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Best practice critical cardiac care in the neonatal unit
EHD-04334; No of Pages 7 Early Human Development xxx (2016) xxx–xxx
Contents lists available at ScienceDirect
Early Human Development journal homepage: www.elsevier.com/locate/earlhumdev
Best practice critical cardiac care in the neonatal unit Michael L. Rigby Division of Paediatrics, Royal Brompton Hospital, London SW3 6NP, United Kingdom
a r t i c l e
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Available online xxxx Keywords: Central cyanosis Hypoxia Circulatory failure Neonatal myocardial ischaemia Myocarditis Cardiac tamponade Duct dependent pulmonary flow Duct dependent systemic flow
a b s t r a c t Major congenital or acquired heart disease in neonates presents with cyanosis, hypoxia, acute circulatory failure or cardiogenic shock. Antenatal diagnosis is made in up to 50% but heart disease is unanticipated in the remainder. The presence of significant heart disease in premature infants is also frequently not suspected at first; in general, whatever the underling cardiac anomaly, the clinical condition is worse, deteriorates more quickly and carries a poorer prognosis in premature and low birth weight infants. Although congenital cardiac malformations are the most likely, other important cardiac disorders are encountered. In general initial treatment options, often without a precise diagnosis, include diuretics, prostin, catecholamines, phosphodiesterase inhibitors, ventilation and occasionally ECMO but the key to successful treatment remains the correct diagnosis. Many conditions will only show significant improvement with treatment by the interventional cardiologist or cardiac surgeon. © 2016 Published by Elsevier Ireland Ltd.
Contents 1. 2.
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Management of hypoxia . . . . . . . . . . . . . . . . . . . . . . . 2.1. Complete transposition (TGA) . . . . . . . . . . . . . . . . . 2.2. Duct dependant pulmonary blood flow . . . . . . . . . . . . . 3. Acute circulatory failure: causes and treatment . . . . . . . . . . . . . 3.1. The role of negative inotropic factors . . . . . . . . . . . . . . 3.2. Duct dependent systemic blood flow . . . . . . . . . . . . . . 3.3. Acute heart failure caused by left to right shunting . . . . . . . . 3.4. Obstructed total anomalous pulmonary venous connection (TAPVC) 3.5. Ventilation . . . . . . . . . . . . . . . . . . . . . . . . . . 3.6. Cardiovascular drugs . . . . . . . . . . . . . . . . . . . . . . 3.7. Catecholamines . . . . . . . . . . . . . . . . . . . . . . . . 3.8. Inodilators and phosphodiesterase inhibitors . . . . . . . . . . . 4. Prenatal and perinatal factors causing hypoxia or circulatory failure . . . . 4.1. Persistent neonatal pulmonary hypertension . . . . . . . . . . . 4.2. Acute ‘transient’ neonatal myocardial ischaemia and infarction . . . 4.3. Myocarditis . . . . . . . . . . . . . . . . . . . . . . . . . . 4.4. Other causes of myocardial infarction or ischaemia . . . . . . . . 4.5. Hypertrophic cardiomyopathy . . . . . . . . . . . . . . . . . 4.6. Cardiac arrhythmias . . . . . . . . . . . . . . . . . . . . . . 4.7. Cardiac tamponade . . . . . . . . . . . . . . . . . . . . . . 4.8. Final comments . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
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E-mail address: [email protected].
http://dx.doi.org/10.1016/j.earlhumdev.2016.09.003 0378-3782/© 2016 Published by Elsevier Ireland Ltd.
Please cite this article as: M.L. Rigby, Best practice critical cardiac care in the neonatal unit, Early Hum Dev (2016), http://dx.doi.org/10.1016/ j.earlhumdev.2016.09.003
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M.L. Rigby / Early Human Development xxx (2016) xxx–xxx
1. Introduction
2.1. Complete transposition (TGA)
The presenting features of major congenital heart disease in the newborn are cyanosis and hypoxia or acute circulatory failure sometimes with cardiogenic shock. More generally available antenatal echocardiographic diagnosis now allows conditions to be diagnosed with remarkable accuracy in up to 50% but defacto heart disease is unanticipated in the remainder [1,2]. While increasing numbers of premature infants with major cardiac disease are surviving the first few days of life they are often too small to undergo major cardiac surgery. The presence of significant heart disease will frequently not be suspected at first and prematurity presents special problems in management. In general, whatever the underling cardiac anomaly, the clinical condition is worse, deteriorates more quickly and carries a poorer prognosis in premature and low birth weight infants. Although congenital cardiac malformations are the most likely not all cardiac disorders encountered in the neonate are congenital and as I will discuss may be a consequence of prenatal or perinatal events.
Simple TGA always causes marked systemic arterial desaturation and cyanosis [5]. An oxygen saturation of 70–75% is not unusual and this level of oxygenation, while being a warning of possible impending gloom, does not result in symptoms or acidosis. Although relatively unusual, the most alarming consequence of simple TGA (without VSD) is severe acute neonatal hypoxia, acidosis and collapse. When the diagnosis is known, emergency balloon atrial septostomy and intravenous prostin is the treatment of choice. Without a diagnosis and faced with a newborn infant with severe hypoxia, the logical immediate treatment is administration of prostin. Its effect is almost always to improve the clinical situation; by promoting ductal patency and allowing aortopulmonary mixing, oxygen saturations improve. The other benefit is an increase in pulmonary blood flow and consequently flow from the lungs to left atrium, causing an increase in left atrial pressure and as a result, an increased left to right shunt through a patent foramen ovale. These two mechanisms usually allow the arterial saturations to increase above 80%. Balloon atrial septostomy via a percutaneous femoral venous approach or via the umbilical vein is performed when the arterial oxygen saturation is persistently below 70%.
2. Management of hypoxia Central cyanosis secondary to congenital heart disease may result from a right to left shunt, from common mixing situations or from complete transposition of the great arteries. In general the presence of associated pulmonary stenosis makes the hypoxia more severe. (See Table 1.). Classical intrapulmonary shunting from focal or multiple pulmonary arteriovenous fistulas may cause profound cyanosis and hypoxia in the absence of any apparent congenital heart disease or lung pathology. Intrapulmonary shunting can also occur in parenchymal lung disease and pulmonary oedema. In cyanotic heart disease with severe hypoxia, positive pressure ventilation or just nasal oxygen delivery can increase oxygen saturations by up to 10% which can have a hugely beneficial effect. Persistent pulmonary hypertension of the newborn may cause severe hypoxia. What should be the initial management of unexpected hypoxia particularly if there is no immediate access to a cardiology assessment? It is important to remember that an arterial oxygen saturation as low as 68– 70% is extremely well tolerated by neonates. Acidosis begins to develop with lower saturations. Saturations of 80% and above are not a matter of immediate major concern and supplemental oxygen can be avoided and intubation and ventilation are not required. Initial examination, blood gases, CXR and ECG are essential and providing the x ray and gases do not indicate a pulmonary cause arrange a cardiology consult. If the oxygen saturation is persistently below 80% or falls further, start prostin at a dose of 5–20 μg/kg/min and add supplemental oxygen up to 80%. Persistent neonatal pulmonary hypertension will not be made worse by using prostin or oxygen. An improvement in saturations after starting prostin makes duct dependant pulmonary blood flow likely [3,4]. Insert umbilical venous and arterial lines to assist drug treatment and transport if required and inform the cardiology team.
