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The Association of Nurse-to-Patient Ratio with Mortality and Preventable Complications Following Aortic Valve Replacement


  • Sources of funding: Nicole Arkin was funded by the MedScholars Grant, Stanford University School of Medicine; Dr. Hernandez-Boussard was supported by grant number K01 HS018558 from the Agency for Healthcare Research and Quality. The content is solely the responsibility of the authors and does not necessarily represent the official views of the Agency for Healthcare Research and Quality.
  • Conflict of interest: The authors acknowledge no conflict of interest in the submission.



To examine hospital resources associated with patient outcomes for aortic valve replacement (AVR), including inpatient adverse events and mortality.

Study Design

We used the Nationwide Inpatient Sample to identify AVR procedures from 1998 to 2010 and the American Hospital Association Annual Survey to augment hospital characteristics. Primary outcomes included mortality and the development of adverse events, identified using standardized patient safety indicators (PSI). Patient and hospital characteristics associated with PSI development were evaluated using univariate and multivariate analyses.


An estimated 410,157 AVRs at 5009 hospitals were performed in the US between 1998 and 2010. The number of procedures grew annually by 4.72% (p = 0.0003) in high volume hospitals, 4.48% in medium volume hospitals (p < 0.0001), and 2.03% in low volume hospitals (p = 0.154). Mortality was highest in low volume hospitals, 4.70%, decreased from 4.14% to 3.73% in medium and high volume hospitals, respectively (p = 0.0002). Rates of PSIs did not vary significantly across volume terciles (p = 0.254). Multivariate logistic regression analysis showed low volume hospitals had increased risk of mortality as compared with high volume hospitals (odds ratio [OR]: 1.42; 95% confidence interval [CI]: 1.01 to 2.00), while hospital volume was not associated with adverse events. PSI development was associated with small hospitals as compared with large (OR: 1.63, 95% CI: 1.16 to 2.28) and inversely associated with higher nurse-to-patient ratio (OR: 0.94, 95% CI: 0.90 to 0.99).


The volume-outcomes relationship was associated with mortality outcomes but not postoperative complications. We identified structural differences in hospital size, nurses-to-patient ratio, and nursing skill level indicative of high quality outcomes. doi: 10.1111/jocs.12284 (J Card Surg 2014;29:141–148)

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