 patients (27.3%) with unstable angina, 27 patients (49.1%) with non-ST elevation MI (NSTEMI), and 2 patients (3.6%) with ST-elevation MI (STEMI). Both of the STEMI patients and 5 of the NSTEMI patients presented in cardiogenic shock. The mean Syntax score was 33.2 ± 8.9%, and the mean surgical mortality risk of the patient cohort according to the EuroScore II scale was 13.6%.

Angiographic and procedural characteristics. The procedural and LM lesion characteristics are presented in Table 2. In our study group, a total of 22 patients (40%) had LM bifurcation lesions involving the ostia of both the left anterior descending (LAD) and left circumflex (LCX) coronary arteries (Medina classification 1,1,1). The median burr size was 1.25 mm. Stents were placed in the LM proximal to bifurcation in 5 patients (9%); stents crossed over from the LM into the LAD or LCX in 36 patients (65.5%); 7 patients (12.7%) underwent simultaneous kissing stents from LM to LAD and LCX; the step-crush technique was employed in 3 patients (5.5%); and T-stenting was done in 3 patients (5.5%). One patient received only balloon angioplasty to the LM and LCX. Drug-eluting stent implantation was performed in 51 patients (92.7%) and bare-metal stents were implanted in 3 patients (5.5%). IVUS was used in 20 patients (36.3%) to assess stent apposition. One patient came to the cardiac catheterization laboratory with extracorporeal membrane oxygenation (ECMO) already in place for salvage PCI. There were no cases of burr entrapment, flow-limiting coronary artery dissection, coronary artery perforation, or cardiac tamponade in our patient population. Angiographic success rate was 100%, with no cases of coronary perforation or no-reflow.

Mechanical circulatory support. Eleven patients (20%) underwent PCI with intra-aortic balloon pump (IABP) support, 26 patients (47.3%) with percutaneous left ventricular assist device (pLVAD) support, and 2 patients (3.6%) with ECMO support (Table 2). We also assessed the type of MCS used in protected and unprotected LM cases; in the unprotected LM group, pLVAD support was used in 22 patients (58%) and IABP was used in 9 patients (24%) (Table 3).

In-hospital outcomes. In-hospital outcomes are shown in Table 4. In-hospital morbidity (defined as a composite of AKI and major bleeding) occurred in 8 patients (14.5%). Cardiac death occurred in 2 patients (3.6%) and TLR was performed in 1 patient (1.8%). Although postprocedural troponin elevation (>3x baseline) occurred in 11 patients (20%), only 3 patients required repeat intervention. Of these 3 patients, there was 1 case of definite acute stent thrombosis, with the patient developing ventricular fibrillation a few hours after PCI. The patient was taken back to the catheterization laboratory emergently, and underwent successful revascularization. The other 2 patients underwent successful staged intervention of residual LCX disease. In terms of in-hospital mortality, 3 patients died (2 cardiac, 1 non-cardiac) during the index hospitalization, for an in-hospital mortality rate of 5.4%. Cause of death was refractory cardiogenic shock despite successful PCI in 1 patient. The second patient presented to our facility in cardiogenic shock (emergent transfer from an outside hospital after failed coronary artery bypass graft surgery) on ECMO for salvage PCI. Although salvage PCI was performed successfully, the patient died 3 days post PCI with multisystem organ failure. The third patient died 37 days after PCI due to sepsis and respiratory failure; this was considered a non-cardiac death. When comparing the type of MCS used during PCI, there were no differences in length of hospital stay, in-hospital morbidity, or death (Table 5). Comparing the first half (2008-2012) with the second half (2013-2018) of the study period, we found no significant differences in outcomes (Table 6).

One-year follow-up. Although this retrospective study primarily sought to assess in-hospital outcomes, we did have limited 12-month follow-up data available. At 12-month follow-up, 6 patients (11%) presented to the hospital with angina; on repeat coronary angiogram, they were found to have evidence of in-stent restenosis of the LM, requiring repeat PCI.

Discussion

Severe coronary calcification poses a unique challenge to successful PCI. Significant calcification is associated with lower angiographic success since it may impede stent delivery and stent expansion. RA is an effective tool for debulking heavily calcified coronary plaque. Although the main indication for RA is the treatment of moderate-severely calcified coronary artery plaque, RA is also indicated for complicated bifurcation lesions, chronic total occlusions, and ostial lesions with bulky plaque.2,17-20 Other indications for RA are when there is failure to adequately predilate with standard, non-compliant, or scoring/cutting balloons, and/or failure to cross the stenosis with the primary device.21 Currently, the use of RA during PCI is infrequent, with a recent analysis from the National Inpatient Sample database reporting atherectomy usage rate of 3.15% nationwide.22 The reasons for low RA use include the risks of no-reflow, vessel dissection, profound hypotension during the procedure, the possible entrapment of burr, and vessel perforation.3,23 Despite these procedural risks, adequate lesion preparation is of paramount importance for severely calcified LM-CAD prior to stent deployment, and as such, every effort should be made to debulk calcified LM stenosis to achieve angiographic success after PCI. In our catheterization laboratory, RA is performed by experienced operators, and appropriate premedication (intracoronary nitrate administration, dual-antiplatelet therapy, intracoronary calcium-channel blockers) is provided. In addition, we are supported by staff who are well versed in setting up the RA apparatus in an efficient manner.

