Congenital heart defects comprise a group of structural abnormalities, with an incidence rate of ∼1% of live births.Reference Reller, Strickland, Riehle-Colarusso, Mahle and Correa ¹ Conotruncal heart defects including tetralogy of Fallot affect 15–20% cases of congenital heart defects.Reference Conti, For Grifone and Sarkozy ² Tetralogy of Fallot, the most common type of congenital heart disease, is essentially a right-sided heart disease with characteristic features of ventricular septal defect, right ventricular outflow tract obstruction, aortic dextroposition, and right ventricular hypertrophy.Reference Merante, Myint, Tein, Benson and Robinson ³ To date, mutations in several genes, which are essential for heart development, have been identified in the heart tissues of congenital heart defect patients. In recent years, a lot of associations have been identified between mitochondrial DNA, ∼16.5 kb circular DNA located in mitochondria, and a variety of diseases.Reference Debray, Lambert and Mitchell ⁴ The number of the reports describing these associations has increased exponentially by next-generation sequencing technologies. Owing to the fact that next-generation sequencing has allowed overcoming many limitations of mitochondrial DNA studies, such as estimation of heteroplasmy level and its effects on the severity of mitochondrial diseases, it has provided substantial knowledge about inheritance and structure of mitochondrial DNA.Reference Li, Schonberg, Schaefer, Schroeder, Nasidze and Stoneking ⁵ We report the case of an infant with tetralogy of Fallot with a heteroplasmic T7501C mutation, a G9804A Ala > Thr reported primary mutation of Leber's hereditary optic neuropathy, and a C8481 T Pro > Leu novel missense mutation in the ATP8 gene.

A 7-month-old boy was admitted to our hospital for a history of cyanosis and cardiac murmur since 2 months of age. He was suffering from severe cyanosis with a presence of hypoxic spells for the past 2 months. Physical examination showed severe lip cyanosis, clubbing of the fingers, heart rate of 92 beats/min, regular heart rhythm, systolic murmur at the second and third intercostal spaces left of the sternum, and a weakened pulmonary second review heart sound. The electrocardiogram and chest X-ray were consistent with the diagnosis of tetralogy of Fallot. Evaluation with echocardiography revealed the findings of tetralogy of Fallot: a large ventricular septal defect, dextroposition of the aorta, infundibular stenosis, and right ventricular hypertrophy.

The patient had psychomotor and growth retardation – he could not raise his head and showed no eye following of objects – and was assessed for neurologic pathology with cranial magnetic resonance imaging. Cranial magnetic resonance imaging and ocular fundoscopic examination were normal. Eyesight assessment was planned to be done after surgery. Surgery was performed through a median sternotomy, on a standard aortocaval cardiopulmonary bypass. The patient was cooled to 28°C and an aortic cross-clamp was applied. Antegrade, cold blood cardioplegia was used for myocardial preservation. Total correction of tetralogy of Fallot was done with transatrial closure of the ventricular septal defect with a polytetrafluoroethylene patch, infundibular resection, and right ventricular outflow tract augmentation with a transannular autologous pericardial patch. To further decrease the degree of post-operative pulmonary insuffiency, we divided the pulmonary annulus at the anterior commissure to preserve bicuspid pulmonary valve tissue. The post-operative course was uneventful, and the infant was extubated 12 hours after surgery and discharged on post-operative day 8. After an eventless post-operative period, the patient was referred to the neurology outpatient department for follow-up. Heart tissue samples obtained during surgery with the consent of the parents were examined for mitochondrial DNA mutations.