Cardiac Abnormalities in Birth Asphyxia M.S. Ranjit

Sri Ramachandra Medical College and Research Institute, Porur, Chennai, Tamil Nadu Abstract, Cardiac abnormalities in birth asphyxia were first recognised in the 1970s. These include (i) transient trLcuspid 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 newborn (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 ventficular 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 newborn (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 tension 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. [Indian J Pediatr 2000; 67 (7) : 529-532] Key words : Transient tncuspid regurgitation; Persistent pulmonary hypertension of the newbom.

Cardiac abnormalities in birth asphyxia were really recognised as an entity when Richard Rowe & his colleagues described ischaemic changes in their landmark papers in the 1970s I. Broadly these abnormalities can be classified as: 1. Transient myocardial ischaemia of the newborn (TMI of NB) 2. Transient mitral regurgitation in the newborn (MR) 3. Transient tricuspid regurgitation in the newborn (TR) 4. Persistent pulmonary hypertension of the newborn (PPHN) The second and third conditions are essentially extensions of the other two. There is considerable overlapping between these findings with some babies having all these features. Reprint requests : M.S. Ranjit, Consultant Pediatric Cardiologist, Sri Ramachandra Medical College & Research Institute, Porur, Chennai-600 116 Indian Journal of Pediatrics, 2000; 67 (7)

Transient Triscupid Regurgitation in the Newborn Tricuspid regurgitation in the newborn has been described as the commonest cause Of a cardiac murmur in the newborn in the first four days of life. In most of them this is due to PPHN and is commonly due to ischaemic damage of the tricuspid valve papillary muscles. This has been recognised in several postmortem studies. In most instances, TR is associated with PPHN and in an asphyxiated baby both are probably due to asphyxial damage. In most instances, the TR disappears in days and seldom causes any long term problems. Its importance lies in recognizing it as a marker for both PPHN and myocardial ischaemic damage due to asphyxia and realising that such a baby who is not doing well will benefit from inotropic support, ventilation and oxygen. It is easily recognised as a soft pansystolic murmur at the 529

M.S. Ranjit lower sternal edge. Isolated T R needs no therapy, unless associated with TMI of NB or PPHN.

Transient Mitral Regurgitation in the Newborn Mitral regurgitation in the newborn is far less common thanTR. However, it is an important marker of subclinical and clinicalTMI of NB. It is recognised as a soft pansystolic murmur at the apex, often heard at the base of the heart as well. Its presence in a baby with poor pulse and one who is not doing well, especially when a history of asphyxia is forthcoming, is a sure marker of TMI of NB, often with depressed left ventricular (LV) contractility. Occasionally, the LV function is normal at echocardiography (Echo). This is a more benign condition due to papillary muscle ischaemia and resolves in due course in most instances. Sometimes, however, MR can persist for weeks. Isolated MR does not need any therapy unless associated with clinical or Echo evidence of TMI of NB or of PPHN. Follow up Echo is desirable as MR can rarely persist. In fact, most of these patients have mitral valve prolapse due to mitral papillary muscle dysfunction and, on occasion, chordal rupture. This is easily recognised clinically by the pansystolic murmur at the apex. MR requires therapy more often than TR as it is commonly associated with TMI of NB and LV dysfunction. Inotropic support in a baby with poor pulse and often with features of congestive failure or radiographic evidence of pulmonary venous congestion, will be of great benefit. The sick babies need ventilation. The more severely affected do poorly.

Transient Myocardial Ischaemia of the Newborn (TMI of NB) TMI of NB was recognised by Rowe and associates 2 from the hospital for six children, Toronto, Canada. The subject remained controversial for a while before gaining widespread acceptance. Rowe recognised several types of TMI and classified them as :Type A : Respiratory distress with congestive cardiac failure Here the infant is typically a male over 3 kg in weight, APGAR scores of < 6 and history of complicated delivery as well as hypoxic stress before or after delivery. "[he liqor is often meconium stained. + Respiratory distress starts shortly after birth with variable cyanosis that does not dominate the clinical picture 3. Cardiomegaly, hepatomegaly and tachycardia or a gallop develop. There is usually a nonspecific ejection systolic murmur. Half of these babies develop a mitral regurgitant murmur. X-ray shows cardiomegaly and "wet 530

