Clinical Referral Patterns for Carotid Artery Stenting Versus Carotid Endarterectomy: Results From the Carotid Artery Revascularization and Endarterectomy Registry

Comparison of alternative approaches to trim subjects in the tails of the propensity score distribution

PURPOSE

In nonexperimental comparative effectiveness research, restricting analysis to subjects with better overlap of covariate distributions, hence greater treatment equipoise, helps balance the groups compared and can improve validity. Three alternative approaches, derived from different perspectives, implement restriction by trimming observations in the tails of the propensity score (PS). Across approaches, we compared the relationships between the overlap in treatment-specific PS distributions and the size of the balanced study population after trimming.

METHODS

The three trimming approaches considered were absolute trimming to the range 0.1

RESULTS

The magnitude of the C-statistic strongly predicted (R2 ≥.95) the percent of the balanced study population remaining. The balanced study population was largest under trimming at absolute PS levels, unless the target treatment was uncommon. Fewer than half of original study subjects remained after preference score trimming if C≥.80 and after asymmetric trimming if C≥.85. In examples, trimming improved the precision of estimated risk differences and identified apparent treatment effect heterogeneity in the PS tails where covariate balance was limited. Relative amounts of trimming in examples reflected the simulation results.

CONCLUSIONS

Study populations with high PS C-statistics include only small percentages of subjects in whom valid treatment effects are confidently expected.

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Key Words

• comparative effectiveness
• confounding bias
• equipoise
• methods
• pharmacoepidemiology
• propensity score
• statistical

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MESH Headings

• Bias
• Comparative Effectiveness Research/methods
• Computer Simulation
• Data Interpretation, Statistical
• Models, Statistical
• Propensity Score
• Sample Size

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Grants

• AG056479 NIA NIH HHS
• R21 HD080214 NICHD NIH HHS
• UL1 TR002489 NCATS NIH HHS
• R01 AG056479 NIA NIH HHS
• R01 CA174453 NCI NIH HHS
• R01 HL118255 NHLBI NIH HHS

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Affiliation(s)

Robert J Glynn Pharmacoepidemiology and Pharmacoeconomics, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts
Mark Lunt The Arthritis Research UK Epidemiology Unit, University of Manchester, Manchester, UK
Kenneth J Rothman RTI Health Solutions, and the Department of Epidemiology, Boston University, Boston, Massachusetts
Charles Poole Department of Epidemiology, University of North Carolina, Chapel Hill, North Carolina
Sebastian Schneeweiss Pharmacoepidemiology and Pharmacoeconomics, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts
Til Stürmer Department of Epidemiology, University of North Carolina, Chapel Hill, North Carolina

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Expanding opportunities to understand quality and outcomes of peripheral vascular interventions: The ACC NCDR PVI Registry

Lower extremity peripheral artery disease (PAD) and cerebrovascular disease (CeVD) are prevalent conditions in the United States, and both are associated with significant morbidity (eg, stroke, myocardial infarction, and limb loss) and increased mortality. With a growth in invasive procedures for PAD and CeVD, this demands a more clear responsibility and introduces an opportunity to study how patients are treated and evaluate associated outcomes. The American College of Cardiology (ACC) National Cardiovascular Data Registry (NCDR) Peripheral Vascular Intervention (PVI) Registry is a prospective, independent collection of data elements from individual patients at participating centers, and it is a natural extension of the already robust NCDR infrastructure. As of September 20, 2018, data have been collected on 45,316 lower extremity PVIs, 12,417 carotid artery stenting procedures, and 11,027 carotid endarterectomy procedures at 208 centers in the United States. The purpose of the present report is to describe the patient and procedural characteristics of the overall cohort and the methods used to design and implement the registry. In collecting these data, ACC and ACC PVI Registry have the opportunity to play a pivotal role in scientific evidence generation, medical device surveillance, and creation of best practices for PVI and carotid artery revascularization.

