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Key Concepts

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  • Epidemiology

    • The prevalence of tetralogy of Fallot (TOF) is 0.21 to 0.36 per 1000 live births, accounting for approximately 7 to 10 percent of all congenital heart disease (CHD). 22q11 deletion is seen up to 20 percent of patients with TOF.

  • Morphology

    • The essence of TOF anatomy is the anterocephalad deviation of the muscular outlet septum, which causes right ventricular outflow tract (RVOT) obstruction, override of the aorta, and malaligned ventricular septal defect (VSD). As a result of RVOT obstruction (RVOTO), the patients with TOF have various degree of right ventricular (RV) hypertrophy. The pulmonary valve (PV) is commonly bicuspid and has variable hypoplasia and dysplasia. TOF hearts commonly have multi-level obstruction: at infundibulum, PV, main and branch pulmonary arteries (PAs). Coronary artery anamalies occur in up to 5 percent of patients with TOF.

  • Pathophysiology

    • The pathophysiology of TOF largely depends on the degree of RVOTO: mild RVOTO results in a predominant left-to-right shunt (“pink” TOF), whereas severe RVOTO results in right-to-left shunt and cyanosis. Some neonates with severe RVOTO are dependent on the presence of a patent ductus arteriosus (PDA) for pulmonary perfusion.

  • Clinical features

    • Patients with very mild RVOTO have symptoms of congestive heart failure due to the left-to-right shunt. Those with moderate or severe RVOTO have various degree of cyanosis, that can be episodic (cyanotic spells). In the extreme form of RVOTO, neonates with duct-dependent pulmonary circulation become profoundly cyanotic as the PDA closes.

  • Diagnosis

    • Typically, CXR shows decreased pulmonary vascular markings, upturned apex of the heart, and a pulmonary concavity at the upper left heart border, forming a “boot-shaped heart.” Electrocardiogram shows rightward QRS axis and various degree of RV hypertrophy. Echocardiography is the most important diagnostic modality for delineating anatomy, including nature and degree of RVOTO, aortic override, type of VSD, PV and PAs. Cardiac catheterization, computed tomography (CT), and magnetic resonance imaging (MRI) can be useful in selected cases with unclear anatomy.

  • Treatment

    • Prostaglandin E1 (PGE1) infusion is administered in patients with severe RVOTO and duct-dependent pulmonary circulation. Indication for surgery in the presence of the lesion. Symptomatic neonates are treated with early repair or stenting of RVOT. Patients with no or mild-to-moderate cyanosis typically undergo surgery at 4 to 6 months of age, or when cyanosis gets progressive. In the current era, primary repair is a preferred approach over palliation, with focus on preserving the PV annulus.

  • Outcomes

    • Outcomes are excellent, with operative mortality below 3 percent in contemporary series. One-third of patients require late reintervention for residual RVOTO or VSD, and PV implantation. Late survival is 85 to 87 percent at 30 years after repair.

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Introduction

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Tetralogy of Fallot (TOF) is the most common cyanotic congenital heart disease (CHD). The anatomical essence of TOF is the anterocephalad deviation of the infundibular septum, which causes various degree of right ventricular outflow tract (RVOT) obstruction and subsequent right ventricular (RV) hypertrophy.13 The ...

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