A newborn with a suspected cardiac problem is an emergency unless proved otherwise.
When to suspect congenital heart disease in a new born?
New born with difficulty in breathing, cyanosis, feeding difficulty, undue lethargy or undue irritability and insolable cry after feeding (suspect ALCAPA – anomalous origin of left coronary artery from pulmonary artery) are the situations in which congenital heart disease is suspected in a new born.
Physical examination
Physical examination is often difficult in a sick infant, but should include the assessment of pulse, respiration, colour, tone, activity, cry and murmurs. Occasionally a bounding pulse with heart failure and a large heart, but a normal echocardiogram (except for chamber dilatations), may be due the the vein of Galen aneurysm producing an arteriovenous shunting. Many infants may be branded as cardiomyopathy if a careful examination of femoral pulse is not performed to identify coarctation of aorta. Respiratory distress with increased effort as evidenced by a tracheal tug mandates ventilation. Pallor may be noted in heart failure and cyanosis in hypoxemia. Hypotonia with severe decrease in activity suggests a severe cardiac lesion. Please note that the absence of a murmur does not rule out severe congenital heart disease.
Role of X-ray chest
The x-ray chest is useful to know the state of the pulmonary blood flow, whether it is oligemic or plethoric. It is also useful for ruling out lung pathology and identifying the situs of the heart and the viscera. Oligemic lung field with a prominent main pulmonary artery segment would suggest tetralogy of Pulmonary artery with absent pulmonary valve. A large heart in a newborn should make us suspect Ebsteins anomaly of the tricuspid valve or a critical pulmonary stenosis with heart failure. Agenesis of the lung, collapse of the lung, eventration of the diaphragm and diaphragmatic hernia may be seen on the chest x-ray.
Hyperoxia test
Oxygen may be given with a hood or mask for 1 minutes, evaluating the blood before and after 100% oxygen. Saturation, PO2 and PCO2 are checked before and after the hyperoxia test. The test is useful in differentiating cyanotic congenital heart disease from lung disease.
Concerns against a hyperoxia test:
There is some concern over the induction of an irreversible ductal spasm in a ductus dependent new born, though it is extremely uncommon. Ductal spasm can also occur even without oxygen administration. Ideally PGE1 should be available to tackle duct spasm.
Pulse oximetry in the new born
Pulsoximetry should be done in all four limbs as desaturation may be there only in the lower limbs in certain situations. Obtaining a good pulsoximetry may not be easy in a sick infant. The limbs should be warm to avoid errors. The visual and auditory signals associated with pulsoximetry should be good. A good plethysmograph ensures accuracy of the technique.
Role of ECG
Arrhythmias causing tachycardiomyopathy may be occasionally identified in a new born with heart failure. New born hearts are extremely prone for heart failure with prolonged tachyarrhythmias. Big Q waves in lateral leads could suggest ALCAPA.
Role of echocardiography
Echocardiography is the most important diagnostic tool in a new born with suspected congenital heart disease. A systematic and segmental approach is essential to avoid missing important lesions. The coronaries should be specifically looked for. Optimum machine which is dedicated to echocardiography with a good neonatal probe is ideal. There is no need to emphasise the need for trained personnel. If a coarctation is not seen from the suprasternal or parasternal views, an epigastric view might demonstrate a coarctation of the abominal aorta. Other lesions which can be easily missed are infra diaphragmatic TAPVC (total anomalous pulmonary venous connection) and coarctation in the presence of a PDA (patent ductus arteriosus). Repeat echoes and second opinions are needed in difficult cases.
Role of computerised tomography (CT)
CT is useful in the differentiation of coarctation of aorta from aortic arch interruptions. Pulmonary venous drainage in heterotaxy may also be better seen on CT.
Cardiac emergencies in the newborn
They may present with severe hypoxia, severe heart failure or cardiovascular collapse. This could be because the anatomical lesions are critical or because of associated complications like pneumonia, gastroenteritis or anemia. These infants are very sick and need rapid triage and management.
Treatment of emergencies in infants with trans catheter techniques
Treatment of emergencies require a good team work of experts, good imaging and a large inventory of hardware with preferably no constraints of cath lab time or money. The expert team is composed of intensivists, anaesthetists, nurses, technicians, cardiac surgeons and the interventional cardiologists. New born emergencies are very sick with associated hypoxia, acidosis, dehydration, hypoglycemia and electrolyte imbalance. They have poor ventricular function and a low safety margin. Failed procedure in this situation would mean a higher mortality than not attempting the procedure at all.
The protocol is to stabilise initially in a new born intensive care unit (NICU) and then optimally time the intervention – not too early or too late. Attention has to be made to baseline parameters, airway and ventilation, intravenous access, blood investigations, hydration, correction of anemia, acidosis and electrolyte imbalance. Echocardiography and screening for clotting abnormalities are needed.
Once the vascular access for intervention is obtained, it is almost like half the work done. Care with contrast injection is needed to avoid cardiac and renal dysfunction in the sick neonate.
Interventional procedures in the newborn
Dilatation of valves – balloon aortic valvuloplasty (BPV), balloon pulmonary valvuloplasty
Perforation of valves – pulmonary valve in pulmonary atresia
Dilatation of vessels – coarctation of aorta
Maintaining ductal patency – stenting of the duct
Closure of PDA with coil or device
Balloon atrial septostomy
Embolisation of accessory channels as vein of Galen aneurysm or in Scimitar syndrome
Balloon atrial septostomy may even be done in the neonatal ICU in very sick infants under echo guidance. Fetal diagnosis may enable tackling of the lesion on day 1 itslef. Neonatal BPV can be done with coronary guide wires and balloons. Perforation of the atretic valve in pulmonary atresia may be done with the hard end of a guide wire. The perforation is crossed with a coronary wire and serially dilated with coronary balloons. Sometimes the perforation is also stented, though it will produce significant pulmonary regurgitation. Critical aortic stenosis can also be dilated similarly. Severe coarctation can also be dilated, though it may be a palliative procedure as a bridge to surgery. Dilatation with or without stenting for an occluded Blalock Taussig shunt is another trans catheter procedure. Recurrence is likely and needs a more definitive treatment.
Hybrid procedures in the new born
Hybrid procedures can be done either in the operating room or in hybrid suites. In closing a muscular VSD in a sick neonate not suitable for cardiopulmonary bypass, after sternotomy, the right ventricle is punctured and a guide wire is passed across the VSD. The sheath is then threaded over it followed by device delivery.