Increased mortality at low-volume orthotopic heart transplantation centers: should current standards change?
BACKGROUND
The Centers for Medicare and Medicaid Services (CMS) mandate that orthotopic heart transplantation (OHT) centers perform 10 transplants per year to qualify for funding. We sought to determine whether this cutoff is meaningful and establish recommendations for optimal center volume using the United Network for Organ Sharing (UNOS) registry.


METHODS
We reviewed UNOS data (years 1999 to 2006) identifying 14,401 first-time adult OHTs conducted at 143 centers. Stratification was by mean annual institution volume. Primary outcomes of 30-day and 1-year mortality were assessed by multivariable logistic regression (adjusted for comorbidities and risk factors for death). Sequential volume cutoffs were examined to determine if current CMS standards are optimal. Pseudo R2 and area under the receiver operating curve assessed goodness of fit.


RESULTS
Mean annual volume ranged from 1 to 90. One-year mortality was 12.6% (n = 1,800). Increased center volume was associated with decreased 30-day mortality (p < 0.001). Decreased center volume was associated with increases in 30-day (odds ratio [OR] 1.03, 95% confidence interval [CI]: 1.02 to 1.03, p < 0.001) and 1-year mortality (OR 1.01, 95% CI: 1.01 to 1.02, p = 0.03--censored for 30-day death). The greatest mortality risk occurred at very low volume centers (<or= 2 cases = 2.15 times increase in death, p = 0.03). Annual institutional volume of fewer than 10 cases per year increased 30-day mortality by more than 100% (OR 2.02, 95%CI: 1.46 to 2.80, p < 0.001) and each decrease in mean center volume by one case per year increased the odds of 30-day mortality by 2% (OR 1.02, 95% CI: 1.01 to 1.03, p < 0.001]. Additionally, centers performing fewer than 10 OHTs per year had increased cumulative mortality by Cox proportional hazards regression (hazard ratio 1.35, 95% CI: 1.14 to 1.60, p < 0.001). Sequential multivariable analyses suggested that current CMS standards may not be optimal, as all centers performing more than 40 transplants per year demonstrated less than 5% 30-day mortality.


CONCLUSIONS
Annual center volume is an independent predictor of short-term mortality in OHT. These data support reevaluation of the current CMS volume cutoff for OHT, as high-volume centers achieve lower mortality.
Weiss
Eric S
ES
Department of Surgery, Division of Cardiac Surgery, The Johns Hopkins Medical Institutions, Baltimore, Maryland 21287-4618, USA.
Meguid
Robert A
RA
Patel
Nishant D
ND
Russell
Stuart D
SD
Shah
Ashish S
AS
Baumgartner
William A
WA
Conte
John V
JV
D000046:Academic Medical Centers; D000328:Adult; D002423:Cause of Death; D016001:Confidence Intervals; D003362:Cost-Benefit Analysis; D005260:Female; D006084:Graft Rejection; D006085:Graft Survival; D016027:Heart Transplantation / Q000191:economics / Q000401:mortality* / Q000706:statistics & numerical data*; D017052:Hospital Mortality / Q000639:trends; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D016017:Odds Ratio; D011183:Postoperative Complications / Q000401:mortality; D011237:Predictive Value of Tests; D018570:Risk Assessment; D009927:Tissue and Organ Procurement / Q000191:economics* / Q000706:statistics & numerical data*; D014184:Transplantation, Homologous; D016896:Treatment Outcome; D014481:United States