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77: Tricuspid Atresia and the Functionally Single Ventricle

Carin A. van Doorn; Victor T. Tsang; Marc R. de Leval

Key Concepts

  • Epidemiology

    • Tricuspid atresia is the most common type of functionally single ventricle. Associated cardiac abnormalities are always present and may lead to obstruction of pulmonary or systemic outflow.

  • Morphology and pathophysiology

    • The pulmonary and systemic circulations are in parallel. The degree of hypoxemia depends on pulmonary blood flow, which is determined by the associated cardiac abnormalities and the pulmonary vascular bed, both of which are subject to change over time.

  • Diagnosis

    • Echocardiography provides detailed structural and functional information on the heart, particularly in infants. Cardiac catheterization, magnetic resonance imaging, and computed tomography may be necessary to gather additional information.

  • Treatment

    • Without surgical treatment the majority of patients will die in infancy, either from severe cyanosis or, less commonly, congestive heart failure. The Fontan circulation is widely accepted as the definitive surgical palliation for patients with tricuspid atresia and other anomalies with functionally single ventricles. There are strict selection criteria for the Fontan operation. In particular, preserved ventricular and valvular function and an adequate pulmonary vascular bed are mandatory. Many patients require preliminary operations in infancy to balance pulmonary and systemic circulations. The surgical technique for the Fontan operation has evolved over time.

  • Outcome

    • Operative mortality for suitable Fontan candidates in the current era is approximately 5 percent. Late attrition of the Fontan circulation is a serious clinical problem, and its mechanisms are poorly understood.

Introduction

A wide variety of congenital cardiac lesions lack two well-developed ventricles; from a functional standpoint, they are characterized by a single ventricular chamber that supports both systemic and pulmonary circulations. It is well established that the definitive palliation for these univentricular hearts is the Fontan circulation, whereby the pulmonary and systemic blood flow are placed in series with the single ventricle connected to the systemic circulation. To achieve the Fontan state, many patients need preliminary procedures, either to reduce or to augment pulmonary blood flow.

Definitions and Anatomic Considerations

A truly morphologic univentricular heart is rare; more often there is an additional rudimentary chamber. The most common type of single ventricle is tricuspid atresia, with an incidence of 1 to 3 percent of all congenital heart lesions. In tricuspid atresia there is no direct communication between the right atrium and the right ventricle, and often a dimple or localized fibrous thickening is found at the expected site of the tricuspid valve. The right atrium is large and an interatrial communication is always present. The right ventricle is hypoplastic and lacks an inflow portion, but its trabecular and outflow portions may be well developed. Tricuspid atresia is uniformly associated with other cardiac malformations. A ventricular septal defect (VSD) is usually present. The ventriculoarterial connection can be concordant or, less commonly, discordant (transposition of the great arteries); rarely, there is double-outlet right or left ventricle. Infundibular obstruction to pulmonary blood flow is often present, but this can also be observed at ...

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