Pulmonary atresia with intact ventricular septum

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Pathophysiology

Pulmonary atresia with intact ventricular septum is characterized by complete atresia of the pulmonary valve with varying degrees of hypoplasia of the right ventricle and tricuspid valve. The pulmonary arteries are usually normal in size. With severe right ventricular hypoplasia, coronary artery abnormalities can occur. Right ventricular sinusoids are sometimes present and connect to the coronary arteries. In the presence of right ventricle to coronary artery connections with proximal coronary artery stenoses, myocardial perfusion is dependent upon the pressurized right ventricle. A large atrial septal defect is present in nearly all cases, and pulmonary blood supply is provided by a patent ductus arteriosus. Consequently, obligatory right to left shunting occurs at the atrial level. Ductal closure in the neonate with pulmonary atresia with intact ventricular septum results in severe hypoxia. Prostaglandin E1 infusion is used to maintain patency of the ductus arteriosus prior to surgical intervention. Prostaglandin E1 infusion is life saving and permits stabilization prior to surgical intervention.

Surgical technique

Surgical intervention proposed for patients with pulmonary atresia with intact ventricular septum must be individualized depending on the patient’s specific anatomy. When myocardial blood supply is determined to be dependent upon the right ventricle (right ventricular to coronary artery sinusoids with proximal coronary artery stenosis) right ventricular decompression will result in coronary hypoperfusion and myocardial ischemia. For these patients, transplantation or systemic to pulmonary artery shunting is the first surgical procedure. When coronary artery perfusion is not dependent upon the right ventricle, right ventricular decompression with pulmonic valvotomy or right ventricular outflow tract reconstruction and systemic to pulmonary artery shunting is the surgical approach of choice. Systemic to pulmonary artery shunting is usually required in this subset of patients, as a very poorly compliant,

hypertrophied right ventricle is not usually capable of providing adequate pulmonary blood flow. Right to left atrial level shunting often persists following right ventricular outflow tract reconstruction for the same reason. The ultimate goal when planning surgical intervention for patients with pulmonary atresia with intact ventricular septum is for adequate right ventricular development to occur, allowing ultimate biventricular repair. In some cases, a one and a half ventricle approach is chosen (see One and a Half Ventricle Repair). Severe hypoplasia of the tricuspid valve or right ventricular cavity may preclude biventricular repair, in which case a staged univentricular approach is taken.

Postoperative considerations

Hemodynamic instability is sometimes encountered following right ventricular reconstruction and systemic to pulmonary artery shunting. Right ventricular performance is often depressed immediately following reconstruction. Invasive monitors used include arterial and central venous catheters. An LA line is used when needed for hemodynamic management. LA pressure acts as a surrogate for left ventricular end diastolic pressure, an excellent indicator of left ventricular performance. Non-invasive monitors include NIRS (near infrared spectroscopy) probes to assess adequacy of regional and global perfusion and traditional pulse oximetry. Vasoactive agents might include epinephrine and/or milrinone. Numerous other agents are available and are tailored to the specific needs of the patient, targeting adequate oxygen delivery to the tissues of the body and optimization of cardiac output. Hemodynamic performance gradually improves as right ventricular compliance improves during the first few postoperative days. Bleeding is an uncommon complication encountered following repair of this lesion. Cardiac rhythm disturbance is rarely observed. Delayed sternal closure is sometimes required. Length of hospital stay required following right ventricular reconstruction is variable, but 1 to 2 weeks is average.