Comparison of Trends and In-Hospital Outcomes of Concurrent Carotid Artery Revascularization and Coronary Artery Bypass Graft Surgery: The United States Experience 2004 to 2012

OBJECTIVES

The aim of this study was to compare trends and outcomes of 3 approaches to carotid revascularization in the coronary artery bypass graft (CABG) population when performed during the same hospitalization.

BACKGROUND

The optimal approach to managing coexisting severe carotid and coronary disease remains controversial. Carotid endarterectomy (CEA) or carotid artery stenting (CAS) are used to decrease the risk of stroke in patients with carotid disease undergoing CABG surgery.

METHODS

The authors conducted a serial, cross-sectional study with time trends of 3 revascularization groups during the same hospital admission: 1) combined CEA+CABG; 2) staged CEA+CABG; and 3) staged CAS+CABG from the Nationwide Inpatient Sample database 2004 to 2012. The primary composite endpoints were in-hospital all-cause death, stroke, and death/stroke.

RESULTS

During the 9-year period, 22,501 concurrent carotid revascularizations and CABG surgeries during the same hospitalization were performed. Of these, 15,402 (68.4%) underwent combined CEA+CABG, 6,297 (28.0%) underwent staged CEA+CABG, and 802 (3.6%) underwent staged CAS+CABG. The overall rate of CEA+CABG decreased by 16.1% (p_trend = 0.03) from 2004 to 2012, whereas the rate of CAS+CABG did not significantly change during these years (p_trend = 0.10). The adjusted risk of death was greater, whereas risk of stroke was lower with both combined CEA+CABG (death odds ratio [OR]: 2.08, 95% confidence interval [CI]: 1.08 to 3.97; p = 0.03; stroke OR: 0.65, 95% CI: 0.42 to 1.01; p = 0.06) and staged CEA+CABG (death OR: 2.40, 95% CI: 1.43 to 4.05; p = 0.001; stroke OR: 0.50, 95% CI: 0.31 to 0.80; p = 0.004) approaches compared with CAS+CABG. The adjusted risk of death or stroke was similar in the 3 groups.

CONCLUSIONS

In patients with concomitant carotid and coronary disease undergoing combined revascularization, combined CEA+CABG is utilized most frequently, followed by staged CEA+CABG and staged CAS+CABG strategies. The staged CAS+CABG strategy was associated with lower risk of mortality, but higher risk of stroke. Future studies are needed to examine the risks/benefits of different carotid revascularization strategies for high-risk patients requiring concurrent CABG.

Early versus late carotid artery stenting for symptomatic carotid stenosis

INTRODUCTION

Early carotid revascularization (≤ 14 days) is recommended for symptomatic carotid stenosis. Carotid artery stenting (CAS) has become an alternative to carotid endarterectomy (CEA); however, safety data on early CAS is controversial. The study aims to compare early versus late CAS, when CAS is performed as a first intention revascularization strategy.

METHODS

A retrospective analysis of all symptomatic patients admitted to our stroke unit who underwent CAS was conducted. Patients were divided between two groups: patients who had undergone CAS within 14 days after symptoms and those who had undergone CAS later. Primary endpoints were ipsilateral ischemic stroke or ipsilateral parenchymal hemorrhage (iPH) at 30 days. The secondary endpoints were major adverse cardiac and cerebrovascular events (MACCE) at the 30-day and at the 12-month follow-up.

RESULTS

One hundred twenty-seven consecutive patients were evaluated. Primary endpoints obtained in the early and late CAS groups were, respectively, ipsilateral stroke (2.0% vs. 2.6%, P = 1.00) and iPH (2.0% vs. 0.0%, P = 0.40). The rates of MACCE between the early and the late CAS groups were, respectively, (7.8% vs. 2.6%, P = 0.21) at the 30-day follow-up, and (12.2% vs. 10.5%, P = 0.77) at the 12-month follow-up.

