Table 1.

Percentage change in odds of death (95% CI; P value) for each extra patient per year in 12 centres in England, including and excluding data for Bristol, according to data for 1991-5 from two data sources

Type of operation	Excluding Bristol data			Including Bristol data
	Hospital episode statistics	Cardiac surgical register		Hospital episode statistics	Cardiac surgical register
All open operations
Children aged <1	−0.38 (−0.71 to −0.04; 0.015)	−0.34 (−0.56 to −0.12; 0.001)		−0.58 (−1.04 to −0.09; 0.01)	−0.42 (−0.69 to −0.13; 0.002)
Children aged ⩾1	−0.20 (−0.81 to 0.46; 0.27)	−0.45 (−1.22 to 0.39; 0.14)		−0.24 (−0.81 to 0.37; 0.22)	−0.47 (−1.20 to 0.31; 0.11)
Open operations (stratified by type of procedure)
Children aged <1	−0.56 (−0.92 to −0.20; 0.0015)	−0.61 (−0.90 to −0.31; <0.0001)		−0.83 (−1.20 to −0.44; <0.0001)	−0.67 (−0.97 to −0.37; <0.0001)
Children aged ⩾1	−0.22 (−0.60 to 0.18; 0.14)	−0.7 (−1.17 to −0.23; 0.002)		−0.25 (−0.61 to 0.13; 0.10)	−0.74 (−1.19 to −0.26; 0.001)
All closed operations
Children aged <1	−0.28 (−1.60 to 1.24; 0.35)	−1.44 (−2.62 to −0.07; 0.02)		−0.28 (−1.68 to 1.36; 0.36)	−1.43 (−2.57 to −0.12; 0.02)
Children aged ⩾1	−9.01 (−9.82 to −4.65; 0.004)	−3.07 (−7.08 to 6.43; 0.2)		−9.17 (−9.84 to −5.61; 0.002)	−2.99 (−6.87 to 5.70; 0.19)