Total Anomalous Pulmonary Venous Drainage – what it is, its effects, and treatment
Four pulmonary veins should connect the lungs to the left atrium (the collecting chamber on the left side of the heart). The pulmonary veins allow oxygenated blood to flow into the left side of the heart, from where it is distributed around the body.
In total anomalous pulmonary venous drainage (TAPVD), the pulmonary veins do not join the lungs to the left atrium. Instead, they follow one or (more likely) several anomalous pathways, and connect to the circulation supplying the right side of the heart. This means that instead of the left side of the heart receiving a supply of oxygenated blood, the right side of the heart has to process this in addition to its normal supply of de-oxygenated blood.
In TAPVD, at least one hole in the septal wall (the wall dividing the right and left sides of the heart) will be present. Normally the hole will be between the atria (the collecting chambers), although that is not necessarily the case. The hole(s) is helpful in that it allows a mixture of oxygenated and de-oxygenated blood to enter the left side of the heart, which would otherwise receive no supply at all. The hole(s) also reduces the pressure of blood flowing into the lungs, which will in effect be receiving close to a double load of blood to process.
Whilst some blood passes into the left side of the heart, in the setting of TAPVD, the body receives a blood supply that is inadequately oxygenated and quantitatively insufficient.
Symptoms and effects of TAPVD
Children with TAPVD will become symptomatic at or very shortly (within the first week of life) after birth. Symptoms typically include:
- cyanosis (blueness),usually most pronounced around the lips and fingertips
if the abnormal veins are blocked, then the child will likely collapse.
- can be a greyish appearance to the skin and/or sweating and/or wheezing or grunting.
When measured, oxygen saturation levels are likely to be significantly lower than usual. However, venous oxygen levels can be far higher than normal.
There are also likely to be problems with feeding.
In unobstructed TAPVD, a more insidious decline might be expected, with the child suffering repeated chest infections and failure to thrive. If the venous supply is obstructed then it is likely that the child will be acutely unwell more or less from birth, manifesting shortness of breath, rapid heart rate and cyanosis. The majority of diagnoses are made in the first of life.
Diagnosing and treating TAPVD
As above, diagnosis is usually made soon after birth, and is confirmed by diagnostic imaging. Echocardiography (a form of ultrasound) will usually confirm the diagnosis. It is extremely helpful in the context of TAPVD, as the problem is associated with blood flow and liquid flow shows up quite clearly on ultrasound. The time of diagnosis will usually depend upon how quickly symptoms appear and what these are.
It may be necessary to clarify the structures further by additional imaging studies, possibly including MRI.
Once the diagnosis has been made and clarified, corrective surgical treatment will be required.
Surgery is conducted on cardiopulmonary bypass. A median sternotomy (a large cut down the centreline of the chest and through the breastbone) is made. The ribs are spread. The pulmonary veins are reconnected to the left atrium, and the sites at which they joined the supply to the right heart (the inferior and/or superior vena cavae) will be surgically closed. The atrial septal defect(s) and any ventricular septal defect(s) are closed.
As with any cardiac procedure which involves either time spent on cardiopulmonary bypass and either aortic cross-clamps or possibly total circulatory arrest, there is a limited amount of time within which to effect the repair, as the likelihood of damage to the heart and other organs in the body mounts with the passage of time.
TAPVD was historically associated with a relatively high mortality rate but improvements in care mean the situation is now much improved.