CONCLUSIONS

In this study, CAS seems to be safe when used as first intention revascularization treatment within 2 weeks of symptoms, if infarcted area is less than one third of the middle cerebral artery territory. Our results need to be confirmed by larger studies.

Outcomes of carotid artery stenting at a high-volume Brazilian interventional neuroradiology center

OBJECTIVES

Carotid artery stenting is an emerging revascularization alternative to carotid endarterectomy. However, guidelines have recommended carotid artery stenting only if the rate of periprocedural stroke or death is < 6% among symptomatic patients and < 3% among asymptomatic patients. The aim of this study is to evaluate and compare clinical outcomes of symptomatic and asymptomatic patients who had undergone carotid artery stenting as a first-intention treatment.

METHOD

A retrospective analysis of patients who underwent carotid artery stenting by our interventional neuroradiology team was conducted. Patients were divided into two groups: symptomatic and asymptomatic patients. The primary endpoints were ipsilateral ischemic stroke, ipsilateral parenchymal hemorrhage and major adverse cardiac and cerebrovascular events at 30 days. The secondary endpoints included ipsilateral ischemic stroke, ipsilateral parenchymal hemorrhage, ipsilateral transient ischemic attack and major adverse cardiac and cerebrovascular events between the 1- and 12-month follow-ups.

RESULTS

A total of 200 consecutive patients were evaluated. The primary endpoints obtained in the symptomatic vs. asymptomatic groups were ipsilateral stroke (2.4% vs. 2.7%, p = 1.00), ipsilateral parenchymal hemorrhage (0.8% vs. 0.0%, p = 1.00) and major adverse cardiac and cerebrovascular events (4.7% vs. 2.7%, p = 0.71). The secondary endpoints obtained in the symptomatic vs. asymptomatic groups were ipsilateral ischemic stroke (0.0% vs. 0.0%), ipsilateral parenchymal hemorrhage (0.0% vs. 0.0%), ipsilateral TIA (0.0% vs. 0.0%, p = 1.00) and major adverse cardiac and cerebrovascular events (11.2% vs. 4.1%, p = 0.11).

CONCLUSIONS

In this retrospective study, carotid artery stenting was similarly safe and effective when performed as a first-intention treatment in both symptomatic and asymptomatic patients. The study results comply with the safety requirements from current recommendations to perform carotid artery stenting as an alternative treatment to carotid endarterectomy.

Fifteen-year experience with carotid artery stenting (from the carotid artery stenting-registry of the Arbeitsgemeinschaft Leitende Kardiologische Krankenhausärzte)

To date only sparse data are available on trends and changes in indications, patient's characteristics, and clinical outcome of patients undergoing carotid artery stenting (CAS) in clinical practice. From February 1996 to December 2010, 6,116 CAS procedures were performed in 5,976 patients at 36 hospitals within the prospective, multicenter CAS registry of the Arbeitsgemeinschaft Leitende Kardiologische Krankenhausärzte. Median age of patients was 71 years, 71.6% were men; a symptomatic stenosis was treated in 50.3% and an embolic protection device (EPD) was used in 82.5% of the patients. The overall hospital mortality or stroke rate was 3.1%. Stroke or in-hospital death occurred in 4.0% in symptomatic patients and in 2.2% in asymptomatic patients. In a logistic regression model, independent predictors of in-hospital death or stroke were heart failure (odds ratio [OR] 2.03, 95% confidence interval [CI] 1.22 to 3.36, p = 0.006), symptomatic stenosis (OR 1.52, 95% CI 1.05 to 2.18, p = 0.03), and age (OR per 10 years 1.46, 95% CI 1.17 to 1.81, p <0.001). The use of an EPD was significantly associated with a lower rate of death or stroke in the registry (OR 0.45, 95% CI 0.26 to 0.78, p = 0.004). From 1996 to 2010, mean age of patients increased by 4.1 years (p <0.001), the proportion of male patients decreased from 82.4% to 70.2% (p = 0.07), the proportion of symptomatic stenoses decreased (84.6% to 24.7%, p <0.001), and the use of EPDs increased from 1.4% to 97.2% (p <0.001). Comparing 2 periods from 1996 to 2003 and 2004 to 2010, a numeric decrease in the in-hospital stroke or death rate was seen in symptomatic (4.7% vs 3.5%, p = 0.11), and in asymptomatic patients (2.9% vs 2.1%, p = 0.27) undergoing CAS, which did not reach statistical significance. In conclusion, the proportion of symptomatic carotid artery stenoses decreased significantly; EPDs established as a standard tool and a numeric decrease of in-hospital stroke or death was seen in asymptomatic and symptomatic patients undergoing CAS in clinical practice over the last 15 years.

