Effects of institutional volumes on operative outcomes for aortic root replacement in North America.
OBJECTIVE
Hospital procedure volume has been strongly associated with postoperative mortality for a number of complex cardiovascular procedures. Although not yet described, a similar relationship might be expected for surgical procedures involving the aortic root and/or ascending aorta. The present study sought to evaluate the relationship between the volume of aortic root replacement procedures and the operative results for centers in North America.


METHODS
Patient-level data for 13,358 elective aortic root and aortic valve-ascending aortic procedures performed from 2004 through 2007 were obtained from 741 North American hospitals participating in the Society of Thoracic Surgeons Adult Cardiac Surgery Database. Marginal logistic regression modeling was used for risk adjustment. The hospital procedure volume was the primary predictor variable. Patient demographics, comorbid conditions, and operative characteristics were included as the predictor variables for risk adjustment. The primary outcome measures included unadjusted operative mortality and adjusted odds ratio for mortality.


RESULTS
The preoperative patient risk profiles were similar at all center volume levels, and the overall unadjusted operative mortality was 4.5%. The unadjusted operative mortality increased with decreasing case volume, from 3.4% in the highest volume centers to 5.8% in the lowest volume centers. Whether hospital volume was assessed as a categorical or continuous variable, its relationship with the adjusted odds ratio for mortality was nonlinear. A negative association was seen between the hospital procedural volume and adjusted odds ratio for mortality (P < .001) that was most pronounced among hospitals performing fewer than 30 to 40 procedures annually.


CONCLUSIONS
Patients undergoing elective aortic root or combined aortic valve-ascending aortic surgery at North American hospitals that performed fewer than 30 to 40 of such procedures annually have greater risk-adjusted mortality than those undergoing surgery in higher volume hospitals. Causative factors for this inverse association between hospital volume and mortality deserve additional analysis.
Society of Thoracic Surgeons Database, Durham, NC, USA. gchad.hughes@duke.edu
G Chad
GC
Hughes
Yue
Y
Zhao
J Scott
JS
Rankin
John E
JE
Scarborough
Sean
S
O'Brien
Joseph E
JE
Bavaria
Walter G
WG
Wolfe
Jeffrey G
JG
Gaca
James S
JS
Gammie
David M
DM
Shahian
Peter K
PK
Smith
D001011:Aorta / Q000601:surgery*; D001021:Aortic Valve / Q000601:surgery*; D019917:Blood Vessel Prosthesis Implantation / Q000009:adverse effects / Q000401:mortality; D006348:Cardiac Surgical Procedures / Q000009:adverse effects / Q000401:mortality; D015897:Comorbidity; D017558:Elective Surgical Procedures; D005260:Female; D017052:Hospital Mortality; D061847:Hospitals, High-Volume / Q000706:statistics & numerical data; D006801:Humans; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D009656:North America; D016017:Odds Ratio; D011183:Postoperative Complications / Q000209:etiology / Q000401:mortality; D019984:Quality Indicators, Health Care / Q000706:statistics & numerical data; D018570:Risk Assessment; D012307:Risk Factors; D013997:Time Factors; D016896:Treatment Outcome