lungs". ECG shows typical changes with flattening of T waves, ST segment changes or even pathologic Q waves. Echo in these babies shows depressed left ventricular function and mitral regurgitation. Type B : Respiratory distress, congestive cardiac failure and vascular collapse The situation resembles Type A except that the baby progresses to shock or near shock in 36 hours. The pulses are weak or absent in severe cases. This is often a pointer. Echo rules out the main differential diagnoses of left heart obstructive lesions like critical aortic stenosis and hypoplastic left heart syndrome. It also reveals poor left ventricular function as well as MR. This group has a high mortality. Type C: Respiratory distress without congestive cardiacfailure. These babies have short-lived respiratory distress and mild cyanosis. It is classifiable as transient tachypnoea of the newborn. ECG shows changes and echocardiography often reveals evidence of TMI of NB. These babies usually recover.

Type D :Apparently normal babies with transient mitral regurgitation. Here the diagnosis is often picked up during evaluation of the murmur. Echo reveals the mitral regurgitation and an ECG shows typical changes. Type E: Respiratory distress in a baby with CHD Here a baby in whom symptoms are unexpected in the neonatal period i.e. a ventricular septal defect or tetralogy of Fallot, develops respiratory distress. T M I of NB should be suspected in an asphyxiated baby with respiratory distress or poor pulses or in a baby in whom a murmur is audible. Martin-Ancel et aP found that 29% of asphyxiated babies had cardiac abnormalities. CNS injury (72%), and renal injury (42%) were more frequent. Screening with an ECG and Echo is recommended. ECG is the key to the diagnosis of TMI in the NB. ECG features were described by Rowe and colleagues and this still holds good. They described the ECG changes as thltows. Grade 1 : Fxluivocal- Flat or inverted T wave in one lead only Grade 2 : Suggestive - Flat or inverted Tin several leads with abnormal Q wave in any lead. Grade 3 : Moderate - Flat or inverted T in several leads or Bundle branch block with abnormal Q plus abnormal S T segments. Indian Journal of Pediatrics, 2000; 67 (7)

Cardiac Abnormalities in Birth Asphyxia Grade 4 : Severe- Classicalsegmental infarction pauern with abnormal Q waves and markedly elevated S T segments. Creatinine phosphokinase MB fraction (CPK MB) is a useful marker but is not specific in the newborn 5. Echo usually shows impaired left ventricular, and rarely, right ventricular contractility and also associated mitral and tricuspid regurgitation. Occasionally, Echo may reveal ventticular wall motion abnormalities and even dyskinetic segments of the left ventricle. Ejection fraction of the LV is a good marker of prognosis, severity, and when done serially, of improvement or deterioration of the baby's condition. In addition, the LV or the RV often appears dilated. In the early years, TMI of NB was diagnosed using thallium 201 myocardial scans for myocardial perfusion6. This has been replaced by echocardiographic estimation of ventricular contractility and mitral or tricuspid regurgitation. Myocardial enzyme studies are of help as supporting evidence only, as raised CPK-MB fraction is nonspecific in the neonate. TMI of newborn is treated as myocardial failure with fluid restriction, inotropic support with dopamine, dobutamine or even adrenaline if required, ventilatory assistance, and diuretics. Digoxin is often a cause ofarrhythmias in such newborns and is best avoided. Afterload reduction with s o d i u m nitroprusside, nitroglycerine or captopril is seldom required except in the severe cases. TMI of NB is very often associated with PPHN. In these patients ventilatory assistance is almost always required with i n o t r o p i c s u p p o r t . Serial echocardiographic evaluation helps in assessing the severity of the disease as well as evaluating response to therapy and recovery. In patients with severe LV and often right ventricular dysfunction, long term follow up and serial Echo help the management. Most often, review Echo shows normal ventricular contractility with no mitral or tricuspid regurgitation. Seldom does MR or T R persist 7. It has been hypothesised that some cases of mitral valve prolapse are due to TMI of NB. StiU's murmur, an innocent systolic murmur often heard in the young child, is also suspected to be due to persistent T R as a sequelae of TMI of NB. The prevalence of T M l of the NB is often underestimated. In an autopsy study of asphyxiated babies, Donnelly et aP found ischaemic necrosis of the papillary muscles in 31 of 82 neonates (RV involvement in 11, LV in 13 and bilateral in 7). Martin Ansell et al4 assessing organ damage in asphyxiated neonates found CNS damage in 82% and cardiac damage in 29%. Some Others have Indian Journal of Pedlutrics, 2000; 67 (7)

found higher incidence of cardiac involvement in birth asphyxia. Flores Nava etaP found TMI of NB in 51% of 76 asphyxiated babies with a 33% mortality, qkventy percent developed cardiac failure. Respiratory distress was the principal diagnosis in 38% while neurologic problems were present in 50%. CPK-MB was raised in most of the patients. Farru et aP~ in a smaller study of 30 asphyxiated babies found TMI of NB on ECG in 25. There were 5 deaths and all of these showed subendocardial infarcts on autopsy.

