Cardiac Arrest in a Newborn

A previously healthy 12-day-old boy was admitted to the emergency department due to sudden cardiac arrest with 10 minutes of evolution. The parents report that the infant was in the car seat when he suddenly began to cry inconsolably and eventually collapsed in his father's arms. He is the first child of a non-consanguineous couple and was born at 38 weeks' gestational age by cesarean delivery due to breech presentation. The pregnancy was uncomplicated. Apgar scores were 9 and 10 at the first and fifth minute, respectively, and birth weight was 2700 g (12th percentile (P12)). He only required normal newborn care, and screening results for critical congenital heart defects were negative. He was discharged from the hospital on the second day after birth, on exclusive breastfeeding. On day 7 of life, he had an unremarkable physical examination at a pediatric appointment.According to the parents, he frequently spit up and had last fed 2 hours before the event. There were no signs of cough or other symptoms, and no other household members were reported to be ill.At the emergency department, he was bradycardic and apneic. Chest compressions were initiated, followed by endotracheal intubation. Circulatory support was given by intravenous fluids (normal saline fluid bolus) and started on inotropes (dopamine, dobutamine, and adrenaline). Blood glucose level was 56 mg/dL, and arterial blood gas demonstrated severe lactic acidosis (pH, <6.8; HCO3−, unmeasurable; serum lactate, >15 mmol/L; base excess [BE], unmeasurable; pCO2, 54.9 mm Hg).He also received intravenous bicarbonate for correction of metabolic acidosis and was started on empirical ampicillin and cefotaxime.He was transferred to a level III neonatal intensive care unit (NICU) for further management and evaluation. On arrival, the newborn presented with axillary temperature of 38 °C, heart rate of 191 beats per minute, respiratory rate of 79 breaths per minute, and noninvasive blood pressure measurement of 54/33 mm Hg, with a mean arterial pressure of 42 mm Hg. General examination revealed poor overall condition, gray discoloration of the skin, palpable soft hepatomegaly of 3 cm below the costal margin, and weak peripheral pulses.Blood workup demonstrated elevated cardiac enzymes and abnormal liver test results (Table). The C-reactive protein concentration was 0.33 mg/dL. The full blood count and the serum electrolytes and ammonia concentrations were within normal range. An arterial blood gas sample showed pH of 7.29; pCO2, 18 mm Hg; pO2, 116 mm Hg; HCO3, 8.4 mm Hg; BE, −15.6; and lactate, 9.5 mmol/L.Chest radiography showed only a slight cardiomegaly. Twelve-lead electrocardiography revealed right axis deviation (147°), QS complexes in V5 and V6, and generalized ventricular repolarization abnormalities. Echocardiography (Figure 1) revealed left atrial and ventricular dilatation, moderate mitral regurgitation, moderate-to-severe systolic dysfunction of the left ventricle (ejection fraction, <40%), and suprasystemic pulmonary hypertension (estimated pulmonary artery systolic pressure, 76 mm Hg), with no structural heart disease.The differential diagnosis for sudden cardiac arrest in a previously healthy newborn includes the following: Myocardial diseaseArrhythmiaMyocarditisStructural congenital anomalies ○ Congenital heart disease○ Anomalous left coronary artery from the pulmonary artery (ALCAPA syndrome)InfectionInborn errors of metabolismThe newborn underwent computed tomography angiography to exclude ALCAPA syndrome, which showed normal origin and proximal course of the coronary arteries.Cranial ultrasonography showed no signs of hemorrhage or other abnormalities. The electroencephalogram showed brain immaturity with a discontinuous pattern and reduced cyclicity, with signs of left hemispheric dysfunction.Although there were no respiratory symptoms, a nasopharyngeal swab was performed and yielded positive results for enterovirus. Blood polymerase chain reaction (PCR) examination also had positive results.Based on the echocardiography findings, elevated cardiac enzymes, positive viral cultures, and exclusion of other causes, a diagnosis of viral myocarditis was assumed. The neonate's condition improved within the first week after admission, with inotropic support discontinued on the second day and ventilatory support withdrawn on the fourth day of hospitalization. A single dose of immunoglobulin (750 mg/kg) was administered.Brain magnetic resonance imaging (MRI) showed subtle signal changes with restricted diffusion, suggestive of acute/subacute hypoxic-ischemic lesions.Acute viral myocarditis (enterovirus).Cardiac arrest in newborns is a rare but critical event characterized by the sudden cessation of effective circulation.1The most common causes of primary cardiac arrest in newborns are cardiomyopathy, congenital heart anomalies, and/or arrhythmias, while secondary causes include perinatal asphyxia, sepsis, metabolic imbalances, hypovolemia, and hypothermia.2,3Myocarditis is a severe condition characterized by inflammation of the heart muscle, most commonly caused by viral infections but also with bacterial and fungal infections, autoimmune diseases, metabolic disorders, or toxin exposure as potential etiologies.4From a clinical standpoint, neonatal myocarditis often mimics bacterial sepsis, presenting with symptoms such as lethargy, feeding difficulties, tachycardia, respiratory distress, and poor peripheral perfusion. Severe cases may progress to congestive heart failure, cardiogenic shock, and arrhythmias, often progressing rapidly if untreated.5,6Enteroviruses are the most frequent causative agents at this age, transmitted vertically during delivery or postnatally. Neonates are particularly vulnerable, with infections typically occurring in the first 2 weeks of life.5,7,8The diagnosis of myocarditis is suggested by signs of ischemia on 12-lead electrocardiogram, elevated cardiac enzymes levels, and left ventricular dysfunction on echocardiography with normal coronary artery origin.5 Endomyocardial biopsy was classically the gold standard for diagnosis; however, it is rarely used due to its invasiveness, being reserved only for selected cases.9 Cardiovascular MRI (CMRI) is a noninvasive tool that can detect myocardial edema, inflammation, and fibrosis while assessing cardiac structure and function.9 Although currently the most widely used diagnostic method for myocarditis, CMRI presents important limitations and pitfalls in neonates.4,10The management of neonatal myocarditis is primarily supportive, as there are no specific antiviral therapies available when a viral etiology is identified.11 PCR testing is the preferred method for identifying viral RNA in blood or other specimens.5 In case of failure of conventional treatment, extracorporeal membrane oxygenation (ECMO) may be used as a temporary measure to support recovery.12 Intravenous immunoglobulins are frequently used in cases of severe neonatal enteroviral myocarditis; however, there are limited data to support this therapy.13Despite advances in neonatal care, the prognosis for neonatal myocarditis remains poor, with reported mortality rates reaching up to 50%-60% in severe cases.5,8 Survivors often require ongoing cardiac therapy, including angiotensin-converting enzyme inhibitors, beta-blockers, or diuretics, along with regular follow-up through echocardiography or CMRI to monitor myocardial recovery and function.9,10Evaluation on the day before discharge showed a progressive decrease in cardiac enzyme levels (troponin I, 161.6 ng/L; creatine kinase–MB, 1.4 ng/mL; and myoglobin, 7.1 ng/mL) and mild to moderate left ventricular dysfunction, with hypokinesia of the mid-basal septal segments. Subsequent outpatient evaluations revealed a progressive recovery of cardiac contractility (left ventricular ejection fraction [LVEF], 58%), with the patient always remaining asymptomatic.At 2 months, CMRI (Figure 2) showed preserved biventricular systolic function (LVEF, 54%; right ventricular ejection fraction, 68%) and transmural late enhancement in the mid-apical lateral segments and the anterior apical segment, consistent with fibrosis. At the last follow-up, at 11 months, the patient presented with normal neurodevelopment.Although an underrecognized etiology of cardiac arrest, myocarditis can be a devastating disease with high mortality rates.Enteroviruses are the most common agents, and viral myocarditis should be considered in neonates with sudden myocardial dysfunction without structural congenital malformations.For infants diagnosed with myocarditis, regular follow-up with a cardiac specialist is mandatory to assess cardiac remodeling and potential recovery of left ventricular function.Efforts to prevent viral infection during the perinatal period are crucial, given the severity of the disease and limited treatment options.American Board of Pediatrics Neonatal-Perinatal Content SpecificationUnderstand cardiomyopathies and treatment in the NICURecognize perinatal and postnatal viral infectionsKnow various indications, management, and complications of medical technology (eg, central lines, gastronomy, tracheostomy, ostomy, ventriculoperitoneal shunt, ECMO) as they pertain to cardiac arrest and resuscitation in a newborn