Table 1 Causes of hypoxia. Common mixing Total anomalous pulmonary venous connection Univentricular heart variants Truncus arteriosus (Common arterial trunk) Common atrium Right to left shunts Ebstein malformation with ASD Tetralogy of Fallot Severe pulmonary stenosis with ASD Pulmonary atresia with intact ventricular septum
2.2. Duct dependant pulmonary blood flow There is a group of congenital cardiac anomalies associated with severe pulmonary stenosis or pulmonary atresia in which all or the majority of pulmonary blood flow depends on patency of the arterial duct (Table 2). As a consequence of spontaneous closure of the duct soon after birth, severe hypoxia, and consequent metabolic acidosis will result in early neonatal death. The administration of intravenous prostin will maintain ductal patency or cause a small duct to dilate allowing urgent palliative or even ‘corrective’ surgery to be performed within hours or days. Prostin is given at a dose of 3–20 μg/kg/min but the lowest effective dose should be used because the drug may cause complications the most important being hypotension due to a fall in systemic vascular resistance and apnoea (Table 3). For these reason prostin should not be given unnecessarily. In half the cases there will be an antenatal diagnosis and the foetal cardiologist will already have advised on whether or not intravenous prostin should be commenced at birth. Infants with mild to moderate pulmonary stenosis or other sources of pulmonary blood flow such as systemic artery to pulmonary artery collaterals will of course not require prostin. For premature infants considered too small for early surgical treatment the long term administration of low dose prostin (3–5 μg/kg/min) is relatively safe. In some instances an infant who is initially symptom free with mild to moderate central cyanosis and systemic arterial oxygen saturation N 78% will develop more profound cyanosis due to increasingly severe pulmonary stenosis so that early surgical treatment is needed. In cases of Tetralogy of Fallot or tricuspid atresia developing saturations below 80% or early cyanotic spells as well there is usually a good initial response to a B-blocking drug given regularly. This response is useful and safe in low birth weight premature infants who had initially been thought not to require prostin. Table 2 Duct dependant pulmonary blood flow. Tetralogy of Fallot with severe pulmonary stenosis or atresia Other examples of pulmonary atresia with VSD Pulmonary atresia with intact ventricular septum Critical pulmonary stenosis Complete AVSD with severe pulmonary stenosis or atresia ‘Single’ ventricle variants with severe pulmonary stenosis or atresia Tricuspid atresia Double inlet left ventricle Transposition or DORV with severe pulmonary stenosis or atresia Miscellaneous
Please cite this article as: M.L. Rigby, Best practice critical cardiac care in the neonatal unit, Early Hum Dev (2016), http://dx.doi.org/10.1016/ j.earlhumdev.2016.09.003
M.L. Rigby / Early Human Development xxx (2016) xxx–xxx Table 3 Complications of prostin. Apnoea Systemic arterial vasodilatation and hypotension Pulmonary arterial dilatation Pyrexia Jitteriness Seizures Diarrhoea Thrombocytopaenia Necrotising enterocolitis
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interruption, the Norwood operation for hypoplastic left heart or aortic atresia and balloon aortic valvuloplasty for critical aortic stenosis are just some of the options depending upon the precise diagnosis and condition of the infant. For example although aortic coarctation often occurs in isolation it may be associated with, among others, a large VSD, transposition of the great arteries, double inlet left ventricle and tricuspid atresia. Aortic interruption rarely occurs in isolation and is most frequently associated with VSD or common arterial trunk (‘truncus arteriosus’). (See Table 5.). 3.3. Acute heart failure caused by left to right shunting
3. Acute circulatory failure: causes and treatment The mechanism of acute circulatory failure is varied and complex depending on the primary aetiology [6]. It is not unusual for mild congestive heart failure to precede an acute episode. Dehydration, hypovolaemia, anaemia and sepsis may precipitate or make existing heart failure worse. In this review I will attempt to set out and categorise the many conditions potentially leading to severe heart failure. The general mechanisms include left ventricular systolic and diastolic dysfunction, an elevated left atrial pressure, raised pulmonary vascular resistance and pulmonary artery pressure and right ventricular dysfunction. Right and left heart failure occur in the majority and principles of emergency management are similar in most patient groups. 3.1. The role of negative inotropic factors The myocardium in early infancy is particularly sensitive to negative inotropic factors such as hypoxia, acidosis, hypocalcaemia, hypomagnesaemia and hypoglycaemia which may also aggravate coexisting heart disease. This effect is enhanced in prematurity. Any initial treatment should aim to reverse these factors. Hypocalcaemia or hypomagnesaemia alone are each known to cause ventricular dysfunction and heart failure; there is a rapid response to calcium or magnesium supplementation. 3.2. Duct dependent systemic blood flow Blood flow to the aorta and coronary arteries is essential to maintain cardiac, cerebral, renal, intestinal and liver function and may be jeopardised in the neonate by left heart obstructive lesions (Table 4) when the arterial duct constricts or closes resulting in poor tissue perfusion and profound acidosis with acute circulatory failure and cardiogenic shock. With an antenatal diagnosis in those infants at risk, insertion of umbilical venous and arterial cannulas is advisable; the immediate administration of prostin after birth should result in cardiogenic shock being avoided but in acute and unanticipated neonatal shock it should be assumed to be a consequence of duct closure in left sided obstructive lesions and intravenous prostin commenced immediately together appropriate inotropic support. The higher dose (20 μg/kg/min) will be required and even then occasionally there is a poor response in the setting of severe acidosis. After as effective resuscitation as possible, cardiological assessment will determine the diagnosis and the urgent treatment of choice. Surgical repair of aortic coarctation or aortic Table 4 Duct dependant systemic blood flow. Hypoplastic left heart syndrome Coarctation of the aorta Aortic interruption (usually with VSD) Critical Aortic stenosis Aortic atresia Severe mitral stenosis Miscellaneous
In the newborn, pulmonary vascular resistance (PVR) is elevated and in normal circumstances falls during the first 2 weeks of life. In the presence of conditions allowing a large left to right shunt (Table 4) there is a delayed fall in PVR and typically until 4–8 weeks of age so that severe congestive heart failure (CHF) is delayed until the second month although increasing tachypnoea is often observed during the first month. The situation is quite different in premature infants in whom PVR is lower from the outset and falls more rapidly. Thus the premature infant with a large duct and/or unanticipated congenital heart disease will develop the clinical features of severe CHF earlier. The absence of a heart murmur may delay the realisation of a cardiac cause for symptoms and characteristically the pulmonary oedema results in a fall in arterial oxygen concentration to below 90%. The administration of oxygen lowers PVR even more, aggravates the already severe CHF and leads to rapid deterioration. The key to management is of course the realisation of an underlying large left to right shunt and the avoidance of supplemental oxygen. Whatever the gestation, the initial treatment of severe CHF is diuretics and if necessary cautious use of inotropes such as dopamine or dobutamine. The return of spontaneous urine output and resolution of metabolic acidosis represents signs of therapeutic success but some patients will require intravenous furosemide. After initial resuscitation and achievement of relative stability, urgent treatment of the underlying cardiac malformation should be planned. For premature infants b1800 g continuing medical treatment is preferable to repair with cardiopulmonary by-pass. The exception is a premature infant with a large PDA and severe heart failure unresponsive to or unsuitable for a prostaglandin inhibitor. The duct can be closed safely via the femoral vein using transcatheter embolisation techniques at a weight above 1500 g; smaller infants will need surgical ligation. 