Table 2 Study results

Chang 2002 [34]

78 (1988–1992), 268 (1993–1997)

NI

NI

Hospital mortality

No model (volume treated as continuous variable; correlation coefficients)

1988-1992

r = -0.20 (p < 0.01)

1993-1997

r = -0.31 (p < 0.01)

Gutgesell 2002 [35]

1203

NI

NI

Mortality

No model

Low ≤ 50

50%

High >50

40%

Checchia 2005 [42]

801

NI

Survival

Survival

No model

Low ≤4

49%

Low <16

48%

High >4

69%

Medium 16-30

62%

High >30

71%

p = 0.08

Increase by 4% (95% CI 1%-7%) for every 10 additional procedures performed

Linear regression

Trend for mortality p = 0.13

Trend for mortality p = 0.02

Volume treated as continuous variable

Association of risk-unadjusted mortality

Association of risk-unadjusted mortality

r² = NR, p = 0.312

r² = 0.18, p = 0.02

Mean LOS survivors (SD)

Low <16

36.5 ± 32.4

Medium 16-30

28.7 ± 8.4

High >30

29.4 ± 5.7

p > 0.05

Mean TTD (SD)

Low <16

19.6 ± 33.2

Medium 16-30

12.2 ± 9.7

High >30

20.2 ± 9.6

p > 0.05

Median TTD (range)

Low <16

19.2 (1–104)

Medium 16-30

5.4 (1–13)

High >30

7.8 (1–27)

p > 0.05

Berry 2006 [33]

754 (1997), 880 (2000)

Non-teaching vs. teaching

Hospital mortality

NI

Hospital mortality

Logistic regression (teaching status, hospital volume, noncardiac structural anomaly, prematurity, low birth weight, aortic atresia, chromosomal anomaly)

OR 2.6 (1.3 - 5.3)

Low

OR 3.1 (1.1 – 8.3)

Mid-low

OR 2.0 (0.7 – 5.7)

Mid-high

OR 1.0 (0.5 – 1.8)

High

reference

(Categories were determined from quartiles)

Hirsch 2008 [36]

624

Hospital mortality

Mortality

Urban teaching

24.4%

Inverse association p = 0.0001

Logistic regression (volume treated as continuous variable)

Urban non-teach.

32.2%

Rural

34.0%

Unknown

26.6%

Welke 2009 [23]

1154

NI

NI

Mortality

Logistic regression (age, age-for-weight-and-sex z score, interaction between age and age-for-weight-and-sex z score, preoperative stay for more than 2 days; number of prior operations (0, 1, ≤2); renal failure or dialysis, acidosis, circulatory support or shock; preoperative ventilator support or tracheostomy; asplenia, polysplenia, or a22q11 deletion; DiGeorge syndrome; Down syndrome; procedure or procedure group; operation date

Low <150

OR 2.91 (1.98-4.28)

Medium 150-249

OR 1.59 (1.09-2.32)

High 250-349

OR 1.43 (1.06-1.95)

Very high ≥350

Reference

Volume categories for pediatric cardiac surgery

p = 0.002 when hospital volume analysed as continuous variable (test of no volume mortality relationship)

Karamlou 2010 [39]

710

NI

Mortality

Mortality

Hazard regression (Birth weight, age at operation, circulatory arrest time, ascending aortic dimension, reimplantation of the ascending aorta, shunt origin from the aorta)

Increased cases per year (per case): -0.004 ± 0.007 (p = 0.49) [parameter estimate ± SE]

Increased cases per year (per case): -0.005 ± 0.01 (p = 0.38) [parameter estimate ± SE]

McHugh 2010 [40]

1949

NI

NI

Hospital mortality

Logistic regression (?)

Low <20

OR 2.49 (1.51-4.07)

Medium 20-64

OR 1.75 (1.23-2.49)

High >64

Reference

Hornik/Pasquali 2012 [37, 38]

2555

NI

Hospital mortality

Hospital mortality

Logistic regression (all patient characteristics, hospital volume/surgeon volume)

Low ≤5

OR 1.47 (1.01-2.15

Low ≤10

OR 1.37 (0.92-2.05)

Medium 6-10

OR 1.26 (0.88-1.78)

Medium 11-20

OR 1.20 (0.80-1.82)

High >10

Reference

High >20

Reference

OR 1.17 (1.01-1.35) for a twofold decrease in hospital volume

Volume treated as continuous variable

Tabbutt 2012 [41]

549

NI

Renal failure

Renal failure

Logistic regression (anomalous pulmonary venous return, preoperative intubation, heart block, open sternum, volume)

Low ≤5

OR 0.31 (0.09-1.09)

Low ≤15

OR 1.55 (0.53-4.58)

Medium 6 to 10

OR 0.90 (0.28-2.91)

Medium 16 to 20

OR 0.44 (0.14-1.45)

High 11 to 15

OR 0.20 (0.06-0.61)

High 21 to 30

OR 0.32 (0.11-0.91)

Very high >15

Reference

Very high >30

Reference

Log time to first extubation in days

Log time to first extubation in days

Linear regression (gestational age, left atrial decompression, TR preoperatively, duration of regional cerebral perfusion, ECMO, open sternum, duration of open sternum, operations after Norwood procedure, volume)

Low ≤5

0.54

Low ≤15

-0.06

Medium 6 to 10

0.54

Medium 16 to 20

0.31

High 11 to 15

0.40

High 21 to 30

0.21

Very high >15

Reference

Very high >30

Reference

Log length of ventilation in days

Log length of ventilation in days

Linear regression (gestational age, genetic abnormality, preoperative intubation, left atrial decompression, preoperative shock, TR preoperatively, age, open sternum, operations after Norwood procedure, volume)

Low ≤5

0.33

Low ≤15

0.004

Medium 6 to 10

0.27

Medium 16 to 20

0.26

High 11 to 15

0.21

High 21 to 30

0.12

Very high >15

Reference

Very high >30

Referene

Log time hospital LOS in days

Linear regression (birth weight, genetic abnormality, preoperative intubation for shock, TR preoperative, duration of DHCA, operations after Norwood procedure, volume)

Low ≤15

0.16

Medium 16 to 20

0.34

High 21 to 30

-0.03

Very high >30

reference

Sepsis

Logistic regression (gestational age, AS/MS/VD, duration of DHCA, open sternum duration, volume)

Low ≤15

OR 2.28 (1.17-4.47)

Medium 16 to 20

OR 0.94 (0.40-2.19)

High 21 to 30

OR 0.64 (0.33-1.26)

Very high >30

reference