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Enrollment volume effect on risk factor control and outcomes in the SAMMPRIS trial
David Chiu1, Richard P Klucznik2, Tanya N Turan2
1From Houston Methodist Hospital (D.C., R.P.K., C.D.M., L.B.K.), Weill Cornell Medical College, TX; Medical University of South Carolina (T.N.T., M.I.C.), Charleston; Emory University Rollins School of Public Health (M.J.L., A.N., B.F.L., J.M.), Atlanta, GA; Washington University School of Medicine (C.P.D.), St Louis, MO; State University of New York (D.F.), Stony Brook; and National Institute of Neurological Disorders and Stroke (S.J.), National Institute of Health, Bethesda, MD. dchiu@tmhs.org.
Insights
Physician experience, measured by patient volume, significantly impacts medical therapy outcomes in stroke prevention. High-volume centers achieved better risk factor control and lower event rates in the SAMMPRIS trial medical arm.
Area of Science:
- Neurology
- Clinical Trials
- Cardiovascular Medicine
Background:
- Physician experience and patient volume are known to influence surgical outcomes.
- Limited data exist on the impact of these factors on medical therapy effectiveness.
- The Stenting and Aggressive Medical Management for the Prevention of Recurrent Ischemic Stroke (SAMMPRIS) trial provides a valuable dataset to investigate this.
Purpose of the Study:
- To evaluate the effect of high- vs. low-enrolling sites on patient outcomes in the SAMMPRIS trial.
- To determine if physician experience, indicated by patient volume, influences the efficacy of medical therapy for stroke prevention.
Main Methods:
- Comparison of Kaplan-Meier curves for the primary endpoint (stroke or death) between high-enrolling (≥12 patients) and low-enrolling (<12 patients) sites.
- Analysis of risk factor control (LDL cholesterol, systolic blood pressure) using Fisher exact test.
- Study included both stenting and medical cohorts of the SAMMPRIS trial.
Main Results:
- In the stenting group, no significant difference in primary endpoint rates was observed between high- and low-enrolling sites.
- In the medical group, high-enrolling sites showed significantly lower rates of the primary endpoint compared to low-enrolling sites (p=0.0005).
- Patients at high-enrolling sites achieved better control of LDL cholesterol (64% vs 49%) and systolic blood pressure (70% vs 59%) in the combined treatment groups.
Conclusions:
- Higher patient volume at clinical trial sites is associated with improved outcomes in the medical management of patients at risk for recurrent ischemic stroke.
- Physician experience, reflected by site enrollment volume, appears to be a critical determinant of success in medical therapy.
- These findings underscore the importance of experience in optimizing medical therapy for secondary stroke prevention.
Objective:
The role of physician experience and patient volumes on the outcome of surgical or endovascular procedures has been well-studied but there are limited data on how these factors affect the outcome of medical therapy.
Methods:
In the stenting and medical cohorts of the Stenting and Aggressive Medical Management for the Prevention of Recurrent Ischemic Stroke (SAMMPRIS) trial, we compared Kaplan-Meier (K-M) curves for the primary endpoint (any stroke or death within 30 days of enrollment or ischemic stroke in the territory beyond 30 days) using the log-rank test and the percentages of patients achieving target levels for primary and secondary risk factors during the study using Fisher exact test between patients at high-enrolling (≥12 patients) vs low-enrolling (<12 patients) sites.
Results:
In the stenting group, the K-M curves for the primary endpoint were similar at high-enrolling sites and low-enrolling sites (p = 0.93) with rates of 13.5% vs 14.7% at 30 days and 19.0% vs 20.6% at 2 years. In the medical group, the K-M curves differed between high-enrolling sites and low-enrolling sites (p = 0.0005) with rates of 1.8% vs 9.8% at 30 days and 7.3% vs 20.9% at 2 years. The percentages of patients who achieved targets for low-density lipoprotein cholesterol and systolic blood pressure at high- vs low-enrolling sites in both treatment groups combined were 64% vs 49% (p = 0.003) and 70% vs 59% (p = 0.026), respectively.
Conclusions:
High-enrolling sites in SAMMPRIS achieved better control of primary risk factors and much lower rates of the primary endpoint than low-enrolling sites in the medical group, suggesting that experience with medical management is an important determinant of patient outcome.
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