Persistent Pulmonary Hypertension of the Newborn (PPHN) P P H N is defined as a c o n d i t i o n in which the hemodynamics of fetal life is maintained after birth. The pulmonary vascular bed remains constricted and there is right to left shunting across the fetal channels i.e. the ductus arteriosus and foramen ovale. Perinatal hypoxia is the commonest cause. In hypoxia the intra-acinar pulmonary arterioles are thicker with more muscle and this muscle extends more peripherally than in normal. This causes abnormal pulmonary vasoconstriction postnatall)~ During recovery the pulmonary artery pressure which is raised initially, drops gradually as the pulmonary vasoconstriction decreases. PPHN is a very common cause of neonatal respiratory distress and cyanosis. It is a very frequent cause of admission to the neonatal unit and is often under diagnosed. P P H N is well known as a result of diaphragmatic hernia and other structural and infective causes of p u l m o n a r y problems. Polycythemia is a contributing factor. Occasionally, PPHN appears without any cause and is attributed to perinatal hypoxia and often due to structural problems in the lungs and the pulmonary vasculature. Mild to moderate hypoplasia of the lungs, especially its vasculature, is a well known cause, but is difficult to prove clinically or with investigations. Several studies have shown PPHN to be due to structural problems of the pulmonary vasculature and these cases do poorly, even with extracorporeal m e m b r a n e oxygenation (ECMO). A typical patient with PPHN is a term baby with birth asphyxia or perinatal hypoxia often requiring resuscitation at birth with low APGAR scores, who presents in the first 24 hours with respiratory distress and cyanosis, often of the lower extremities.The differential cyanosis is very often difficult to recognise. Pulse oximetry may help in recognising lower saturation in the lower extremities from 531

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right to left ductal shunt. Most often, due to the atrial shunt that is almost always present, the differential cyanosis is difficult to recognise. Palpation reveals an active pericardium with mostly right ventricular or parasternal or epigastric impulse and pulmonary artery pulsations in the second space. Auscultation reveals a loud pulmonary component of the second heart sound and murmurs of TR or MR or both. PPHN should be suspected in any asphyxiated baby with respiratory distress. Diagnosis is easy if echocardiography is done. Clinical diagnosis is possible but Echo remains the key to diagnosis. Echocardiography reveals a dilated right heart and pulmonary artery, with the atrial and ventricular septae bulging into the left atrium and ventricle respectively. This finding usually demonstrates severe P P H N with suprasystemic pulmonary artery pressures. Ventricular dysfunction often coexists when birth asphyxia is the cause. Doppler and colour Doppler show right to left atrial and ductal shunting. Patency of the ductus is common in these babies and in the severest of cases the duct shunt is purely from right to left. In most cases the shunt is bidirectional with systolic right to left and diastolic left to right shunt. In milder cases ductal shunt is left to right. Ductal Doppler enables estimation of the pulmonary artery pressures. TR is almost universal in PPHN especially when severe. When Doppler is not available, systolic time intervals can also predict pulmonary artery pressures reasonably accurately. Therapy for PPHN is controversial.The mildest cases require nothing other than oxygen and general care. Severe cases require ver~tilation and often inotropic support. ECMO is an alternative in the very sick. Nitric oxide has, however, replaced ECMO in most cases **. Many units use bicarbonate therapy with inotropic and general support with good effect. Supportive care with attention to metabolic parameters is crucial. Mortality is significant in the severe cases. The diagnosis of cardiac abnormalities in the asphyxiated neonate requires a high index of suspicion and screening of suspected babies with echocardiography and ECG.The incidence is much higher than is commonly recognised. Early recognition enables better management

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Indian Journal of Pediatrics, 2000; 67 (7)