An Update on Italian Stroke Organization Guidelines on Carotid Endarterectomy and Stenting

One hundred and fifty-three authors, 45 Italian scientific societies, and two Italian patients' associations participated in drafting the Italian Stroke Organization document, which has become the national guideline for the prevention and treatment of stroke in Italy. For the surgical therapy section of the Italian Stroke Organization document, the main trials on carotid endoarterectomy and stenting were critically reviewed in order to formulate recommendations for these procedures. Recommendations are presented here for the referral of patients to either carotid endarterectomy or stenting on the basis of whether carotid stenosis is symptomatic or asymptomatic.

Increasing role of interventional cardiologists for peripheral vascular disease

Improvements in the design of endovascular devices and technical skills of interventionalists have opened new possibilities for patients with a wide range of peripheral vascular diseases. In lower extremity peripheral artery disease, percutaneous treatments have become the predominant revascularization strategy for simple and complex lesions. Newer generations of stents and drug-coated balloons have demonstrated strong potential in the treatment of femoropopliteal and infrainguinal diseases. One of the most dramatic advances in the recent past has been endovascular repair of thoracic and abdominal aortic aneurysms, which has become the preferred approach in lieu of open surgical repair. Contemporary trials have established the safety and effectiveness of carotid stenting in selected patients with severe stenosis. Endovascular treatments for venous occlusive disease have long been underutilized, but their effectiveness is being increasingly recognized. This review covers new endovascular procedures performed by interventional cardiologists for peripheral vascular diseases.

Association between statin medications and mortality, major adverse cardiovascular event, and amputation-free survival in patients with critical limb ischemia

OBJECTIVES

The aim of this study was to determine the associations between statin use and major adverse cardiovascular and cerebrovascular events (MACCE) and amputation-free survival in critical limb ischemia (CLI) patients.

BACKGROUND

CLI is an advanced form of peripheral arterial disease associated with nonhealing arterial ulcers and high rates of MACCE and major amputation. Although statin medications are recommended for secondary prevention in peripheral arterial disease, their effectiveness in CLI is uncertain.

METHODS

We reviewed 380 CLI patients who underwent diagnostic angiography or therapeutic endovascular intervention from 2006 through 2012. Propensity scores and inverse probability of treatment weighting were used to adjust for baseline differences between patients taking and not taking statins.

RESULTS

Statins were prescribed for 246 (65%) patients. The mean serum low-density lipoprotein (LDL) level was lower in patients prescribed statins (75 ± 28 mg/dl vs. 96 ± 40 mg/dl, p < 0.001). Patients prescribed statins had more baseline comorbidities including diabetes, coronary artery disease, and hypertension, as well as more extensive lower extremity disease (all p values <0.05). After propensity weighting, statin therapy was associated with lower 1-year rates of MACCE (stroke, myocardial infarction, or death; hazard ratio [HR]: 0.53; 95% confidence interval [CI]: 0.28 to 0.99), mortality (HR: 0.49, 95% CI: 0.24 to 0.97), and major amputation or death (HR: 0.53, 95% CI: 0.35 to 0.98). Statin use was also associated with improved lesion patency among patients undergoing infrapopliteal angioplasty. Patients with LDL levels >130 mg/dl had increased HRs of MACCE and mortality compared with patients with lower levels of LDL.

