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J Am Heart Assoc. 2015 Jul 13;4(7). pii: e002190. doi: 10.1161/JAHA.115.002190.

New York State: Comparison of Treatment Outcomes for Unruptured Cerebral Aneurysms Using an Instrumental Variable Analysis.

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Section of Neurosurgery, Dartmouth-Hitchcock Medical Center, Lebanon, NH (K.B., R.J.S.).
Department of Neurosurgery, Louisiana State University Health Sciences Center, Shreveport, LA (S.M.).
Geisel School of Medicine at Dartmouth, Hanover, NH (S.C.).
Department of Medicine, Dartmouth-Hitchcock Medical Center, Lebanon, NH (T.A.M.K.) Department of Community and Family Medicine, Dartmouth-Hitchcock Medical Center, Lebanon, NH (T.A.M.K.) The Dartmouth Institute for Health Policy and Clinical Practice, Lebanon, NH (T.A.M.K.).



There is wide regional variation in the predominant treatment for unruptured cerebral aneurysms. We investigated the association of elective surgical clipping and endovascular coiling with mortality, readmission rate, length of stay, and discharge to rehabilitation.


We performed a cohort study involving patients with unruptured cerebral aneurysms, who underwent surgical clipping or endovascular coiling from 2009 to 2013 and were registered in the Statewide Planning and Research Cooperative System database. An instrumental variable analysis was used to investigate the association of treatment technique with outcomes. Of the 4643 patients undergoing treatment, 3190 (68.7%) underwent coiling, and 1453 (31.3%) underwent clipping. Using an instrumental variable analysis, we did not identify a difference in inpatient mortality (marginal effect, 0.13; 95% CI, -0.30, 0.57), or the rate of 30-day readmission (marginal effect, -1.84; 95% CI -4.06, -0.37) between the 2 treatment techniques for patients with unruptured cerebral aneurysms. Clipping was associated with a higher rate of discharge to rehabilitation (marginal effect, 2.31; 95% CI 0.21, 4.41), and longer length of stay (β, 2.01; 95% CI 0.85, 3.04). In sensitivity analysis, mixed-effect regression, and propensity score, adjusted regression models demonstrated identical results.


Using a comprehensive all-payer cohort of patients in New York State with unruptured cerebral aneurysms, we did not identify an association of treatment method with mortality or 30-day readmission. Clipping was associated with a higher rate of discharge to rehabilitation and longer length of stay.


clipping; coiling; instrumental variable; statewide planning and research cooperative system; unruptured cerebral aneurysm

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