VANCOUVER – The relationship between hospitals’ procedural volume and patient outcomes that has been observed for many cardiovascular interventions and other surgeries does not hold for endovascular mechanical thrombectomy procedures for acute ischemic stroke, according to an analysis of cases during 2008-2011 in the Nationwide Inpatient Sample.
In-hospital mortality and rates for any complications were not associated with high or low endovascular mechanical thrombectomy (EMT) volume at hospitals across the United States in the analysis of 13,502 adult patients hospitalized with a primary diagnosis of acute ischemic stroke and treated with EMT, neurology resident Dr. Abhishek Lunagariya of the University of Florida, Gainesville, reported at the annual meeting of the American Academy of Neurology.
A smaller prior study of 2,749 EMTs done in 296 hospitals in 2008 showed lower mortality in high-volume hospitals that performed 10 or more of the procedures per year (J Stroke Cerebrovasc Dis. 2013 Nov; 22:1263-9).
Of the 13,502 EMTs in the study, 25% occurred at low-volume hospitals performing less than 10 per year. Low-volume hospitals had higher in-hospital mortality than did higher-volume centers performing 10 or more of the procedures per year in an unadjusted comparison (26% vs. 21%). A comparison of a combined endpoint for any complications (in-hospital mortality, intracerebral hemorrhage, and vascular complications) was also significantly in favor of high-volume hospitals (34% vs. 30%).
However, in a multivariate hierarchical model, low-volume hospitals were not associated with higher in-hospital mortality (odds ratio, 0.95; 95% confidence interval, 0.74-1.23) or rate of any complications (OR, 0.96; 95% CI, 0.76-1.21). These analyses were adjusted for age, gender, ethnicity, primary payer, median household income, hospital region/teaching status/location/bed size, Charlson Comorbidity Index, calendar year, and use of intravenous tissue plasminogen activator.
Dr. Lunagariya noted that he and his associates could not adjust the comparisons for National Institutes of Health Stroke Scale scores because they are not recorded in the National Inpatient Sample. They also could not examine what happened to patients after discharge.
Dr. Lunagariya suggested a variety of possible reasons that might help to explain the lack of an association between hospital procedure volume and outcomes after adjustment: the availability of better thrombectomy devices since the smaller 2008 study, lesser operator variability, favorable patient selection, and an increased skill set of operators working at low-volume hospitals.
One audience member noted that some endovascular interventionalists will operate at both high-volume and low-volume hospitals and could account for some of the findings. That indeed might be happening more often and needs to happen more often, Dr. Lunagariya said in an interview, in order to combat the “common belief” that it would be better to wait for a patient to undergo the procedure at a high- rather than low-volume hospital. Patients who receive initial care for stroke at a low-volume hospital but are not stable enough or do not have enough time to be transferred could benefit from EMT if an interventionalist who performs EMT drove there instead, he said.
With even newer devices now available that are thought to be easier to use, Dr. Lunagariya suggested that the similarity in outcomes at low- and higher-volume centers may not change in updated analyses of more recent EMT procedures for ischemic stroke.
The investigators received no funding for the study, and they reported having no financial disclosures.