The prevalence and types of coronary artery abnormalities in pediatric patients with Tetralogy of Fallot

Objectives: Tetralogy of fallot (TOF) is one of the most common diseases among cyanotic congenital heart diseases which is associated with 2-23% of coronary artery abnormalities. Pre-operation knowledge the anatomy of coronary arteries in patients with TOF eliminates damage to them during surgery and prevents post-operative complications such as myocardial ischemia and heart failure. Materials and methods: This retrospective study was done on all patients with TOF who were referred for diagnostic catheterization and angiography before total surgical correction from 2006-2016. All patients entered the study and all angiographic views including extreme caudal, LAO cranial , and selective coronary artery angiography were evaluated and reviewed accurately. Results: 332 cases of patients with TOF including from one month to 36 years old were reviewed. The prevalence of coronary artery abnormalities among them was 11.4% (38 from 322 individual). 9.1% and 15.3% of males and females had abnormal coronary anomalies but it was not signicant statically (p-value: 0.064). In 13 of 38 patients with coronary anomalies , coronary arteries crossed right ventricular out ow tract (RVOT)(3.4%). The most common coronary abnormality was origin of the both main coronary arteries from left sinus of Valsalva. Conclusion: Compared the abnormal arteries the patients in our study is signicant (11.4%) and accurate assessment of their courses is necessary before surgery. Single origin of coronary arteries from the left side was the most common nding in our study too.

tree hypoplasia and anastomoses between coronary and branchial arteries. The combined risk of encountering an anomalous coronary artery or a large conus artery crossing the RVOT was reported 10.3% (5).
Knowing the origin and course of coronary arteries is essential for surgeon before starting the operation.
Today in most centers the coronary anatomy is delineated by echocardiography. Rarely in patients with TOF, heart catheterization is used as primary indication to study of coronary pattern (6).
Because of the several types of coronary anomalies in the patients with TOF, this study was done for another investigation of these anomalies in TOF before corrective surgery.

Methods:
This retrospective study was carried on all patients whit TOF who were referred for diagnostic cardiac catheterization and angiography before total surgical correction in 2006-2016.
All patients entered the study and all angiographic views including extreme caudal, LAO cranial and in some cases, selective coronary artery views were evaluated accurately .

Results:
The records of 322 patients with TOF were reviewed. The patients including 318 children and 18 adults were between 1 month to 36 years old (table No. 1). Of 322 patients, 208 were male (62.65%) and 124 were female (37.35%).   Despite the apparent difference between the percentages of coronary abnormalities in two genders, the Pvalue was not signi cance(P-value=0.064).
Coronary arteries crossing RVOT, RCA and LCA originated from LCC and RCC respectively , and single origin of coronary arteries from left side without crossing the RVOT were the most common abnormalities that found in 13, 1 and 24 patients respectively.
Among them with coronary arteries crossing RVOT(13 of 38 (34%)) several varieties were detected; single origin of coronary arteries from left side accompany with LAD passed over the RVOT , single origin of coronary arteries from left side accompany with RCA passed over the RVOT , single origin of coronary arteries from left side accompany with both RCA and LCA passed over RVOT, and also single origin of coronary arteries from right side accompany with LAD passed over the RVOT were found in 3, 2, 2, and 4 patients respectively. In one patient with single origin of coronary arteries from left side LCA passed RVOT.
Despite the normal course of coronary arteries, passing the both RCA and LAD was detected in one patient. (table.3). Discussion: Having knowledge about abnormalities of coronary arteries in patients with TOF is an important key to avoid them getting damage during surgical correction (4-11-12).
Damaging coronary arteries may led to hemi block conduction in patients with dominate right sided coronary circulation or post-operative myocardial infarction (9). As such coronary anomalies may not be seen during operation because of epicardia fat and their position , this pre-operative recognition helps surgeons to get the best strategies before and during surgical correction in patients with TOF.
Although today in most centers the coronary anatomy is delineated by echocardiography, angiography is used as an accurate method before this purpose yet (6,2,10,13,14).
The prevalence of coronary anomalies in paints with TOF was reported in 77 of 607(12%) individual with TOF or TOF like anatomy (14). The other reports by Shirvastava and et al ( (17) on similar patients, showed the same prevalence of coronary anomalies among the patients with TOF(11.4%). In our study, the prevalence of anomalous coronary arteries crossing the RVOT was 3.4% (13 from 38 individuals among the patients with TOF and abnormal coronary artery ) which was lower than the Turkish population (14).
Distribution rate of coronary anomalies based on the sex in our study was similar with Turkish population (66.2% male and 33.8% female in Turkish study (14) versus 62.65% male and 37.35% in our study).
The most coronary artery anomaly which reported by Gupta (17,15,18,19,20 respectively). In our study , single origin of coronary arteries from left side (about 84% of coronary anomalies and 9.6% of all involved individuals) was the most common coronary abnormalities in patients with TOF .

Conclusion:
The prevalence of coronary artery abnormalities among the patients with TOF is signi cant and in order to eliminate damage to coronary arteries during surgical correction, an accurate evaluation of their courses before operation is inevitable.
In our population it seems this prevalence is at the upper range of worldwide references (11.4% versus 2-12% reported in references). Having knowledge about abnormalities of coronary arteries in these patients helps to surgeons to draw a best strategy before operation.

Availability of data and materials
We state that the data used and/or analyzed during the current study are available from the corresponding author on reasonable request. Data sharing is applicable to this article and datasets were generated and analyzed during the current study and data sharing is allowed.

Ethics approval and consent to participate
All procedures performed in this study were in accordance with the ethical standards of the "Research Ethics Committee of Shiraz University of Medical Sciences" and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards. This study was submitted to and approved by the "Research Ethics Committee of Shiraz University of Medical Sciences" .

Consent for publication
This manuscript does not contain any personal data, and the consent for publication is applicable.
Competing interests