We sought to develop national benchmarks for valve replacement surgery by developing
statistical risk models of operative mortality.
National risk models for coronary artery bypass graft surgery (CABG) have gained widespread
acceptance, but there are no similar models for valve replacement surgery.
The Society of Thoracic Surgeons National Cardiac Surgery Database was used to identify
risk factors associated with valve surgery from 1994 through 1997. The population
was drawn from 49,073 patients undergoing isolated aortic valve replacement (AVR)
or mitral valve replacement (MVR) and from 43,463 patients undergoing CABG combined
with AVR or MVR. Two multivariable risk models were developed: one for isolated AVR
or MVR and one for CABG plus AVR or CABG plus MVR.
Operative mortality rates for AVR, MVR, combined CABG/AVR and combined CABG/ MVR were
4.00%, 6.04%, 6.80% and 13.29%, respectively. The strongest independent risk factors
were emergency/salvage procedures, recent infarction, reoperations and renal failure.
The c-indexes were 0.77 and 0.74 for the isolated valve replacement and combined CABG/valve
replacement models, respectively. These models retained their predictive accuracy
when applied to a prospective patient population undergoing operation from 1998 to
1999. The Hosmer-Lemeshow goodness-of-fit statistic was 10.6 (p = 0.225) for the isolated
valve replacement model and 12.2 (p = 0.141) for the CABG/valve replacement model.
Statistical models have been developed to accurately predict operative mortality after
valve replacement surgery. These models can be used to enhance quality by providing
a national benchmark for valve replacement surgery.