Tetralogy of Fallot (TOF) is a congenital defect caused due to the improper development of the right side of the heart. It is a complex of four different cardiac defects, that include ventricular septal defect, narrowing of the pulmonic outflow tract (right ventricular infundibular stenosis), right ventricular hypertrophy, and aortic valve positioned to override the right ventricle. The overall effect of these defects is that the blood flow to the lungs in restricted, leading to low levels of oxygen (hypoxia) in the blood. Cyanosis follows, and the baby develops a bluish tint in the skin, fingers, and lips.
TOF is the most common of all cyanotic congenital heart defects, and can be seen in one out of every 1000 babies with congenital heart disease. TOF can be clearly diagnosed using ECG, chest X-ray, echocardiogram, and cardiac catheterization. Immediate treatment to manage hypoxia in infants involves administration of beta blockers like propanolol, or morphine and phenylephrine. However, corrective surgery is required early in life to conclusively treat the disease. Surgery includes widening of the narrowed pulmonary valve, and closure of the ventricular septal defect.
Al-Arrayed (personal communication, 20.1.2007) reported a 6-year-old Bahraini boy born to non-consanguineous family with Holt-Oram syndrome. The boy also had features of congenital cyanotic heart disease, tetralogy of Fallot, and an inactive gastro-esophageal reflux.
Der Kaloustian et al. (1985) reported a consanguineous Christian Maronite Lebanese family in which two sisters were affected with TOF with pulmonary valve atresia.
Maghur et al. (2002) conducted a retrospective study of 94 children who underwent modified Blalock-Taussig shunts (MBTS) in Mesallata Cardiothoracic Centre between 1992 and 1998. Tetralogy of Fallot (TOF) comprised the majority of cases while the remaining included tricuspid atresia, pulmonary atresia, univentricular heart complex, and others.
Ould Zein et al. (2006) described the epidemiological profile of congenital heart diseases in 84 Mauritanian children. Ventricular septal defect (17%), tetralogy of Fallot (13%) and pulmonary stenosis (12%) were the predominant pathologies.
Subramanyan et al. (2000) conducted a study to determine the incidence and pattern of congenital heart disease (CHD) in Oman. Of the 992 patients found to have CHD, 9.6% were diagnosed with Tetralogy of Fallot. This was greater than the percentage of TOF among CHD patients in other countries like Saudi Arabia (4.5%).
In a separate study by Venugopalan et al. (2002) to evaluate the distribution of heart diseases in 2652 children less than 13 years in Oman assessed in an open-access echocardiography service during a 5-year period, 21 (2.5%) had tetralogy of Fallot. Additionally, Sawardekar (2005) conducted a study to establish the prevalence of major congenital malformations in children born during a 10-year period in an Omani hospital in Nizwa. Of the 21,988 total births in the hospital, two patients were born with Tetralogy of Fallot. Similarly, Jaiyesimi and Baichoo (2007) undertook a study to determine the patterns of congenital cardiac malformations in Omani patients with Down syndrome. A total of 110 children with Down syndrome were evaluated. A total of 76 malformations were detected, including two cases of tetralogy of Fallot.
Alshehri (2005) studied the pattern of all major congenital anomalies in the Asir region between the years 1997 and 2002. Of the total of 691 neonates born with anomalies, 13 were diagnosed with tetralogy of fallot. This constituted 11.4% of neonates with circulatory system anomalies. [Alshehri MA. Pattern of major congenital anomalies in southwestern Saudi Arabia. Bahrain Med Bull. 2005; 27(1).]
Almawazini and AlGhamdi (2011) screened 2610 children from Albaha region with congenital heart disease (CHD). Of these, 27 patients (4.7%) were found to have TOF.
El Kalla et al. (1992) reported an infant with multiple congenital anomalies, tetralogy of Fallot, and Karyotype 45,X,t(Y;18)(q12;11.2). The infant's anomalies are consistent with chromosome 18p deletion syndrome, except for the exceptional severity of the heart defect.
In 1998, Al Talabani et al. studied the pattern of major congenital malformations in 24,233 consecutive live and stillbirths at the maternity hospital in Abu Dhabi, between 1992 and 1995. A total of 401 babies (16.6/1,000), including 289 Arabs, were seen with major malformations, including six cases with tetralogy of Fallot.
Hosani and Czeizel (2000) evaluated the pilot dataset [March-May 1998] of the UAE National Congenital Abnormality Registry (NCAR). A total of 4,861 births were recorded in this study period, with a birth prevalence of total congenital anomalies being 30.3/1,000 births. Tetralogy of Fallot was identified in six neonates, resulting in an incidence rate of 1.23/1,000 births.