Congenital heart defects in low birth weight babies and its correlation to the health burden on the country

Dr Dhananjay Malankar, Consultant, Paediatric Cardiothoracic Surgery, Fortis Hospital, Mulund elucidates on how surgery leads to extremely good results compared to unoperated babies with TGA, where 45 per cent die within one month and 90 per cent die by end of one year

After delivery, a full term baby weighing 2.1kg was noticed to have blue lips, fingers and toes and was immediately referred to a neonatologist. An echocardiogram showed that the baby had a major heart defect called transposition of great arteries (TGA). A life saving intravenous medicine was started and the baby was urgently brought to the Paediatric Cardiac Intensive Care Unit at Fortis Hospital, Mulund, where he was stabilised on a ventilator to maintain acceptable blood oxygen level. An urgent open heart surgery ‘arterial switch’ was required to correct the heart defect and to get the baby out of the ventilator.

Low birth weight is extremely common in Indian newborns, the most important factor responsible is poor maternal nutrition. 1 in 100 babies will have some kind of heart defect, varying from a simple hole in the heart known as a septal defect to more complex defects like transposition of great arteries (TGA), truncus arteriosus, total anomalous pulmonary venous connection (TAPVC), etc. In this case, we were faced with a double dilemma of performing a major open heart surgery and that too in a low body weight precious baby!

Transposition of the great arteries (TGA) forms 5-7 per cent of all congenital heart defects; overall incidence of TGA is 0.2 cases per 1000 live births. In TGA the great vessels (aorta and pulmonary artery) are inverted, meaning the aorta which is normally connected to left side of the heart and carries pure blood to the body, is connected to the right side of the heart in TGA and carries impure blood to the body. Whereas the pulmonary artery which is normally connected to the right side of the heart and carries blue blood to the lungs, is connected to the left side of the heart in TGA and carries pure blood back to the lungs. Thus the baby was blue, as impure blood was flowing through the entire body.

Arterial switch operation is a type of open heart surgery in which the baby’s chest is opened and a heart-lung machine is used to supply blood to the body organs; and the great arteries are switched i.e. the aorta is divided and connected to the left side of the heart, and the pulmonary artery is divided and connected to the right side of the heart. Thus pure blood flows though the body relieving the baby of his bluish discolouration and enabling us to take him off the ventilator. However, the most crucial step in the surgery is the transfer of coronaries as buttons from the previous aorta to the new aorta so as to provide pure blood supply to the heart muscle. Any small error in this step can lead to failure of the entire operation as stretching or kinking of the coronaries can lead to stoppage of blood flow to the heart muscle which becomes ischaemic and suffers infarction, similar to heart attack in the adults, leading to loss of the baby’s life.

The baby underwent the arterial switch operation on day three of his life. The surgical procedure was uneventful, the baby was separated from the heart-lung machine support at the end of the operation, the chest was closed and the baby was shifted to the ICU. The baby tolerated the switch operation very well and was taken off ventilator support on post-operative day-three and gradually cardiac medications were tapered and stopped. Feeding was started six hours after surgery through nasogastric tube and after extubation, feeding amount was advanced gradually to meet the baby’s requirement. Over the period of three-four days oxygen was tapered and on post-operative day-10 the baby was discharged home with satisfactory pre-discharge echocardiogram findings. Taking care of these tiny babies post-open heart surgery is a very daunting task and needs round the clock nursing care and vigilant and caring intensivists and nurses. All aspects of the post-op care like weaning the baby from the ventilator, prevention of infection, initiation of feeds, prevention of aspiration and weaning the baby off cardiac medications are of paramount importance. Any small change in the baby’s parameter can have long –lasting and gruesome consequences and can lead to failure of all the efforts. The intensive care team played a crucial role in the smooth recovery of the baby from the surgery as evidenced by the baby being discharged on post-operative day 10.

Low body weight is considered as an important high risk factor for death after open heart surgery, the reason being highly complex nature of the surgery as the cardiac structures are too small, and the reduced tolerance of the baby to the heart-lung machine, which has its own set of complications. It is very well said that ‘Children are NOT small adults’, meaning that just miniaturisation of devices, medicines and techniques is not sufficient to treat complex defects in children. It is an entirely different patient subset, requiring personnel who are specially trained in taking care of children. Very young and low weight babies, especially premature birth babies, have immature organ systems with deficiency of blood-brain barrier, making them highly susceptible to the deleterious effects of the heart-lung machine. Also, their immune systems are immature, making them susceptible for infections in the post-operative period. During surgery there is very narrow margin for error, as smallest of mistakes get amplified and can have long lasting consequences, sometimes even amounting to loss of life. But the results are equally rewarding. Once these babies are discharged they undergo rapid growth and catch –up with their peers and even on the first follow-up visit at one month are virtually unidentifiable, which is very gratifying.

There are a few studies in literature which highlight the effect of low body weight on the results after arterial switch operation (ASO). In one study, weight less than 2.5kg was associated with mortality rate of 20 per cent after ASO, whereas weight more than 2.5kg had a mortality rate of 2 per cent. Similarly, babies weighing less than 2kg were associated with even higher mortality rate of almost 50 per cent after undergoing ASO. In high volume centres, the operative mortality of ASO approaches around 3 per cent with 10 years survival rate of 88-97 per cent and freedom from re-operation of 88 per cent! Very few children need re-operation in the future. These are extremely good results compared to the unoperated babies with TGA, where 45 per cent die within one month and 90 per cent die by the end of one year.

Reference: https://bit.ly/2wVWNbz, https://bit.ly/2wVWNbz