RECENT ADVANCES IN THE SURGICAL MANAGEMENT OF THE SINGLE VENTRICLE PEDIATRIC PATIENT

Although occasional long-term survival without surgical intervention is possible, for most patients with single-ventricle anatomy (SVA), the natural history is dismal. 20 Even patients who manage to survive long term without surgical intervention develop the late sequelae of cyanosis and frequently have depressed ventricular function secondary to volume load and cyanosis. 1 A Fontan procedure is the treatment goal for patients with SVA. The Fontan operation and related procedures, described by Fontan and Baudet, 18 Kruetzer et al, 34 and Glenn, 26 are also known as right heart bypass procedures. Initially, right heart bypass procedures were applied to patients with right heart obstruction, most commonly tricuspid atresia (Fig. 1). These procedures bypass the obstructed right ventricle, connecting systemic venous return directly to the pulmonary arteries. The goal of the Fontan procedure is to connect systemic venous return (superior [SVC] and inferior vena cava [IVC]) with the pulmonary arteries and provide adequate pulmonary blood flow and cardiac output with minimal elevation of the systemic venous pressure. The Fontan procedure separates the systemic and pulmonary venous returns, relieves cyanosis, and decreases the volume load of the single ventricle. The Fontan procedure, therefore, achieves as closely as possible a normal circulatory pattern for patients with SVA. Multiple forms of congenital heart disease are unsuitable for two-ventricle repair, but no one classification system exists. Although Fontan palliation is the ultimate goal for patients with tricuspid atresia, hypoplastic left heart syndrome, and other single ventricles of varying anatomy, these lesions and the outcome of surgical intervention are frequently reported separately in the literature. The particular anatomic subtype is clearly important in forming a plan for neonatal palliation and may have an impact on the long-term outcome as well; however, all patients for whom two-ventricular repair is not possible share common risk factors for early and late survival. For example, systemic outflow obstruction is always a component of hypoplastic left heart syndrome but can also occur with tricuspid atresia, and the surgical intervention may be the same. The anatomic subtype and the particular form of maldevelopment are less important than the identification of anatomy unsuitable for two-ventricle repair. Isolated hypoplasia or atresia of the outlet portion of either ventricle does not rule out a two-ventricle repair. Single-ventricle palliation is required for atresia or significant hypoplasia of either of the atrioventricular valves, severely unbalanced atrioventricular canal, or significant hypoplasia of either ventricle. The term SVA is used for the condition of patients with a functional single ventricle regardless of the anatomic subtype. A standardized, staged approach to the management of patients with SVA ensures better preparation for the Fontan procedure and should improve long-term outcome. Effective neonatal or early infant palliation is the first and most critical stage. During the neonatal or early infant period, the goal is complete relief of systemic obstruction and appropriate limitation of pulmonary blood flow to achieve balanced circulation. Subsequent stages include a bidirectional cavopulmonary anastomosis (BDCPA), which is an anastomosis of the superior vena cava to the confluent pulmonary arteries. Later, the Fontan procedure is completed by connecting the inferior vena cava return to the pulmonary arteries. Following the completion Fontan procedure, central venous pressure is the force that drives pulmonary blood flow. Systemic output is derived from the pulmonary venous return. In this circuit, individual pressure gradients combine to elevate central venous pressure. Severe elevation of the gradient between the systemic vein and the pulmonary atrium results in intolerable elevation of central venous pressure and restrictive ventricular preload, resulting in reduced cardiac output. Risk factors for failure of the Fontan physiology include poor ventricular function with elevated end-diastolic pressure, insufficiency of the atrioventricular valve, elevated pulmonary vascular resistance, pulmonary artery distortion, and stenosis of the systemic venous to pulmonary artery connections. 10,31,32 The goal of the staged approach to patients with SVA is to minimize the risk factors for subsequent Fontan palliation.