A few observational studies have been recently published demonstrating the safety and feasibility of RA in LM-PCI, with in-hospital mortality rates reported to range from 0.0%-8.8%, which is comparable to our study.7-12 We had no complications, such as burr entrapment or vessel perforation, relating to RA-assisted LM-PCI. Although there were 3 in-hospital deaths (5.5%), none were procedure related and 2 deaths occurred in patients with prior MI with refractory cardiogenic shock. All patients in our study had severely calcified LM-CAD with a high mean Syntax score, and were considered high risk for surgical revascularization. In our study, we found that PCI with RA for LM-CAD demonstrated 100% angiographic success.

It is notable that a significant postprocedural elevation of troponin was observed in 20% of our study cohort. Although we have reported this postprocedural elevation in troponin as a postprocedural MI, only 1 of the patients with the significantly elevated troponin post PCI had clinical or electrocardiographic evidence of acute coronary syndrome (acute ST with immediate successful repeat PCI). It has been postulated that significant elevation in troponin after RA may be secondary to microembolization of debris in the coronary vasculature and/or thermal injury.24 Although we had a higher rate of post-PCI troponin elevation than the incidence reported in recent studies (which reported a periprocedural MI rate of 2.0%-5.8%), it did not appear to affect in-hospital mortality in our patient cohort.7,9

Park et al showed that systematic IVUS guidance during LM-PCI is associated with improved long-term clinical outcomes.25 Despite this, the use of IVUS guidance during LM-PCI varies from 2.9%-73.0% in the literature.8,10,11 In our cohort, 36% of patients had IVUS-assisted PCI. The low rate of IVUS usage was likely secondary to the technical issues associated with introducing the IVUS catheter in severely calcified vessels (and/or vessel tortuosity), as well as operator preference.

The rate of IABP support use for LM-PCI in our study population was 20%, which is comparable to the reported range of 7.5%-20.0% in prior studies.7-12 Twenty-six patients (47%) underwent RA of the LM with pLVAD support, and ECMO support was used in 2 patients. Given the high mean Syntax score, high-risk EuroScore II, and a mean left ventricular ejection fraction of 37% in our study population, it is reasonable that a majority of the RA-assisted LM-PCI in this patient cohort was performed with MCS. However, no significant correlation was seen between type of MCS support (IABP vs pLVAD) and clinical outcomes. In addition, there were no differences in the type of stenting technique and rates of ISR at 12 months, although follow-up data were limited. Larger, more extensive studies are needed to reach a reliable conclusion regarding the utilization of MCS support for RA-assisted LM-PCI.

Study limitations. Our study is a single-center, retrospective, observational study with a small sample size, and may inherently contain selection bias. However, the study population represents a complex and high-risk patient population. IVUS was used in less than half of our study cohort, leading to a deficiency in obtaining morphologic information of the target vessel. We do not have data available for whether IVUS was used before, after, or both before and after PCI. Many operators advocate the use of IVUS in all LM interventions.26,27 The reasons for the relatively low use of IVUS in the current study remain unclear and could not be determined by retrospective chart review. Our study population included patients with protected and unprotected LM-CAD, limiting the generalizability of the immediate in-hospital outcomes. Assessment of coronary artery calcium was made using fluoroscopy in a majority of the patients, and with the help of IVUS guidance in 36% of the patients. As such, we did not have a standardized assessment method across different operators. We do not have detailed postdischarge follow-up data, and therefore mainly assessed in-hospital outcomes in our study population.

Conclusion

RA for severely calcified LM coronary artery disease can be performed safely with a high rate of angiographic success. However, since only limited observational data are available, prospective randomized clinical trials are needed to adequately evaluate the benefit of RA prior to PCI of heavily calcified LM-CAD.

References

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From the Division of Cardiovascular Medicine, Keck School of Medicine, University of Southern California, Los Angeles, California.

Disclosure: The authors have completed and returned the ICMJE Form for Disclosure of Potential Conflicts of Interest. The authors report no conflicts of interest regarding the content herein.

Manuscript submitted September 30, 2018, provisional acceptance given October 10, 2018, final version accepted October 25, 2018.

Address for correspondence: Ashwat S. Dhillon, MD, Division of Cardiovascular Medicine, Keck School of Medicine, 1510 San Pablo Street, Suite 322, Los Angeles, CA 90033. Email: Ashwat.Dhillon@med.usc.edu

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