CONCLUSIONS

Statins are associated with lower rates of mortality and MACCE and increased amputation-free survival in CLI patients.

Surgery Versus Stenting in Symptomatic Patients

Symptomatic carotid artery stenosis is an important cause of stroke with significant morbidity and mortality. Revascularization with carotid endarterectomy reduces the recurrence of stroke and until recently was considered the gold standard of therapy. Carotid artery stenting has emerged as an alternative method of revascularization in both high-risk and standard-risk patients. This review appraises the role of surgery versus stenting for patients with symptomatic carotid stenosis.

Carotid artery stenting of a contralateral occlusion and in-hospital outcomes: results from the CARE (Carotid Artery Revascularization and Endarterectomy) registry

OBJECTIVES

The authors sought to study the characteristics and outcomes of patients with contralateral carotid artery occlusions (CCOs) undergoing elective carotid artery stenting (CAS).

BACKGROUND

CCOs are associated with adverse neurological events following carotid endarterectomy.

METHODS

In-hospital outcomes were examined in patients with and without CCO undergoing elective CAS in the Carotid Artery Revascularization and Endarterectomy (CARE) registry. A CCO was defined as a 100% occlusion of the contralateral internal carotid artery. To minimize differences in measured comorbidities, a 3:1 propensity matching analysis was performed comparing 42 clinical and demographic variables between CCO and non-CCO patients from the CARE registry. The primary endpoint was a composite of in-hospital death, nonfatal myocardial infarction, and nonfatal stroke.

RESULTS

Between April 2005 and January 2012, 13,993 eligible patients underwent elective CAS, of whom 1,450 (10%) had CCO. There were 5,500 CAS procedures (1,375 CCO and 4,125 non-CCO) identified in the propensity analysis. The primary composite endpoint occurred in 29 (2.1%) and 107 (2.6%) patients with and without CCO, respectively (adjusted odds ratio: 0.81, 95% confidence interval: 0.53 to 1.23, p = 0.316).

CONCLUSIONS

In the CARE registry, there was no evidence that the presence of a CCO was associated with an increased risk of in-hospital death, nonfatal myocardial infarction, or nonfatal stroke in patients undergoing elective CAS. These findings may have implications on the selection of carotid revascularization procedures for such patients.

Risk prediction for adverse events after carotid artery stenting in higher surgical risk patients

BACKGROUND AND PURPOSE

The goal of carotid artery stenting is to decrease the risk of stroke or other adverse events from carotid artery disease. Choosing a treatment strategy requires patient-specific information regarding periprocedural risk of adverse neurologic events. The aim of this study was to predict individual patient risk after carotid artery stenting in patients at higher risk for carotid endarterectomy.

METHODS

Subjects enrolled in the Stenting and Angioplasty with Protection in Patients at High-Risk for Endarterectomy (SAPPHIRE) worldwide study underwent carotid artery stenting with distal protection. Only patients with at least 1 anatomic or comorbid factor associated with elevated surgical risk were included. Preprocedural factors were used to develop a model and integer-based risk score predicting stroke or death within 30 days. The model was calibrated and internally validated using bootstrap resampling.

RESULTS

Ten thousand one hundred eighty-six patients were included in the analysis. The overall rate of stroke or death was 3.6% at 30 days after carotid artery stenting. Independent predictors of adverse outcomes were increased age (P=0.006), history of stroke (P<0.001), history of transient ischemic attack presentation (P=0.001), recent (<4 weeks) myocardial infarction (P=0.006), dialysis treatment (P=0.007), need for cardiac surgery in addition to carotid revascularization (P=0.005), a right-sided carotid stenosis (P=0.006), a longer carotid plaque (P=0.012), the presence of a Type II or III aortic arch (P=0.035), and a tortuous carotid arterial system (P=0.004). The optimism-adjusted C-statistic was 0.691.

