High Operator and Hospital Volume Are Associated With a Decreased Risk of Death and Stroke After Carotid Revascularization: A Systematic Review and Meta-analysis

Abstract

Objective: To examine the association between operator or hospital volume and procedural outcomes of carotid revascularization.

Background: Operator and hospital volume have been proposed as determinants of outcome after carotid endarterectomy (CEA) or carotid artery stenting (CAS). The magnitude and clinical relevance of this relationship are debated.

Methods: We systematically searched PubMed and EMBASE until August 21, 2017. The primary outcome was procedural (30 days, in-hospital, or perioperative) death or stroke. Obtained or estimated risk estimates were pooled with a generic inverse variance random-effects model.

Results: We included 87 studies. A decreased risk of death or stroke following CEA was found for high compared to low operator volume with a pooled adjusted odds ratio (OR) of 0.50 (95% confidence interval [CI] 0.28-0.87; 3 cohorts), and a pooled unadjusted relative risk (RR) of 0.59 (95% CI 0.42-0.83; 9 cohorts); for high compared to low hospital volume with a pooled adjusted OR of 0.62 (95% CI 0.42-0.90; 5 cohorts), and a pooled unadjusted RR of 0.68 (95% CI 0.51-0.92; 9 cohorts). A decreased risk of death or stroke after CAS was found for high compared to low operator volume with an adjusted OR of 0.43 (95% CI 0.20-0.95; 1 cohort), and an unadjusted RR of 0.50 (95% CI 0.32-0.79; 1 cohort); for high compared to low hospital volume with an adjusted OR of 0.46 (95% CI 0.26-0.80; 1 cohort), and no significant decreased risk in a pooled unadjusted RR of 0.72 (95% CI 0.49-1.06; 2 cohorts).

Conclusions: We found a decreased risk of procedural death and stroke after CEA and CAS for high operator and high hospital volume, indicating that aiming for a high volume may help to reduce procedural complications.

Registration: This systematic review has been registered in the international prospective registry of systematic reviews (PROSPERO): CRD42017051491.

Figure 1

Flowchart detailing the numbers of studies excluded and included at each step of the literature search.

Figure 2

Risk estimates and meta-analysis for the association between CEA operator volume (high vs. low volume) for the outcome procedural death or stroke. Pooled estimates are based on a random effects model. Point sizes of the individual studies are proportional to the standard error of the specific study. Point estimates without confidence intervals were not included in the meta-analyses, and can be found in Appendix Figure 19. The timeframe for the measured outcomes is depicted as follows: no symbol 30-days outcome, * perioperative, # postoperative, $ in-hospital, § not further specified. CEA, carotid endarterectomy; CI, confidence interval; NA, not applicable; OR, odds ratio; RR, relative risk.

Figure 3

Risk estimates and meta-analysis for the association between CEA hospital volume (high vs. low volume) for the outcome procedural death or stroke. Pooled estimates are based on a random effects model. Point sizes of the individual studies are proportional to the standard error of the specific study. Point estimates without confidence intervals were not included in the meta-analyses, and can be found in Appendix Figure 20. The timeframe for the measured outcomes is depicted as follows: no symbol 30-days outcome, * perioperative, # postoperative, $ in-hospital, § not further specified. CEA, carotid endarterectomy; CI, confidence interval; OR, odds ratio; RR, relative risk.

Figure 4

Risk estimates and meta-analysis for the association between CAS operator volume (high vs. low volume) for the outcome procedural death or stroke. No pooled estimates are provided, because only one study per category was included. Point estimates without confidence intervals were not included in the meta-analyses, and can be found in Appendix Figure 21. The timeframe for the measured outcomes is depicted as follows: no symbol 30-days outcome, * perioperative, # postoperative, $ in-hospital, § not further specified. CAS, carotid artery stenting; CI, confidence interval; NA, not applicable; OR, odds ratio; RR, relative risk.

Figure 5

Risk estimates and meta-analysis for the association between CAS hospital volume (high vs. low volume) for the outcome procedural death or stroke. No pooled estimates are provided, because only one study per category was included. The timeframe for the measured outcomes is depicted as follows: no symbol 30-days outcome, * perioperative, # postoperative, $ in-hospital, § not further specified. CAS, carotid artery stenting; CI, confidence interval; NA, not applicable; OR, odds ratio; RR, relative risk.

Figure 6

Funnel plots for all determinant-outcome relations with at least 10 studies. Adjusted or unadjusted in the title refers to the effect estimates under study, i.e. unadjusted/crude relative risks or adjusted odds ratios. Statistically significant asymmetry, indicating statistical evidence for publication bias, was only found within the funnel plot for the reported adjusted associations between CEA hospital volume and death with an Egger’s regression p=0.0012.