The role of endovascular expertise in carotid artery stenting: results from the ALKK-CAS-Registry in 5,535 patients

External Validation of Randomized Trial Outcomes Following Carotid Interventions in the Modern Era

An essential prerequisite of randomized controlled trials (RCTs) is “external validation,” that is, results obtained in the “real world” closely replicate those from RCTs. In this respect, contemporary administrative data set registries reporting outcomes after carotid endarterectomy and carotid artery stenting (CAS) have recently reported death/stroke rates that exceed the accepted risk thresholds for intervening. The current article evaluates this controversy and offers reasons why this might continue to happen, namely: (1) difference in interventionists’ competence/experience, (2) patient selection, and (3) advances in CAS technology/technique. As CAS is a continuously evolving technique, the results obtained from patients recruited into the landmark RCTs (as early as the late 1990s) do not reflect contemporary practice. Although RCTs are not always the perfect solution, the process of randomization ensures minimization of selection bias. A possible way forward may be the introduction of prospective, randomized, controlled clinical registries.

Incidence and risk factors of embolized particles in carotid artery stenting and association with clinical outcome

BACKGROUND

One of the mechanisms for periprocedural neurologic events in carotid artery stenting (CAS) is catheter manipulation within the aorta and supraaortic arteries causing plaque embolization. Therefore, the present analysis sought to determine risk factors for embolic particle dimensions and their relationship with adverse clinical events after CAS.

METHODS

Between 1999 and 2015 embolic protection devices (EPD) of a total of 944 CAS procedures were evaluated regarding the occurrence and size of captured particles.

RESULTS

Particles were found in 819 of 944 (87%) EPDs. Larger particles were detected in procedures using open cell stents (150±282μm vs. 107±177μm; p=0.005) and longer stents (≥40mm) (165±315μm vs. 122±215μm; p=0.026). With increasing learning curve, particle size was continually reduced (168±282μm in the first third of the cohort vs. 127±309μm in the second third vs. 108±114μm in the last third; p=0.009). Longer stents and use of Acculink stent were found to be independent predictors for particle diameter. In patients who died or sustained a stroke during long-term follow-up (median 5.5years [IQR 2.6-7.9]) significantly larger particles were captured during CAS compared to those patients with an uneventful follow-up (160±330μm vs. 121±195μm; p=0.047).

CONCLUSIONS

In the vast majority of CAS procedures particles could be retrieved from the EPDs used. Procedural characteristics such as stent type and stent length were associated with larger particles.

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.

Complication rates and center enrollment volume in the carotid revascularization endarterectomy versus stenting trial

BACKGROUND AND PURPOSE

Evidence indicates that center volume of cases affects outcomes for both carotid endarterectomy and stenting. We evaluated the effect of enrollment volume by site on complication rates in the Carotid Revascularization Endarterectomy Versus Stenting Trial (CREST).

METHODS

The primary composite end point was any stroke, myocardial infarction, or death within 30 days or ipsilateral stroke in follow-up. The 477 approved surgeons performed >12 procedures per year with complication rates <3% for asymptomatic patients and <5% for symptomatic patients; 224 interventionists were certified after a rigorous 2 step credentialing process. CREST centers were divided into tertiles based on the number of patients enrolled into the study, with Group 1 sites enrolling <25 patients, Group 2 sites enrolling 25 to 51 patients, and Group 3 sites enrolling >51 patients. Differences in periprocedural event rates for the primary composite end point and its components were compared using logistic regression adjusting for age, sex, and symptomatic status within site-volume level.

RESULTS

The safety of carotid angioplasty and stenting and carotid endarterectomy did not vary by site-volume during the periprocedural period as indicated by occurrence of the primary end point (P=0.54) or by stroke and death (P=0.87). A trend toward an inverse relationship between center enrollment volume and complications was mitigated by adjustment for known risk factors.

CONCLUSIONS

Complication rates were low in CREST and were not associated with center enrollment volume. The data are consistent with the value of rigorous training and credentialing in trials evaluating endovascular devices and surgical procedures.

CLINICAL TRIAL REGISTRATION URL

http://www.clinicaltrials.gov. Unique identifier: NCT00004732.

Endarterectomy or carotid artery stenting: the quest continues part two

BACKGROUND

Although randomized trials on carotid artery stenting (CAS) could not establish its equivalence to carotid endarterectomy (CEA) in patients with symptomatic carotid disease, CAS is rapidly evolving. Data on long-term outcome after CAS from randomized trials have now become available and ongoing, prospectively held registries frequently publish their results in increasing numbers of patients. We have therefore reviewed the currently available literature and provide an update of our previous article on this topic.

DATA SOURCES

PubMed literature searches were performed to identify relevant studies regarding current status of CEA and stenting for symptomatic carotid stenosis.

CONCLUSIONS

The efficacy of CAS in patients with symptomatic carotid artery stenosis remains unclear because of varying results in randomized trials. Although multiple registries do report promising results after CAS, peri-interventional stroke/death rates still exceed those rates currently found after CEA. Therefore, CEA remains the "gold standard" in treating these patients.