3.4. Obstructed total anomalous pulmonary venous connection (TAPVC) Obstructed TAPVC is a life threatening condition presenting as severe hypoxia, acute circulatory and respiratory failure with marked CO2 retention within hours of birth. The responds to resuscitative measures and ECMO is poor it should be considered a surgical emergency requiring urgent repair. The condition masquerades as respiratory distress in hyaline membrane disease and the severe hypoxia fails to respond to prostin. In TAPVC, all the pulmonary veins drain by abnormal routes directly or indirectly to the right atrium and therefore there are a variety of morphological types. Supracardiac drainage via a vertical vein to innominate Table 5 Acute circulatory failure due to anomalies with a left to right shunt. Patent arterial duct (PDA) VSD (large) Complete Atrioventricular Septal Defect Common arterial trunk (truncus arteriosus) TGA with large VSD Aortopulmonary window Miscellaneous
Please cite this article as: M.L. Rigby, Best practice critical cardiac care in the neonatal unit, Early Hum Dev (2016), http://dx.doi.org/10.1016/ j.earlhumdev.2016.09.003
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and right superior caval veins is the most common. The pulmonary veins may drain directly to the right atrium or enter via the coronary sinus. Infracardiac drainage via a common descending vein to hepatic portal vein, ductus venosus and inferior caval vein is the least common. Survival depends on the presence of an interatrial communication permitting a right to left shunt. Whereas without obstruction, newborn infants are symptom free, obstruction to pulmonary venous return causes severe respiratory distress with marked subcostal and intercostal recession, severe hypoxia with an oxygen saturation of 70% or less, marked hepatomegaly and a very loud pulmonary component to the second heart sound because of severe pulmonary hypertension. The characteristic chest X ray changes are pulmonary venous congestion and pulmonary oedema with a miliary or reticular pattern and a small heart. Obstruction is usual in the infracardiac type, uncommon in supracardiac drainage and rare in anomalous drainage to coronary sinus. The condition is sometimes seen in cases of right atrial isomerism with complete atrioventricular septal defect, double outlet right ventricle and severe pulmonary stenosis or atresia. 3.5. Ventilation The primary function of ventilation is to maintain optimum pulmonary gas exchange. It provides an important advantage in patients with pulmonary oedema from heart failure. By increasing cardiac output, positive pressure ventilation is an important haemodynamic tool in infants with symptomatic circulatory failure associated with cardiac disease and impairment of left ventricular systolic function. Low ventilator pressures and early extubation are of benefit to patients with ventricular diastolic dysfunction of the type which might arise in left heart obstructive lesions or critical pulmonary stenosis and pulmonary atresia with intact ventricular septum. Initially however there would be no pointer to this. The use of supplemental nitric oxide and oxygen to reduce pulmonary vascular resistance in infants with cardiac disease and pulmonary hypertension must be avoided in patients suffering from circulatory failure due to an increased pulmonary blood flow. These pulmonary vasodilators merely increase the degree of pulmonary oedema and enhance the already high pulmonary blood flow.
3.8. Inodilators and phosphodiesterase inhibitors Having both inotropic and vasodilator properties these drugs are classified as ‘inodilators’. Milrinone, the one in common usage, is used for the treatment of acute circulatory failure or prevention in high risk cases with ventricular dysfunction. Laevosimendan, another inodilator, may have a superior effect on myocardial contractility in infants. Diuretics should be used if there is clear evidence of heart failure and intravenous furosemide 0.5 mg per kg stat is sufficient to begin with. Avoid dehydration at all costs. 4. Prenatal and perinatal factors causing hypoxia or circulatory failure 4.1. Persistent neonatal pulmonary hypertension The first major circulatory event at birth is an acute fall in pulmonary vascular resistance brought about by the onset of respiration and leading to an immediate increase in pulmonary blood flow. But the pulmonary vascular resistance remains elevated and the newborn infant is vulnerable to any form of hypoxic stimulus from delayed spontaneous respiration to birth asphyxia. Even a mild hypoxic stimulus can stimulate an exaggerated pulmonary vascular response with severe pulmonary vasoconstriction, leading to profound hypoxia and acidosis [8,9]. The hypoxia then becomes part of a vicious circle of worsening and life threatening vasoconstriction. There is severely reduced pulmonary blood flow and systemic flow is from right to left atrial and ductal shunting. Faced with newborn with severe cyanosis and oxygen saturation which may have fallen below 60% immediate resuscitation and administration of prostin and oxygen is needed. It will often be assumed that cyanotic heart disease is the cause. The abrupt increase in right ventricular work brought about by pulmonary vasoconstriction may cause subendocardial myocardial ischaemia and even infarction accompanied by tricuspid regurgitation. Echocardiography will exclude congenital heart disease, usually reveals a large PDA and may show not only right but also even left ventricular dysfunction. Enzyme and ECG changes of myocardial ischaemia will be discovered. Management of acute pulmonary hypertension is difficult but the principles are to ventilate, maintain oxygenation, ensure CO2 elimination, administer nitric oxide, consider intravenous prostacyclin and if necessary use inotropes.
3.6. Cardiovascular drugs
4.2. Acute ‘transient’ neonatal myocardial ischaemia and infarction
The approach to pharmacological therapy for acute circulatory failure has moved away from direct enhancement of myocardial contractility [7]. Rather than using specific inotropes, drugs with direct effects on peripheral vasculature have been employed as well. The goals are to optimise afterload while enhancing myocardial contractility with lower doses of inotropes and avoiding therefore unwanted increases in vascular resistance and myocardial oxygen consumption. Catecholamines and phosphodiesterase inhibitors are the mainstay of treatment.
This well recognised condition was first described in great detail by Richard Rowe [10,11] and there is little doubt it is under diagnosed by neonatologists and cardiologists. It typically arises as a consequence of perinatal birth asphyxia. Meconium staining of the liquor is common and the birth asphyxia is sometimes considered relatively mild. The clinical features are similar to those of myocarditis (tachypnoea and tachycardia with liver enlargement) although on echocardiography the right ventricle is more frequently involved because of subendocardial myocardial ischaemia secondary to severe persistent pulmonary hypertension. Again typical features are evidence of ischaemia or infarction on the ECG (Figs. 1–3) and cardiac enzymes are elevated. Cross-sectional echocardiography reveals significant tricuspid regurgitation and right and left ventricular dysfunction. There is often a good response to inotropic support and the prognosis is good in the majority with complete recovery and generation of new myocardium although ventricular arrhythmias and neonatal death may occur and prematurity is an additional risk factor for poor outcome.
