Table 1. Benchmark Operation included in this analysis.

Procedure type	Abbreviation	STS-CHSDB Primary Procedure codes
1. VSD Repair	VSD	110=“VSD repair, Patch”
2. TOF Repair	TOF	350=“TOF repair, No ventriculotomy”
		360=“TOF repair, Ventriculotomy, Nontransanular patch”
		370=“TOF repair, Ventriculotomy, Transanular patch”
3. Complete AV Canal Repair	AVC	170=AVC (AVSD) repair, Complete (CAVSD)
4. Arterial Switch	ASO	1110=“Arterial switch operation (ASO)”
5. Arterial Switch + VSD repair	ASO+VSD	1120=“Arterial switch operation (ASO) and VSD repair”
6. Fontan	Fontan	970=“Fontan, TCPC, Lateral tunnel, Fenestrated”
		980=“Fontan, TCPC, Lateral tunnel, Nonfenestrated”
		1000=“Fontan, TCPC, External conduit, Fenestrated”
		1010=“Fontan, TCPC, External conduit, Nonfenestrated”
7. Truncus Repair	Truncus	230=“Truncus arteriosus repair”
8. Norwood	Norwood	870=“Norwood procedure”

The study population includes patients who underwent operations with one of the Primary Procedures listed in Table 1 and met the following inclusionary and exclusionary criteria:

1. Age<18 years

2. Surgical dates: January 1, 2005 – December 31, 2009, inclusive

3. Operations type: “CPB” or “No CPB Cardiovascular” (CPB=cardiopulmonary bypass)

4. The operation was the Index Operation of the admission (i.e. the first operation of a given admission where operation type was “CPB” or “No CPB Cardiovascular”)

5. STS participant had at least 90% complete data for discharge mortality, PLOS, pre-operative risk factors, and non-cardiac abnormalities

6. Fontan: exclude patients age>7 years

7. Truncus: exclude any operation that includes a secondary procedure of “240=Valvuloplasty, Truncal valve” or “250=Valve replacement, Truncal valve”

8. From included participants, patients with missing discharge mortality status or PLOS were excluded from analysis

9. For certain analyses, we restricted inclusion to participants with a certain number of cases, as discussed in the manuscript.