• To predict vulnerable patients for aortic root dilatation in TOF patients using CT as a reliable imaging modality, thus aiding early intervention, and identifying those who will require strict follow-up.
• To assess the prevalence of TOF patients who developed aortic root dilatation, and those who were complicated with dissection, AR, and aneurysm, through collecting data from a large center (Aswan Heart Centre).
• To investigate the relationship between age at repair and the diameter of aortic root.

Tetralogy of Fallot (TOF) occurs in approximately 3 to 5 of every 10,000 live births and is the most common cyanotic congenital heart defect and it exhibits four main features. These features are pulmonary stenosis, right ventricular hypertrophy, overriding aorta and ventricular septal defect. Moreover, since the survival of patients with congenital heart diseases has improved significantly in recent decades, long-term complications should be monitored cautiously. One of these complications is aortic root dilatation, attributed to increased and altered flow through the overriding aorta and an uneven sharing of conotruncal tissue between the aorta and pulmonary artery, particularly in patients who have not undergone early repair.

Despite the concern that TOF patients may harbor aortopathy that can lead to aortic regurgitation, aortic aneurysms, and, potentially, aortic dissection, the scope of the problem remains uncertain. Prevalence estimates of aortic root dilatation have ranged from 15% to 87% with the use of various criteria. Moderate to severe aortic regurgitation (AR) has also been reported in up to 12.5% of adults with TOF and dilated aortic roots. The incidence of aortic dissection and surgical intervention remains unknown. Moreover, features associated with aortic dilatation are not fully understood. Therefore, correlating and predicting vulnerable patients and identifying possible risk factors for aortic root dilatation in TOF patients, will enable more cautious follow-up and earlier intervention, thus decreasing possible morbidity and mortality.

Inclusion Criteria:

• All patients with TOF who either underwent or have not yet had surgical correction.
• All patients with Fallot-type DORV.
• Patients should have survived until discharge and have at least one echocardiography and CT with full data related to one or more anatomic subcomponents of the aortic root, either before surgery or during follow-up, regardless of specific duration post repair.

Exclusion Criteria:

- Patients who have contraindication for conducting cardiac CT scan. For instance, dye sensitivity, pregnancy, CKD, in addition to patients who have factors that interfere with CT image quality as metallic objects within the chest (e.g. Pacemaker).

Sample size was calculated using Epi- Info7. Based on aortic dilatation is found in 84.6 in follow up CT [12] With a confidence limits 5% and a confidence level of 80% the minimum patients required for this study is 77 cases.