Total anomalous pulmonary venous connection

December 31, 2014

Overview

Total anomalous pulmonary venous connection (TAPVC), also known as total anomalous pulmonary venous drainage (TAPVD) and total anomalous pulmonary venous return (TAPVR), is a rare cyanotic congenital heart defect (CHD) in which all four pulmonary veins are malpositioned and make anomalous connections to the systemic venous circulation.(Normally, pulmonary venous return carries oxygenated blood from the lungs to the left atrium where it can then be pumped to the rest of the body). A patent foramen ovale or an atrial septal defect must be present, or else the condition is fatal due to a lack of systemic blood flow.

Symptoms

In the right atrium, oxygen-rich (red) blood from the pulmonary veins mixes with low-oxygen (bluish) blood from the body. Part of this mixture passes through the atrial septum (atrial septal defect) into the left atrium. From there it goes into the left ventricle, then into the aorta and out to the body. The rest of the blood flows through the right ventricle, into the pulmonary artery and on to the lungs. The blood passing through the aorta to the body doesn't have a normal amount of oxygen, which causes the child to look blue.

Symptoms may develop soon after birth. In other patients, symptoms may be delayed. This partly depends on whether the lung veins are blocked as they drain toward the right atrium. Severe obstruction of the pulmonary veins tends to make infants breathe harder and look bluer (have lower oxygen levels) than infants with little obstruction. It's rare for an adult to have uncorrected TAPVC. Patients who survive until adulthood usually have only mild cyanosis and no evidence of blockage. Symptoms include shortness of breath and inability to exercise.

Causes

Sociodemographic findings in patients with total anomalous pulmonary venous connection were similar to those in control subjects. Family history showed no other family members with total anomalous pulmonary venous connection. Noncardiac malformations were present in 9 patients (22%); however, other cardiac and noncardiac malformations were present in 6 first-degree relatives and 7 second-degree relatives of patients with isolated cases (41%). Altogether, a genetic etiology was suspected to contribute to a "failure of targeted pulmonary vein growth" because of the number of multiplex families. In addition, total anomalous pulmonary venous connection has been reported in siblings in other series.

Exposure histories showed possible association of total anomalous pulmonary venous connection with lead or pesticide exposure and raised questions of familial susceptibility to certain environmental teratogens.

Total anomalous pulmonary venous connection frequently occurs in association with asplenia and pulmonary atresia. Overall, one third of patients with total anomalous pulmonary venous connection have a major associated cardiovascular malformation and two thirds of patients have isolated total anomalous pulmonary venous connection.

Diagnosis

Laboratory Studies

Assess and improve (as possible) the oxygenation, acid-base status, and hemogram status in newborns or young infants with total anomalous pulmonary venous connection (TAPVC) in preparation for surgery.

Imaging Studies

Chest radiography

In patients with total anomalous pulmonary venous connection with pulmonary venous obstruction, chest radiographs reveal a normal heart size with a diffuse reticular pattern fanning out from the hilum.
When the pulmonary veins are unobstructed, the heart is enlarged (right atrial and right ventricular enlargement), and pulmonary markings reveal active increase in size of the pulmonary hilar and midzone vessels.

Echocardiography

Echocardiographic findings, which are usually definitive, have been vital in pinpointing the exact cardiac defect. Hyaline membrane disease may demonstrate similar findings initially. In this setting, ECG helps identify right ventricular hypertrophy in patients with total anomalous pulmonary venous connection, especially in premature babies, particularly because premature babies usually have a greater level of left ventricular force.
Echocardiography of the precordium in patients with total anomalous pulmonary venous connection reveals right ventricular and pulmonary artery volume loading with flattened or paradoxic septal motion on M-mode imaging. Apical and subcostal 4-chamber views usually best identify individual pulmonary veins and their confluence in patients with total anomalous pulmonary venous connection. Then, using multiple views, the common pulmonary vein can usually be tracked to its point of entry to the systemic venous system or to the coronary sinus.
Subcostal long- and short-axis views can also help evaluate size and flow patterns across the foramen ovale.
Total anomalous pulmonary venous connection may be difficult to diagnose, especially in an ill newborn on a ventilator, if views of the atrial septum are difficult to obtain or if the common pulmonary vein is small or at an obtuse angle to the left atrial back wall. The addition of color Doppler ultrasonography greatly aids in the diagnosis of individual pulmonary veins and in analysis of the abnormal flow pattern across the atrial septal defect.
Color-flow mapping may be helpful in finding individual pulmonary veins and confirming whether they enter the left atrium. Color-flow ultrasonography may also be used to assess directional flow at the foramen ovale. In patients with total anomalous pulmonary venous connection, flow across the atrial septum predominantly occurs from the right to left.
Altogether, echocardiography with additional color Doppler can help make the diagnosis in the vast majority of patients with total anomalous pulmonary venous connection. In patients with pulmonary inflow obstruction, further diagnostic studies may be needed.
With fetal echocardiography, an attempt should be made to see the individual pulmonary veins, but most consistent diagnostic findings in total anomalous pulmonary venous connection have involved a confluence (chamber) behind the left atrium or a vertical vein.

MRI: MRI serves to confirm the diagnosis in patients with total anomalous pulmonary venous connection (especially in those with associated lung disease).

Selective pulmonary vein or pulmonary artery angiography: This may precisely reveal a vessel's anatomy.

Other Tests

ECG reveals significant right ventricular hypertrophy in most of these patients, usually with a qR pattern in the right chest leads by age 5-7 days. Right atrial enlargement rarely occurs in these younger patients.

Prognosis

If this condition is not treated, the heart will get larger, leading to heart failure. Repairing the defect early provides excellent results if there is no blockage of the pulmonary veins at the new connection into the heart.

Treatment

Medical Care

No catheter-corrective treatment is possible for total anomalous pulmonary venous connection (TAPVC), although atrial septostomy is used in some patients when the foramen ovale is restricted and corrective surgery is delayed for some reason. Catheter placement of a stent has been reported for pretreatment of obstructed vertical vein prior to surgery. If a vertical vein is left patent postoperatively and significant shunt persists it may be possible to close this vessel with an Amplatzer PDA device.

Surgical repair is used as treatment for total anomalous pulmonary venous connection whenever it best serves the individual patient. Stabilizing the patient prior to surgery as much as possible from a cardiovascular and metabolic standpoint is important. In a newborn with obstructive total anomalous pulmonary venous connection, stabilization often involves mechanical ventilation, correction of acidosis, inotropic support, and administration of prostaglandin E1 for patency of patent ductus arteriosus and, in patients with total anomalous pulmonary venous connection type III, for patency of the ductus venous.

Nitric oxide may be useful as a pulmonary dilator postoperatively in patients experiencing episodic pulmonary hypertension that is affecting cardiac output. Reports indicate that magnesium sulfate is a useful pulmonary vasodilator in these patients. Extracorporeal membrane oxygenation (ECMO) may be life saving in some patients. If transesophageal echocardiography is used intraoperatively in infants with pulmonary vein obstruction, waiting for probe insertion until after chest is opened may be safer.

Surgical Care

The goal of surgery is to redirect pulmonary vein flow entirely to the left atrium. In patients with a supracardiac or infracardiac connection, the common pulmonary vein is opened wide and connected side to side to the left atrium. The foramen ovale is closed, and the ascending or descending vein is usually ligated. In a cardiac connection (to right atrium or coronary sinus), the atrial septum is resected partially and a new septum is surgically created, directing pulmonary veins to the left atrium. A coronary sinus may be separately tunneled to the right atrium or left to drain with the pulmonary veins to the left atrium.