3.7. Catecholamines Adrenaline increases heart rate and myocardial contractility but at higher does increases systemic vascular resistance although the effect is unpredictable. Noradrenaline causes systemic vasoconstriction and is useful in patients with extreme vasodilation but best avoided in patients with ventricular dysfunction. Dopamine increase myocardial contractility, heart rate and vascular tone and is useful at lower doses in infants with impaired ventricular function. Dobutamine increases myocardial contractility and heart rate and reduces systemic vascular resistance and benefits some infants in lower doses. Overall the response to catecholamines is somewhat unpredictable in part as a consequence of the multiple physiological effects. However they remain part of the first line therapy in acute circulatory failure.
4.3. Myocarditis When a mothers suffers from what is often an unremarkable viral illness during the last trimester, there is a small chance the newborn infant will have myocarditis with dilated cardiomyopathy [12]. The
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M.L. Rigby / Early Human Development xxx (2016) xxx–xxx
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Fig. 1. Normal ECG from a 4 day old infant showing usual T wave morphology.
consequence may be acute deterioration, tachycardia, tachypnoea, liver enlargement and the clinical picture of rapid onset congestive cardiac failure, low cardiac output and pulmonary oedema which might be misconstrued as acute respiratory distress syndrome. Support for the diagnosis is raised cardiac enzymes, generalised ECG T wave changes (Fig. 2), sometimes with evidence of myocardial infarction, cardiomegaly on
a chest radiograph and impaired left ventricular systolic and sometimes diastolic function on echocardiography. Intubation and ventilation and inotropic support are often required and ECMO occasionally but the prognosis is poor and aggravated by prematurity. Other forms of dilated cardiomyopathy acquired in utero also rarely present in the first days of life.
Fig. 2. ECG from a 7 day infant with myocarditis and myocardial infarction with typical S-T segment elevation in leads V1-V6 and leads 1 and aVL.
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M.L. Rigby / Early Human Development xxx (2016) xxx–xxx
Fig. 3. ECG from a 3 day old infant with a history of perinatal asphyxia. There is evidence of myocardial ischaemia/infarction with S-T segment elevation and depression.
4.4. Other causes of myocardial infarction or ischaemia
4.6. Cardiac arrhythmias
Coronary artery stenosis or atresia sometimes occurs in isolation but is usually found in hearts with pulmonary atresia and intact ventricular septum. In these cases fistulas communications between the right ventricle and coronary arteries may not provide adequate coronary flow resulting in impaired ventricular function with obvious ischaemia or infarction evident on an electrocardiogram. The prognosis is poor and characterised by the early development of cardiogenic shock; cardiac transplantation is the only treatment option. Coronary embolism in cyanotic heart disease or hearts with a right to left atrial shunt is rare and results from the inadvertent injection of thrombus or air through a venous cannula. Myocardial ischaemia usually resolves with supportive treatment. Although anomalous origin of a coronary artery from the pulmonary artery is an important cause of myocardial ischaemia/infarction, in term infants, symptoms rarely develop before the age of 6 weeks. The reason for this is a delayed fall in pulmonary artery pressure and vascular resistance maintaining adequate blood flow to the anomalous coronary. Only when the pulmonary artery pressure begins to approach normal levels is coronary perfusion inadequate causing ischaemia and subsequent life threatening infarction. All the usual clinical, laboratory, ECG and echocardiographic features will be present. Expert echocardiography also allows demonstration of the anomalous coronary artery origin. Premature infants who usually have a lower pulmonary vascular resistance develop severe circulatory failure earlier.
Supraventricular or atrial tachycardia beginning in the third trimester may continue after birth causing severe left ventricular dysfunction. If initial treatment with intravenous adenosine or cardioversion fails to establish sinus rhythm, consider amiodarone as the treatment of choice and if necessary administer adenosine again after 12 h. Beta blocking drugs are contraindicated in the presence of ventricular dysfunction.
4.5. Hypertrophic cardiomyopathy Rarely some forms of hypertrophic cardiomyopathy acquired antenatally may present soon after birth with acute circulatory failure. Examples include those associated with Noonan's syndrome and Pompe's disease but other types are also described. Such an early presentation is indicative of an extremely poor outcome whatever treatment option is used.
4.7. Cardiac tamponade A pericardial effusion with cardiac tamponade is rare immediately after birth but may be a consequence of foetal heart failure or hydrops and viral pericarditis. The cardiac causes of hydrops include severe tricuspid regurgitation, critical aortic stenosis and antenatal tachyarrhythmias. Spontaneous perinatal pneumopericardium will produce a similar clinical picture of low cardiac output, tachycardia, hypotension and liver enlargement but in addition to cardiomegaly on the chest X ray, air will be evident around the heart. Echocardiography establishes the presence of a large pericardial effusion and any associated cardiac anomalies. Immediate pericardiocentesis can be life-saving and should not be delayed; if possible use ultrasound screening, insert a small gauge needle with a subxiphoid approach and aspirate the straw colours fluid or air. With a 22 gauge needle, inadvertent puncture of the heart will not cause life threatening bleeding. In addition a soft 0.018 guide wire, readily available on a neonatal unit, can be passed through the cannula when it occupies a satisfactory position in the pericardial space; a larger cannula can then be used to replace the smaller one allowing a more efficient aspiration. 4.8. Final comments Thus there are many conditions with the capacity to cause acute circulatory failure or severe hypoxia in the neonate. An awareness of the possibilities, a high index of suspicion, an ability to interpret physical
Please cite this article as: M.L. Rigby, Best practice critical cardiac care in the neonatal unit, Early Hum Dev (2016), http://dx.doi.org/10.1016/ j.earlhumdev.2016.09.003
M.L. Rigby / Early Human Development xxx (2016) xxx–xxx
finding, ECG abnormalities and the chest X-ray is an important first step to prompt diagnosis. No conflicts and no disclosures. References [1] E. Garne, C. Stoll, M. Clementi, Evaluation of prenatal diagnosis of congenital heart disease by ultrasound: experience from 20 European registries, Ultrasound Obstet. Gynecol. 17 (2001) 386–391. [2] C.L. van Velzen, S.A. Clur, M.E. Rijlaarsdam, E. Pajkrt, C.J. Bax, J. Hruda, C.J. de Groot, N.A. Blom, M.C. Haak, Prenatal diagnosis of congenital heart defects: accuracy and discrepancies in a multicenter cohort, Ultrasound Obstet. Gynecol. 47 (5) (2016) 616–622. [3] M.A. Heyman, A.M. Rudolph, Ductus arteriosus dilatation by prostaglandin E. in infants with pulmonary atresia, Pediatrics 59 (1977) 325–329. [4] P.M. Olley, F. Coceani, E. Bodach, E-type prostaglandins. A new emergency therapy for certain cyanotic congenital heart malformations, Circulation 53 (1976) 728–731. [5] C. Salih, C. Brizard, D.J. Penny, A. RH, Transposition, in: A. RH, B. EJ, P. DJ, R. AN, R. ML, G. Wernovsky (Eds.), Paediatric Cardiology, Churchill Livingstone, Philadelphia 2010, pp. 795–817.
