Double inlet left ventricle (DILV) is a serious congenital heart disease which occurs in approximately 5 to 10 of every 100 000 births.
It results in the presence of a single pumping chamber, which is morphologically the left ventricle. This chamber receives all of the blood from the body through the right and the left atria. As a result, oxygenated blood from the lungs entering the heart through the left atrium mingles with deoxygenated blood entering the heart from the venous circulation through the right atrium. This mixture of poorly oxygenated blood is pumped by the single left ventricle to the body as well as to the lungs.
DILV may be associated with other heart anomalies such as coarctation of the aorta and pulmonary atresia. These children may require emergency or early surgery to ensure their survival till further staged surgery can be performed to improve the circulation to an acceptable level.
The timing of surgery depends on the symptoms, complications, other abnormalities present and the general condition of the child. The earliest surgery may consist of pulmonary banding if too much blood is going to the lungs producing breathlessness and pulmonary congestion. This narrows the caliber of the artery, and reduces pulmonary blood flow. Conversely, an aorto-pulmonary bypass may be needed in those cases where too little blood is reaching the lungs.
Staged surgery is done starting from about 4-6 months, with the bidirectional Glenn (hemi-Fontan) procedure which routes blood from the superior vena cava into the right pulmonary artery, bypassing the right atrium. The superior vena cava is the great vein which carries blood from the entire upper half of the body into the right atrium of the heart. However, this procedure does not completely relieve the cyanosis.
The Fontan procedure is the final stage of surgery, performed at 18-36 months. Here the inferior vena cava, which drains venous blood from the lower part of the body to the right atrium, is also anastomosed to the right pulmonary artery. This is done through the creation of a lateral tunnel, by introducing a baffle into the right atrium to produce a tubular space between it and the right atrial wall. This provides an unobstructed route for venous blood to reach the lungs and can grow with the growth of the child. A smaller area of the right atrial wall is exposed to high pressures, leading to lower chances for atrial dilatation. The rationale for this procedure was the occurrence of supraventricular arrhythmias, brought on by progressive atrial dilatation.
A later modification was by routing the blood from the inferior vena cava to the right pulmonary artery outside of the right atrium through an extracardiac conduit. The right atrium is closed off completely from the rest of the heart. This can only be done when the artificial channel used can be large enough to accommodate an adult’s venous return, because the graft cannot grow with the child. In this technique, however, there is no atrial dilatation at all.
The Fontan procedure greatly improves the hemodynamics of the patient and allows systemic venous blood to flow directly to the lungs. Systemic hypoxemia is corrected, and ventricular volume overload is abolished. It also prevents the progressive dilatation of the right atrium which precipitates refractory arrhythmias and eventual heart failure. The baby is no longer cyanotic following the achievement of Fontan circulation.
In an analysis of patients in whom the Fontan procedure was performed in the early years following its introduction, the palliative nature of the operation remains evident. Increasing surgical refinements of technique, materials and patient selection have led to a greater increase in the quality of life. There was a lower chance of complications or failure of the Fontan circuit, and a greater long-term survival at 20 years following the surgery, with the use of the lateral tunnel and extracardiac Fontan techniques.
In one recent study, 94% of patients were still alive at 15 years after the creation of a lateral tunnel, in contrast to the earlier survival rate of 65% for patients who had an atriopulmonary connection created, in the initial Fontan era.
Even with successful surgery, the operation is to be regarded as palliative. Some restriction of activity must be imposed and regular follow-up with a cardiologist is mandatory. Medications including anticoagulants, antiarrhythmics, digitalis and anti-hypertensives such as the ACE inhibitors must usually be continued throughout life. Further surgeries may also be required.
Anti-endocarditis prophylaxis is required, and complications such as clubbing, pneumonia, arrhythmias and congestive heart failure are to be watched for throughout life. Failure of the circuit is another complication which may occur at any time. These occur especially in patients with less than optimal risk factors. However, most patients with low risk factors achieve an acceptable quality of life with good treatment and follow-up.
Reviewed by Yolanda Smith, BPharm