This study aims to establish normal coronary artery pulse Doppler flow patterns and velocities using transoesophageal echocardiography (TEE) in patients with a variety of congenital heart disease. This will be accomplished by performing pre-operative and intra-operative TEEs on up to 250 patients undergoing surgery for congenital heart disease.

Little is known about coronary artery flow patterns in children. Invasive and non invasive studies in normal children have demonstrated that coronary artery flow velocities decrease with age and therefore heart rate. 'Normal' flow velocities in the left coronary artery are usually accepted between 0.3-0.6m/sec depending on age of the patient. Less is known about coronary flow patterns and velocities in patients with congenital heart disease. In addition the effects of coronary artery bypass and altered loading conditions may affect coronary flow patterns and velocities and in theory alter short and long term outcomes. This study hopes to is to establish normal coronary artery pulse Doppler flow patterns and velocities using transoesophageal echocardiography (TEE) in patients with a variety of congenital heart disease.

Inclusion Criteria:

• All patients undergoing surgical repair of congenital heart lesions at the Hospital for Sick Children between May 2017 and May 2018.

Exclusion Criteria:

1. Patients with hypoplastic left heart syndrome undergoing Norwood operation or Hybrid procedure
2. Patients who have undergone heart transplantation.
3. Patients were transoespphageal echocardiography is contraindicated (less than 3kg, recent upper gastrointestinal surgery).
4. Operations where TEE is not routinely indicated (patent ductus arteriosus ligation, aortic coarctation repair via a thoracotomy, vascular ring ligations).
5. Patients whose primary reason for surgery is coronary artery stenosis