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[6] Z. Slavik, G. MA, Principles of medical management, in: D. PEF, R. ML, K. Niwa (Eds.), Paediatric Heart Disease, Wiley-Blackwell, Oxford 2012, pp. 239–245. [7] H. TM1, G. Wernovsky, A. AM, K. TJ, N. DP, C. AC, et al., Efficacy and safety of milrinone in preventing low cardiac output syndrome in infants and children after corrective surgery for congenital heart disease, Circulation 25 (107(7)) (2003) 996–1002. [8] S.G. Haworth, L. Reid, Persistent fetal circulation: newly recognised structural features, J. Paediat. 88 (1976) 614–620. [9] M. Rabinovitch, Molecular pathogenesis of pulmonary arterial hypertension, J. Clin. Invest. 118 (2008) 2372–2379. [10] R.D. Rowe, Abnormal pulmonary vasoconstriction in the newborn, Paediatrics 59 (1977) 318–320. [11] R.D. Rowe, T. Hoffmann, Transient myocardial ischaemia of the newborn infant. A form of severe cardiorespiratory distress in full term infants, J. Paediat. 81 (1972) 243–250. [12] J.P. Kaski, E. P., Cardiomyopathies, in: A. RH, B. EJ, P. DJ, R. AN, R. ML, G. Wernovsky (Eds.), Paediatric Cardiology, Churchill Livingstone, Philadelphia 2010, pp. 1003–1034.
Please cite this article as: M.L. Rigby, Best practice critical cardiac care in the neonatal unit, Early Hum Dev (2016), http://dx.doi.org/10.1016/ j.earlhumdev.2016.09.003
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Early Human Development journal homepage: www.elsevier.com/locate/earlhumdev
Best practice critical cardiac care in the neonatal unit Michael L. Rigby Division of Paediatrics, Royal Brompton Hospital, London SW3 6NP, United Kingdom
a r t i c l e
i n f o
Available online xxxx Keywords: Central cyanosis Hypoxia Circulatory failure Neonatal myocardial ischaemia Myocarditis Cardiac tamponade Duct dependent pulmonary flow Duct dependent systemic flow
a b s t r a c t Major congenital or acquired heart disease in neonates presents with cyanosis, hypoxia, acute circulatory failure or cardiogenic shock. Antenatal diagnosis is made in up to 50% but heart disease is unanticipated in the remainder. The presence of significant heart disease in premature infants is also frequently not suspected at first; in general, whatever the underling cardiac anomaly, the clinical condition is worse, deteriorates more quickly and carries a poorer prognosis in premature and low birth weight infants. Although congenital cardiac malformations are the most likely, other important cardiac disorders are encountered. In general initial treatment options, often without a precise diagnosis, include diuretics, prostin, catecholamines, phosphodiesterase inhibitors, ventilation and occasionally ECMO but the key to successful treatment remains the correct diagnosis. Many conditions will only show significant improvement with treatment by the interventional cardiologist or cardiac surgeon. © 2016 Published by Elsevier Ireland Ltd.
Contents 1. 2.
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Management of hypoxia . . . . . . . . . . . . . . . . . . . . . . . 2.1. Complete transposition (TGA) . . . . . . . . . . . . . . . . . 2.2. Duct dependant pulmonary blood flow . . . . . . . . . . . . . 3. Acute circulatory failure: causes and treatment . . . . . . . . . . . . . 3.1. The role of negative inotropic factors . . . . . . . . . . . . . . 3.2. Duct dependent systemic blood flow . . . . . . . . . . . . . . 3.3. Acute heart failure caused by left to right shunting . . . . . . . . 3.4. Obstructed total anomalous pulmonary venous connection (TAPVC) 3.5. Ventilation . . . . . . . . . . . . . . . . . . . . . . . . . . 3.6. Cardiovascular drugs . . . . . . . . . . . . . . . . . . . . . . 3.7. Catecholamines . . . . . . . . . . . . . . . . . . . . . . . . 3.8. Inodilators and phosphodiesterase inhibitors . . . . . . . . . . . 4. Prenatal and perinatal factors causing hypoxia or circulatory failure . . . . 4.1. Persistent neonatal pulmonary hypertension . . . . . . . . . . . 4.2. Acute ‘transient’ neonatal myocardial ischaemia and infarction . . . 4.3. Myocarditis . . . . . . . . . . . . . . . . . . . . . . . . . . 4.4. Other causes of myocardial infarction or ischaemia . . . . . . . . 4.5. Hypertrophic cardiomyopathy . . . . . . . . . . . . . . . . . 4.6. Cardiac arrhythmias . . . . . . . . . . . . . . . . . . . . . . 4.7. Cardiac tamponade . . . . . . . . . . . . . . . . . . . . . . 4.8. Final comments . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
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http://dx.doi.org/10.1016/j.earlhumdev.2016.09.003 0378-3782/© 2016 Published by Elsevier Ireland Ltd.
Please cite this article as: M.L. Rigby, Best practice critical cardiac care in the neonatal unit, Early Hum Dev (2016), http://dx.doi.org/10.1016/ j.earlhumdev.2016.09.003
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M.L. Rigby / Early Human Development xxx (2016) xxx–xxx
1. Introduction
2.1. Complete transposition (TGA)
The presenting features of major congenital heart disease in the newborn are cyanosis and hypoxia or acute circulatory failure sometimes with cardiogenic shock. More generally available antenatal echocardiographic diagnosis now allows conditions to be diagnosed with remarkable accuracy in up to 50% but defacto heart disease is unanticipated in the remainder [1,2]. While increasing numbers of premature infants with major cardiac disease are surviving the first few days of life they are often too small to undergo major cardiac surgery. The presence of significant heart disease will frequently not be suspected at first and prematurity presents special problems in management. In general, whatever the underling cardiac anomaly, the clinical condition is worse, deteriorates more quickly and carries a poorer prognosis in premature and low birth weight infants. Although congenital cardiac malformations are the most likely not all cardiac disorders encountered in the neonate are congenital and as I will discuss may be a consequence of prenatal or perinatal events.
Simple TGA always causes marked systemic arterial desaturation and cyanosis [5]. An oxygen saturation of 70–75% is not unusual and this level of oxygenation, while being a warning of possible impending gloom, does not result in symptoms or acidosis. Although relatively unusual, the most alarming consequence of simple TGA (without VSD) is severe acute neonatal hypoxia, acidosis and collapse. When the diagnosis is known, emergency balloon atrial septostomy and intravenous prostin is the treatment of choice. Without a diagnosis and faced with a newborn infant with severe hypoxia, the logical immediate treatment is administration of prostin. Its effect is almost always to improve the clinical situation; by promoting ductal patency and allowing aortopulmonary mixing, oxygen saturations improve. The other benefit is an increase in pulmonary blood flow and consequently flow from the lungs to left atrium, causing an increase in left atrial pressure and as a result, an increased left to right shunt through a patent foramen ovale. These two mechanisms usually allow the arterial saturations to increase above 80%. Balloon atrial septostomy via a percutaneous femoral venous approach or via the umbilical vein is performed when the arterial oxygen saturation is persistently below 70%.
