Dr John Lawrenson
Head: Paediatric Cardiology, Red Cross War Memorial Children’s Hospital
The surgical treatment of congenital heart disease represents one of the medical triumphs of the 20th century. In the second decade of this century, high quality survival into adulthood after surgery is the rule. In most patients, surgical correction of the defects is possible. A proportion of these patients will still not be free of the need for long-term medical follow-up, given the consequences of scar formation in the myocardium (predisposing to arrhythmias) and the use of prosthetic materials that need to be replaced (such as conduits between the right ventricle and pulmonary arteries which calcify with time).
In a relatively small number of patients, anatomical correction will not be possible. In the patient born a ‘functional single ventricle’, that ventricle will destined to support the systemic circulation. The systemic venous return will be connected to the pulmonary circulation directly (usually in two separate operations – one in the first year of life and the second in late childhood). The basic principles of therapy have been established since the late 1970s.
These ‘non-curative’ operations together with other interventions such as systemic to pulmonary shunts are known as ‘palliative’ cardiac procedures.
While these single ventricle procedures are designed to alleviate hypoxaemia and cardiac failure and therefore improve quality of life, the surgery will result in increased survival of the patient. For example, children born with only the left ventricle present (a condition known as tricuspid atresia) are likely to die in early life without surgery; after a total cavopulmonary connection (the operation referred earlier) survival into the fourth decade is the norm.
The use of the term ‘palliative’ in congenital heart disease surgery is thus slightly different to its use in untreatable malignancy. Relief of symptoms without cure is central to the treatment in both groups – palliative cardiac surgery is associated with the potential to flatten the trajectory of dying. (Many medical practitioners and patients are unfamiliar with the term ‘palliative cardiac surgery’ – the association of ‘palliative care’ with ‘short –term survival’ is the general understanding; many parents express relief that the surgery is not just to relieve pain!) .
This dramatic improvement in survival does however come at the cost of an abnormal physiological state. To establish a pulmonary circulation, the systemic venous pressure must be abnormally high. The elevated pressure will result in long term hepatic dysfunction. The single ventricle is abnormal and is likely to fail early in adulthood. Many patients with single ventricles nowadays will develop cardiac failure in the fourth decade. For a few of these patients, cardiac transplantation may be appropriate. For the remainder, mortality occurs at the time of life when peers are establishing careers.
For women with palliated single ventricle circulations, pregnancy and child birth is generally possible; death of the mother when the child is still young may be an unfortunate reality
It is hoped that improvements in surgical techniques (which include both appropriate timing of surgical steps and modifications of the new cardiac circuit) as well as the development of miniaturized implantable pumps will allow for increased survival of this challenging group of patients.