Cardiac abnormalities in birth
asphyxia were first recognised in 1970s. These include (i) transient
tricuspid regurgitation which is the commonest cause of a
systolic murmur in a newborn and tends to disappear without any treatment unless it is associated with transient
myocardial ischemia or
primary pulmonary hypertension of the new born (ii) transient
mitral regurgitation which is much less common and is often a part of transient
myocardial ischemia, at times with reduced left ventricular function and therefore, requires treatment in the form of inotropic and ventilatory support, (iii) transient
myocardial ischemia (TMI) of the newborn. This should be suspected in any baby with
asphyxia, respiratory distress and poor pulses especially if a murmur is audible. It is of five types (A to E) according to Rowe's classification. Type B is the most severe with respiratory distress,
congestive heart failure and
shock. Echocardiography helps to rule out critical left ventricular obstructive lesions like
hypoplastic left heart syndrome or critical
aortic stenosis. ECG is very important for diagnosis of TMI, and may show changes ranging from T wave inversion in one lead to a classical segmental
infarction pattern with abnormal q waves. CPK-MB may rise and echocardiogram shows impaired left ventricular function, mitral and/or
tricuspid regurgitation, and at times, wall motion abnormalities of left ventricle. Ejection fraction is often depressed and is a useful marker of severity and prognosis. Treatment includes fluid restriction, inotropic support,
diuretics and ventilatory resistance if required, (v) persistent
pulmonary hypertension of the new born (PPHN). Persistent
hypoxia sometimes results in persistence of constricted fetal pulmonary vascular bed causing
pulmonary arterial hypertension with consequent right to left shunt across
patent ductus arteriosus and foramen ovale. This causes respiratory distress and
cyanosis (sometimes differential). Clinical examination also reveals evidence of
pulmonary arterial hypertension and right ventricular failure with
systolic murmur of tricuspid and, at times,
mitral regurgitation. Treatment consists of
oxygen and general care for mild cases, ventilatory support, ECMO and
nitric oxide for severe cases. Cardiac abnormalities in asphyxiated neonates are often underdiagnosed and require a high index of suspicion. ECG and Echo help in early recognition and hence better management of these cases.