2. Management of hypoxia Central cyanosis secondary to congenital heart disease may result from a right to left shunt, from common mixing situations or from complete transposition of the great arteries. In general the presence of associated pulmonary stenosis makes the hypoxia more severe. (See Table 1.). Classical intrapulmonary shunting from focal or multiple pulmonary arteriovenous fistulas may cause profound cyanosis and hypoxia in the absence of any apparent congenital heart disease or lung pathology. Intrapulmonary shunting can also occur in parenchymal lung disease and pulmonary oedema. In cyanotic heart disease with severe hypoxia, positive pressure ventilation or just nasal oxygen delivery can increase oxygen saturations by up to 10% which can have a hugely beneficial effect. Persistent pulmonary hypertension of the newborn may cause severe hypoxia. What should be the initial management of unexpected hypoxia particularly if there is no immediate access to a cardiology assessment? It is important to remember that an arterial oxygen saturation as low as 68– 70% is extremely well tolerated by neonates. Acidosis begins to develop with lower saturations. Saturations of 80% and above are not a matter of immediate major concern and supplemental oxygen can be avoided and intubation and ventilation are not required. Initial examination, blood gases, CXR and ECG are essential and providing the x ray and gases do not indicate a pulmonary cause arrange a cardiology consult. If the oxygen saturation is persistently below 80% or falls further, start prostin at a dose of 5–20 μg/kg/min and add supplemental oxygen up to 80%. Persistent neonatal pulmonary hypertension will not be made worse by using prostin or oxygen. An improvement in saturations after starting prostin makes duct dependant pulmonary blood flow likely [3,4]. Insert umbilical venous and arterial lines to assist drug treatment and transport if required and inform the cardiology team.
Table 1 Causes of hypoxia. Common mixing Total anomalous pulmonary venous connection Univentricular heart variants Truncus arteriosus (Common arterial trunk) Common atrium Right to left shunts Ebstein malformation with ASD Tetralogy of Fallot Severe pulmonary stenosis with ASD Pulmonary atresia with intact ventricular septum
2.2. Duct dependant pulmonary blood flow There is a group of congenital cardiac anomalies associated with severe pulmonary stenosis or pulmonary atresia in which all or the majority of pulmonary blood flow depends on patency of the arterial duct (Table 2). As a consequence of spontaneous closure of the duct soon after birth, severe hypoxia, and consequent metabolic acidosis will result in early neonatal death. The administration of intravenous prostin will maintain ductal patency or cause a small duct to dilate allowing urgent palliative or even ‘corrective’ surgery to be performed within hours or days. Prostin is given at a dose of 3–20 μg/kg/min but the lowest effective dose should be used because the drug may cause complications the most important being hypotension due to a fall in systemic vascular resistance and apnoea (Table 3). For these reason prostin should not be given unnecessarily. In half the cases there will be an antenatal diagnosis and the foetal cardiologist will already have advised on whether or not intravenous prostin should be commenced at birth. Infants with mild to moderate pulmonary stenosis or other sources of pulmonary blood flow such as systemic artery to pulmonary artery collaterals will of course not require prostin. For premature infants considered too small for early surgical treatment the long term administration of low dose prostin (3–5 μg/kg/min) is relatively safe. In some instances an infant who is initially symptom free with mild to moderate central cyanosis and systemic arterial oxygen saturation N 78% will develop more profound cyanosis due to increasingly severe pulmonary stenosis so that early surgical treatment is needed. In cases of Tetralogy of Fallot or tricuspid atresia developing saturations below 80% or early cyanotic spells as well there is usually a good initial response to a B-blocking drug given regularly. This response is useful and safe in low birth weight premature infants who had initially been thought not to require prostin. Table 2 Duct dependant pulmonary blood flow. Tetralogy of Fallot with severe pulmonary stenosis or atresia Other examples of pulmonary atresia with VSD Pulmonary atresia with intact ventricular septum Critical pulmonary stenosis Complete AVSD with severe pulmonary stenosis or atresia ‘Single’ ventricle variants with severe pulmonary stenosis or atresia Tricuspid atresia Double inlet left ventricle Transposition or DORV with severe pulmonary stenosis or atresia Miscellaneous
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M.L. Rigby / Early Human Development xxx (2016) xxx–xxx Table 3 Complications of prostin. Apnoea Systemic arterial vasodilatation and hypotension Pulmonary arterial dilatation Pyrexia Jitteriness Seizures Diarrhoea Thrombocytopaenia Necrotising enterocolitis
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interruption, the Norwood operation for hypoplastic left heart or aortic atresia and balloon aortic valvuloplasty for critical aortic stenosis are just some of the options depending upon the precise diagnosis and condition of the infant. For example although aortic coarctation often occurs in isolation it may be associated with, among others, a large VSD, transposition of the great arteries, double inlet left ventricle and tricuspid atresia. Aortic interruption rarely occurs in isolation and is most frequently associated with VSD or common arterial trunk (‘truncus arteriosus’). (See Table 5.). 3.3. Acute heart failure caused by left to right shunting
3. Acute circulatory failure: causes and treatment The mechanism of acute circulatory failure is varied and complex depending on the primary aetiology [6]. It is not unusual for mild congestive heart failure to precede an acute episode. Dehydration, hypovolaemia, anaemia and sepsis may precipitate or make existing heart failure worse. In this review I will attempt to set out and categorise the many conditions potentially leading to severe heart failure. The general mechanisms include left ventricular systolic and diastolic dysfunction, an elevated left atrial pressure, raised pulmonary vascular resistance and pulmonary artery pressure and right ventricular dysfunction. Right and left heart failure occur in the majority and principles of emergency management are similar in most patient groups. 3.1. The role of negative inotropic factors The myocardium in early infancy is particularly sensitive to negative inotropic factors such as hypoxia, acidosis, hypocalcaemia, hypomagnesaemia and hypoglycaemia which may also aggravate coexisting heart disease. This effect is enhanced in prematurity. Any initial treatment should aim to reverse these factors. Hypocalcaemia or hypomagnesaemia alone are each known to cause ventricular dysfunction and heart failure; there is a rapid response to calcium or magnesium supplementation. 3.2. Duct dependent systemic blood flow Blood flow to the aorta and coronary arteries is essential to maintain cardiac, cerebral, renal, intestinal and liver function and may be jeopardised in the neonate by left heart obstructive lesions (Table 4) when the arterial duct constricts or closes resulting in poor tissue perfusion and profound acidosis with acute circulatory failure and cardiogenic shock. With an antenatal diagnosis in those infants at risk, insertion of umbilical venous and arterial cannulas is advisable; the immediate administration of prostin after birth should result in cardiogenic shock being avoided but in acute and unanticipated neonatal shock it should be assumed to be a consequence of duct closure in left sided obstructive lesions and intravenous prostin commenced immediately together appropriate inotropic support. The higher dose (20 μg/kg/min) will be required and even then occasionally there is a poor response in the setting of severe acidosis. After as effective resuscitation as possible, cardiological assessment will determine the diagnosis and the urgent treatment of choice. Surgical repair of aortic coarctation or aortic Table 4 Duct dependant systemic blood flow. Hypoplastic left heart syndrome Coarctation of the aorta Aortic interruption (usually with VSD) Critical Aortic stenosis Aortic atresia Severe mitral stenosis Miscellaneous