[Current guidelines on carotid artery stenting. Critical evaluation]

Scientific data underlying current guidelines on treatment of carotid artery stenosis is subject to interdisciplinary discussion. In particular selective weighting of the randomized European studies leads to conflicting levels of recommendation and levels of evidence, especially when directly comparing guidelines under surgical versus endovascular guidance. Surgical guidelines recommend a limitation of carotid artery stenting (CAS) to symptomatic patients with specific surgical/anatomical disadvantages and/or severe comorbidities. The European Society of Cardiology (ESC) guidelines recommend the use of CAS only in patients at increased surgical risk but at the same time requires morbidity and mortality rates comparable to those of surgical interventions. Even one step further, the American guidelines and specifically the associated comments of the German Society of Cardiology on the above mentioned ESC guidelines put CAS and carotid endarterectomy (CEA) on a par in terms of treatment alternatives, presupposing analogous CEA complication rates. Differential interpretation of the so far inadequate data is a common issue of current evidence-based medicine. The difficulty in conceptualization of new studies concerning the therapy of carotid stenosis lies in the funding these large projects and also on the high patient number required to achieve adequate statistical power. Furthermore, during the estimated long study period substantial changes of current techniques and devices can be anticipated which might render the study results in part outdated by the time of publication. However, as long as no new randomized study results comparing medical, surgical and interventional treatment of carotid stenosis are available, the question on the optimal therapy for patients with carotid artery disease remains unanswered.

Carotid Artery Stenting: Operator and Institutional Learning Curves

Despite rapid growth in the frequency that carotid artery stenting (CAS) is performed, there remain concerns regarding the steep learning curve associated with this procedure. This article reviews the evidence base supporting operator and institutional CAS learning curves and discusses their implications for the establishment and maintenance of competencies. Attempts are made to delineate minimum volume thresholds to attain these goals and means to enhance procedural safety without compromising patient access.

[Carotid artery stenting: is there a volume-outcome correlation?]

Since carotid artery stenting was introduced into clinical practice as an alternative treatment option for significant carotid artery stenosis, several randomized trials have been published with different minimum requirements for the treating interventionalist and therefore different event rates. Analysis of large single center studies and registries has shown a significant decrease in event rates with an increase in experience in carotid artery stenting techniques. The randomized trials with exactly defined minimum requirements including a reasonable number of prior carotid artery interventions showed comparable results between carotid artery stenting and surgical approaches.

[Carotid artery stenting technique]

Over the past 25 years carotid artery stenting (CAS) has emerged as an alternative to carotid endarterectomy (CEA). Most of all younger patients and symptomatic patients with contralateral carotid artery occlusion particularly benefit from CAS. To achieve an optimal result with CAS, patient selection and even more important, knowledge and experience of the interventionist is crucial. The periprocedural complication rate of CAS in large experienced centers is lower (2-3%) than those in randomized trials. Several different devices are now available which allow the procedure to be tailored according to patient anatomy and lesion complexity. Complications like hyperperfusion syndrome and intracerebral bleeding, rupture of side branches of the external or internal carotid artery as well as problems caused by slow flow can be widely avoided by adequate experience.

Safety of carotid stenting (CAS) is based on institutional training more than individual experience in large-volume centres

BACKGROUND

Operator training is a key factor for the safety of carotid stenting (CAS). Whether institutional practice is associated with improved individual operator outcomes is debated.

OBJECTIVE

To evaluate the effect of the institutional experience on outcomes of new trainees with CAS, a retrospective analysis of a prospectively held database was performed.

METHODS

The overall study period, 2004-2012, was divided into two sequential time frames: 2004-April 2006 (leaders-team phase) and May 2006-2012 (expanded team phase). In the first frame, a single leader-operators team that first approached CAS and passed the original institutional learning curve, performed all the procedures; in the following expanded-team phase, five new trainees joined. Institutional CAS training for new trainees was based on a team-working approach including selection of patients, devices and techniques and collegial meetings with critical review and discussion of all procedural steps and imaging.

RESULTS

A total of 431 CAS procedures were performed in the leaders-team phase and 1026 in the sequential expanded-team phase. Periprocedural complication rates in the two time frames were similar: stroke/death (3.0% vs. 2.1%; P = 0.35), stroke (2.8% vs. 2.1%; P = 0.45) major stroke (0.9% vs. 0.6%, P = 0.49), death (0.2% vs. 0%; P = 0.29) during the leaders-team and expanded-team phase, respectively. However, rates of CAS failure requiring surgical conversions (3.7% vs. 0.8%; P < 0.0001) and mean contrast use (91.6 vs. 71.1 ml; P = 0.0001) decreased in the expanded phase. In the expanded-team frame (May 2006-2012), there was no mortality, and stroke rates were comparable between the leader and new operator teams: 2.6% vs. 1.2%; P = 0.17.

CONCLUSIONS

Institutional experience, including instruction on selection of patients and materials best suited for the procedure, is a primary factor driving outcomes of CAS. An effective team-working approach can reliably improve the training of new trainees preserving CAS safety and efficacy.