Transposition of great vessels are usually corrected by an arterial switch operation. This operation is often done during the first week of life as surgical delays lead to deconditioned left ventricle. On the other hand early surgery carries also risks as neonatal physiology may have problems adapting to an intervention under cardiopulmonary bypass, possible pulmonary hypertension. Arterial switch operation between 2008 and 2020 done at our center will be reviewed. Primary outcome will be mortality or severe postoperative morbidity. Patients will be divided in 2 groups according to the presence or absence of the primary outcome. After propensity score matching, they will be analysed according to the timing of operation.

Scientific background and motivation

The transposition of great vessels (TGV) is a congenital heart defect in which the aorta follows the right ventricle and the pulmonary artery follows the left ventricle. At birth, the pulmonary and systemic circulations work in parallel and the communication between them depends on shunts in the cardiac stage (permeability of the Botal hole) or in the supra-cardiac (ducis arteriosus).

It's the most common congenital heart disease and his incidence is estimated between 0.7 and 0.8 per 1000 births. It's a pathology that may be associated with other heart defects, such as interventricular communication (IVC) or pulmonary stenosis, but rarely with a chromosomal abnormality or malformative syndrome.

TGV's manifestation is an isolated cyanosis, refractory to oxygen. And mortality reaches 90% in the first year of life in absence of treatment.

TGV's management has evolved over the last 50 years. First, thanks to the antenatal ultrasound diagnosis, allowing early strategies in postnatal to maintain a shunt between the two circulations (Prostaglandin and Balloon atrial septostomy). Then, by the evolution of corrective surgeries; indeed atrial repair techniques (Senning and Mustard) have given way to the arterial Switch with coronary reimplantation by microsurgery.

When it's possible, the operation takes place during the first week of life. Indeed, it's well established that surgical delay leads to a risk of left ventricle's deconditioned4 and sometimes impaired brain growth. But the risks of a premature surgery are less clear: Operability of the newborn, ability to tolerate an intervention under extracorporeal circulation (ECC), difficulties related to physiological pulmonary arterial hypertension at birth must be considered in the operative indication.

The ideal timing for surgery is still poorly defined. In 2014, Anderson et al showed better results for arterial Switches performed on the third day of life6. On the other hand, Kumar et al, also studied the relationship between operative timing and morbi/mortality of several congenital heart surgeries including the arterial Switch but they found no relationship between them.

Study design

The investigators would like to establish if there is a relationship between the age of the newborn at the time of surgery and postoperative morbi/mortality. Therefore, the investigators want to review all the medical records of children operated on a TGV by the arterial Switch technique at HUDERF between 2008 and 2020. The morbidity/mortality criteria observed will be the same as those usually used in studies conducted on paediatric cardiac surgery at HUDERF:

1. The data of interest will be extracted from a database built up over years summing up the medical records of cardiac operated patients since 2002.
2. Statistics:

2.1. Children will be divided into two groups according to the primary outcome (present or absent). They will be matched using a propensity analysis and then compared in terms of operating time.

2.2. The influence of operative time on the occurrence of the primary outcome will also be analysed by a linear regression technique in which the parameter "operating time" will be considered as a continuous variable.

Inclusion Criteria:

• Newborns with TGV and
• operated at HUDERF between 2008 and 2020 and
• arterial switch operation

Exclusion Criteria:

• Any surgical technique other than the switch operation for TGV
• patients operated before 2008

All children with TGV operated by an arterial switch operation between 2008 and 2020.