In the newborn, pulmonary vascular resistance (PVR) is elevated and in normal circumstances falls during the first 2 weeks of life. In the presence of conditions allowing a large left to right shunt (Table 4) there is a delayed fall in PVR and typically until 4–8 weeks of age so that severe congestive heart failure (CHF) is delayed until the second month although increasing tachypnoea is often observed during the first month. The situation is quite different in premature infants in whom PVR is lower from the outset and falls more rapidly. Thus the premature infant with a large duct and/or unanticipated congenital heart disease will develop the clinical features of severe CHF earlier. The absence of a heart murmur may delay the realisation of a cardiac cause for symptoms and characteristically the pulmonary oedema results in a fall in arterial oxygen concentration to below 90%. The administration of oxygen lowers PVR even more, aggravates the already severe CHF and leads to rapid deterioration. The key to management is of course the realisation of an underlying large left to right shunt and the avoidance of supplemental oxygen. Whatever the gestation, the initial treatment of severe CHF is diuretics and if necessary cautious use of inotropes such as dopamine or dobutamine. The return of spontaneous urine output and resolution of metabolic acidosis represents signs of therapeutic success but some patients will require intravenous furosemide. After initial resuscitation and achievement of relative stability, urgent treatment of the underlying cardiac malformation should be planned. For premature infants b1800 g continuing medical treatment is preferable to repair with cardiopulmonary by-pass. The exception is a premature infant with a large PDA and severe heart failure unresponsive to or unsuitable for a prostaglandin inhibitor. The duct can be closed safely via the femoral vein using transcatheter embolisation techniques at a weight above 1500 g; smaller infants will need surgical ligation. 3.4. Obstructed total anomalous pulmonary venous connection (TAPVC) Obstructed TAPVC is a life threatening condition presenting as severe hypoxia, acute circulatory and respiratory failure with marked CO2 retention within hours of birth. The responds to resuscitative measures and ECMO is poor it should be considered a surgical emergency requiring urgent repair. The condition masquerades as respiratory distress in hyaline membrane disease and the severe hypoxia fails to respond to prostin. In TAPVC, all the pulmonary veins drain by abnormal routes directly or indirectly to the right atrium and therefore there are a variety of morphological types. Supracardiac drainage via a vertical vein to innominate Table 5 Acute circulatory failure due to anomalies with a left to right shunt. Patent arterial duct (PDA) VSD (large) Complete Atrioventricular Septal Defect Common arterial trunk (truncus arteriosus) TGA with large VSD Aortopulmonary window Miscellaneous
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and right superior caval veins is the most common. The pulmonary veins may drain directly to the right atrium or enter via the coronary sinus. Infracardiac drainage via a common descending vein to hepatic portal vein, ductus venosus and inferior caval vein is the least common. Survival depends on the presence of an interatrial communication permitting a right to left shunt. Whereas without obstruction, newborn infants are symptom free, obstruction to pulmonary venous return causes severe respiratory distress with marked subcostal and intercostal recession, severe hypoxia with an oxygen saturation of 70% or less, marked hepatomegaly and a very loud pulmonary component to the second heart sound because of severe pulmonary hypertension. The characteristic chest X ray changes are pulmonary venous congestion and pulmonary oedema with a miliary or reticular pattern and a small heart. Obstruction is usual in the infracardiac type, uncommon in supracardiac drainage and rare in anomalous drainage to coronary sinus. The condition is sometimes seen in cases of right atrial isomerism with complete atrioventricular septal defect, double outlet right ventricle and severe pulmonary stenosis or atresia. 3.5. Ventilation The primary function of ventilation is to maintain optimum pulmonary gas exchange. It provides an important advantage in patients with pulmonary oedema from heart failure. By increasing cardiac output, positive pressure ventilation is an important haemodynamic tool in infants with symptomatic circulatory failure associated with cardiac disease and impairment of left ventricular systolic function. Low ventilator pressures and early extubation are of benefit to patients with ventricular diastolic dysfunction of the type which might arise in left heart obstructive lesions or critical pulmonary stenosis and pulmonary atresia with intact ventricular septum. Initially however there would be no pointer to this. The use of supplemental nitric oxide and oxygen to reduce pulmonary vascular resistance in infants with cardiac disease and pulmonary hypertension must be avoided in patients suffering from circulatory failure due to an increased pulmonary blood flow. These pulmonary vasodilators merely increase the degree of pulmonary oedema and enhance the already high pulmonary blood flow.
3.8. Inodilators and phosphodiesterase inhibitors Having both inotropic and vasodilator properties these drugs are classified as ‘inodilators’. Milrinone, the one in common usage, is used for the treatment of acute circulatory failure or prevention in high risk cases with ventricular dysfunction. Laevosimendan, another inodilator, may have a superior effect on myocardial contractility in infants. Diuretics should be used if there is clear evidence of heart failure and intravenous furosemide 0.5 mg per kg stat is sufficient to begin with. Avoid dehydration at all costs. 4. Prenatal and perinatal factors causing hypoxia or circulatory failure 4.1. Persistent neonatal pulmonary hypertension The first major circulatory event at birth is an acute fall in pulmonary vascular resistance brought about by the onset of respiration and leading to an immediate increase in pulmonary blood flow. But the pulmonary vascular resistance remains elevated and the newborn infant is vulnerable to any form of hypoxic stimulus from delayed spontaneous respiration to birth asphyxia. Even a mild hypoxic stimulus can stimulate an exaggerated pulmonary vascular response with severe pulmonary vasoconstriction, leading to profound hypoxia and acidosis [8,9]. The hypoxia then becomes part of a vicious circle of worsening and life threatening vasoconstriction. There is severely reduced pulmonary blood flow and systemic flow is from right to left atrial and ductal shunting. Faced with newborn with severe cyanosis and oxygen saturation which may have fallen below 60% immediate resuscitation and administration of prostin and oxygen is needed. It will often be assumed that cyanotic heart disease is the cause. The abrupt increase in right ventricular work brought about by pulmonary vasoconstriction may cause subendocardial myocardial ischaemia and even infarction accompanied by tricuspid regurgitation. Echocardiography will exclude congenital heart disease, usually reveals a large PDA and may show not only right but also even left ventricular dysfunction. Enzyme and ECG changes of myocardial ischaemia will be discovered. Management of acute pulmonary hypertension is difficult but the principles are to ventilate, maintain oxygenation, ensure CO2 elimination, administer nitric oxide, consider intravenous prostacyclin and if necessary use inotropes.