CONCLUSIONS

Commonly collected clinical and anatomic variables can identify patients at high and low risk for stroke or death after carotid artery stenting.

Role of disease risk scores in comparative effectiveness research with emerging therapies

BACKGROUND

Usefulness of propensity scores and regression models to balance potential confounders at treatment initiation may be limited for newly introduced therapies with evolving use patterns.

OBJECTIVES

To consider settings in which the disease risk score has theoretical advantages as a balancing score in comparative effectiveness research because of stability of disease risk and the availability of ample historical data on outcomes in people treated before introduction of the new therapy.

METHODS

We review the indications for and balancing properties of disease risk scores in the setting of evolving therapies and discuss alternative approaches for estimation. We illustrate development of a disease risk score in the context of the introduction of atorvastatin and the use of high-dose statin therapy beginning in 1997, based on data from 5668 older survivors of myocardial infarction who filled a statin prescription within 30 days after discharge from 1995 until 2004. Theoretical considerations suggested development of a disease risk score among nonusers of atorvastatin and high-dose statins during the period 1995-1997.

RESULTS

Observed risk of events increased from 11% to 35% across quintiles of the disease risk score, which had a C-statistic of 0.71. The score allowed control of many potential confounders even during early follow-up with few study endpoints.

CONCLUSIONS

Balancing on a disease risk score offers an attractive alternative to a propensity score in some settings such as newly marketed drugs and provides an important axis for evaluation of potential effect modification. Joint consideration of propensity and disease risk scores may be valuable.

Surgical candidacy and selection biases in nonemergent left main stenting: implications for observational studies

OBJECTIVES

This study sought to characterize reasons for surgical ineligibility in patients undergoing nonemergent unprotected left main (ULM) percutaneous coronary intervention (PCI) and to assess the potential for these reasons to confound comparative effectiveness studies of coronary revascularization.

BACKGROUND

Although both PCI and coronary artery bypass graft surgery are treatments for ULM disease, some patients are not eligible for both treatments, which may result in treatment selection biases.

METHODS

In 101 consecutive patients undergoing nonemergent ULM PCI, mixed methods were used to determine the prevalence of treatment selection dictated by surgical ineligibility and to identify the reasons cited for avoiding coronary artery bypass graft surgery. We then determined whether these reasons were captured by the ACC-NCDR (American College of Cardiology-National Cardiovascular Data Registry) Cath-PCI dataset to assess the ability of this registry to account for biases in treatment selection. Finally, the association of surgical eligibility with long-term outcomes after ULM PCI was assessed.

RESULTS

Treatment selection was dictated by surgical ineligibility in over half the ULM PCI cohort with the majority having reasons for ineligibility not captured by the ACC-NCDR. Surgical ineligibility was a significant predictor of mortality after adjustment for Society of Thoracic Surgeons (hazard ratio [HR]: 5.4, 95% confidence interval [CI]: 1.2 to 25), EuroSCORE (European System for Cardiac Operative Risk Evaluation) (HR: 5.9, 95% CI: 1.3 to 27), or NCDR mortality scores (HR: 6.2, 95% CI: 1.4 to 27).

CONCLUSIONS

Surgical ineligibility dictating treatment selection is common in patients undergoing nonemergent ULM PCI, occurs on the basis of risk factors not captured by the ACC-NCDR, and is independently associated with worse long-term outcomes after adjusting for standard risk scores.

Strategies for asymptomatic carotid artery stenosis

The treatment of asymptomatic carotid artery stenosis (ACAS) has continued to evolve for the past 3 decades. With rapidly advancing technology, the results of old trials have become obsolete. While there has been little change in the efficacy of carotid endarterectomy, there have been vast improvements in both medical management and carotid angioplasty with stenting. Finding the best therapy for a given patient can therefore be difficult. In this article, the authors review the current literature regarding treatment options for ACAS and the methods available for stratifying patients who would benefit from surgical versus medical treatment.