3.6. Cardiovascular drugs
4.2. Acute ‘transient’ neonatal myocardial ischaemia and infarction
The approach to pharmacological therapy for acute circulatory failure has moved away from direct enhancement of myocardial contractility [7]. Rather than using specific inotropes, drugs with direct effects on peripheral vasculature have been employed as well. The goals are to optimise afterload while enhancing myocardial contractility with lower doses of inotropes and avoiding therefore unwanted increases in vascular resistance and myocardial oxygen consumption. Catecholamines and phosphodiesterase inhibitors are the mainstay of treatment.
This well recognised condition was first described in great detail by Richard Rowe [10,11] and there is little doubt it is under diagnosed by neonatologists and cardiologists. It typically arises as a consequence of perinatal birth asphyxia. Meconium staining of the liquor is common and the birth asphyxia is sometimes considered relatively mild. The clinical features are similar to those of myocarditis (tachypnoea and tachycardia with liver enlargement) although on echocardiography the right ventricle is more frequently involved because of subendocardial myocardial ischaemia secondary to severe persistent pulmonary hypertension. Again typical features are evidence of ischaemia or infarction on the ECG (Figs. 1–3) and cardiac enzymes are elevated. Cross-sectional echocardiography reveals significant tricuspid regurgitation and right and left ventricular dysfunction. There is often a good response to inotropic support and the prognosis is good in the majority with complete recovery and generation of new myocardium although ventricular arrhythmias and neonatal death may occur and prematurity is an additional risk factor for poor outcome.
3.7. Catecholamines Adrenaline increases heart rate and myocardial contractility but at higher does increases systemic vascular resistance although the effect is unpredictable. Noradrenaline causes systemic vasoconstriction and is useful in patients with extreme vasodilation but best avoided in patients with ventricular dysfunction. Dopamine increase myocardial contractility, heart rate and vascular tone and is useful at lower doses in infants with impaired ventricular function. Dobutamine increases myocardial contractility and heart rate and reduces systemic vascular resistance and benefits some infants in lower doses. Overall the response to catecholamines is somewhat unpredictable in part as a consequence of the multiple physiological effects. However they remain part of the first line therapy in acute circulatory failure.
4.3. Myocarditis When a mothers suffers from what is often an unremarkable viral illness during the last trimester, there is a small chance the newborn infant will have myocarditis with dilated cardiomyopathy [12]. The
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M.L. Rigby / Early Human Development xxx (2016) xxx–xxx
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Fig. 1. Normal ECG from a 4 day old infant showing usual T wave morphology.
consequence may be acute deterioration, tachycardia, tachypnoea, liver enlargement and the clinical picture of rapid onset congestive cardiac failure, low cardiac output and pulmonary oedema which might be misconstrued as acute respiratory distress syndrome. Support for the diagnosis is raised cardiac enzymes, generalised ECG T wave changes (Fig. 2), sometimes with evidence of myocardial infarction, cardiomegaly on
a chest radiograph and impaired left ventricular systolic and sometimes diastolic function on echocardiography. Intubation and ventilation and inotropic support are often required and ECMO occasionally but the prognosis is poor and aggravated by prematurity. Other forms of dilated cardiomyopathy acquired in utero also rarely present in the first days of life.
Fig. 2. ECG from a 7 day infant with myocarditis and myocardial infarction with typical S-T segment elevation in leads V1-V6 and leads 1 and aVL.
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Fig. 3. ECG from a 3 day old infant with a history of perinatal asphyxia. There is evidence of myocardial ischaemia/infarction with S-T segment elevation and depression.
4.4. Other causes of myocardial infarction or ischaemia
4.6. Cardiac arrhythmias
Coronary artery stenosis or atresia sometimes occurs in isolation but is usually found in hearts with pulmonary atresia and intact ventricular septum. In these cases fistulas communications between the right ventricle and coronary arteries may not provide adequate coronary flow resulting in impaired ventricular function with obvious ischaemia or infarction evident on an electrocardiogram. The prognosis is poor and characterised by the early development of cardiogenic shock; cardiac transplantation is the only treatment option. Coronary embolism in cyanotic heart disease or hearts with a right to left atrial shunt is rare and results from the inadvertent injection of thrombus or air through a venous cannula. Myocardial ischaemia usually resolves with supportive treatment. Although anomalous origin of a coronary artery from the pulmonary artery is an important cause of myocardial ischaemia/infarction, in term infants, symptoms rarely develop before the age of 6 weeks. The reason for this is a delayed fall in pulmonary artery pressure and vascular resistance maintaining adequate blood flow to the anomalous coronary. Only when the pulmonary artery pressure begins to approach normal levels is coronary perfusion inadequate causing ischaemia and subsequent life threatening infarction. All the usual clinical, laboratory, ECG and echocardiographic features will be present. Expert echocardiography also allows demonstration of the anomalous coronary artery origin. Premature infants who usually have a lower pulmonary vascular resistance develop severe circulatory failure earlier.
Supraventricular or atrial tachycardia beginning in the third trimester may continue after birth causing severe left ventricular dysfunction. If initial treatment with intravenous adenosine or cardioversion fails to establish sinus rhythm, consider amiodarone as the treatment of choice and if necessary administer adenosine again after 12 h. Beta blocking drugs are contraindicated in the presence of ventricular dysfunction.
4.5. Hypertrophic cardiomyopathy Rarely some forms of hypertrophic cardiomyopathy acquired antenatally may present soon after birth with acute circulatory failure. Examples include those associated with Noonan's syndrome and Pompe's disease but other types are also described. Such an early presentation is indicative of an extremely poor outcome whatever treatment option is used.
4.7. Cardiac tamponade A pericardial effusion with cardiac tamponade is rare immediately after birth but may be a consequence of foetal heart failure or hydrops and viral pericarditis. The cardiac causes of hydrops include severe tricuspid regurgitation, critical aortic stenosis and antenatal tachyarrhythmias. Spontaneous perinatal pneumopericardium will produce a similar clinical picture of low cardiac output, tachycardia, hypotension and liver enlargement but in addition to cardiomegaly on the chest X ray, air will be evident around the heart. Echocardiography establishes the presence of a large pericardial effusion and any associated cardiac anomalies. Immediate pericardiocentesis can be life-saving and should not be delayed; if possible use ultrasound screening, insert a small gauge needle with a subxiphoid approach and aspirate the straw colours fluid or air. With a 22 gauge needle, inadvertent puncture of the heart will not cause life threatening bleeding. In addition a soft 0.018 guide wire, readily available on a neonatal unit, can be passed through the cannula when it occupies a satisfactory position in the pericardial space; a larger cannula can then be used to replace the smaller one allowing a more efficient aspiration. 4.8. Final comments Thus there are many conditions with the capacity to cause acute circulatory failure or severe hypoxia in the neonate. An awareness of the possibilities, a high index of suspicion, an ability to interpret physical
Please cite this article as: M.L. Rigby, Best practice critical cardiac care in the neonatal unit, Early Hum Dev (2016), http://dx.doi.org/10.1016/ j.earlhumdev.2016.09.003
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Please cite this article as: M.L. Rigby, Best practice critical cardiac care in the neonatal unit, Early Hum Dev (2016), http://dx.doi.org/10.1016/ j.earlhumdev.2016.09.003