Case 3: Bradycardia in a Vigorous Newborn

A female infant is delivered at 38 weeks and 3 days to a 32-year-old gravida 2, para 1 woman via a low transverse cesarean section. At delivery, the neonate is noted to have a spontaneous cry, appropriate respiratory effort, and active movement of all extremities; however, her initial heart rate is noted to be 40 beats/min.After drying and stimulation, her oxygen saturation on pulse oximetry is noted to remain at 60% at 3 minutes after birth. Blow-by oxygen is started. Despite this intervention, she develops nasal flaring and subcostal retractions. Facial continuous positive airway pressure (CPAP) is initiated with positive end-expiratory pressure of 5 mm Hg and then the infant is transitioned to nasal CPAP. Oxygen concentration is titrated to 100% and oxygen saturations on pulse oximetry increase to greater than 90%. Her work of breathing normalizes. Apgar scores are noted to be 6 and 8 at 1 and 5 minutes, respectively.Despite effective ventilation and oxygen saturations, the infant’s heart rate remains between 40 and 50 beats/min. A 12-lead electrocardiogram is obtained, which confirms the diagnosis (Fig 1).This infant’s presentation was concerning for a cardiac anomaly, given the intractable bradycardia despite adequate respiratory support, and oxygen saturations. Electrocardiographic findings were consistent with complete heart block (congenital atrioventricular block, third degree). She began receiving an isoproterenol infusion starting at 0.15 μg/kg per minute to increase ventricular rate.On day 1 after birth, isoproterenol was discontinued to obtain baseline hemodynamics and heart rate, which remained at approximately 40 beats/min. Her systolic blood pressures averaged between 60 and 70 mm Hg and her diastolic blood pressures averaged between 25 and 35 mm Hg.By day 2 after birth, she was transferred to the pediatric cardiac intensive care unit; the pediatric cardiothoracic surgeon carried out a minimally invasive placement of a single right ventricular epicardial bipolar pacing lead and generator using a subxiphoid approach. The pacemaker mode was VVI at a rate of 80 beats/min. Her remaining hospital course was uneventful and she was discharged from the hospital with her family on day 5 after birth.Maternal and antenatal history was significant for maternal autoimmune arthritis with antibody positivity for anti-SSA/Ro and anti-SSB/La antibodies. The infant’s mother also had been treated with thyroid hormone replacement therapy for hypothyroidism.In this case, fetal echocardiography performed at 13 weeks of gestation revealed complete heart block (CHB) and large ascites. The mother was started on terbutaline to increase fetal heart rate and dexamethasone to prevent maternal antibody-mediated myocarditis. Serial echocardiography demonstrated CHB at 20, 24, and 28 weeks of gestation with resolution of ascites by 34 weeks of gestation.Neonatal lupus syndrome is an acquired autoimmune disease that occurs in some infants born to mothers with anti-SSA/Ro and anti-SSB/La antibodies associated with a range of autoimmune disorders, including systemic lupus erythematosus, Sjögren syndrome, idiopathic inflammatory myopathies, systemic sclerosis, mixed connective tissue disease, and rheumatoid arthritis. (1)(2) The condition is characterized by congenital heart block, cardiomyopathy, cutaneous lupus lesions, hepatobiliary disease, thrombocytopenia, or other hematologic cytopenias either independently or concurrently. (3)(4)(5)The most concerning complication is neonatal CHB, which has a prevalence of about 1% to 2% in infants of anti-SSA/Ro–positive mothers, and a recurrence rate of approximately 17% in subsequent pregnancies. (6) Neonatal lupus accounts for 90% to 95% of CHB cases occurring in utero or during the neonatal period. (4)(7)(8)Cutaneous features of neonatal lupus, which may be apparent at the time of delivery or after the newborn has been discharged from hospital, include multiple erythematosus annular lesions or arcuate macules. The rash is often described as a raccoon-eye appearance, with the face being the most common site affected, followed by the palms, soles, or diaper area (Fig 2). (3)(5)(9)Anti-SSA/Ro and anti-SSB/La autoantibodies are transplacentally transmitted during the second trimester. (10) It is thought that CHB occurs because of opsonization of anti-SSA/Ro and anti-SSB/La autoantibodies to neonatal cardiocytes in utero, thereby inhibiting these cells from participating in the usual clearance of apoptotic cardiocytes. This results in an accumulation of apoptotic cells, promoting inflammation, remodeling, and fibrosis, which may lead to myocarditis or cardiac rhythm impairment. (10)Because CHB usually develops between 18 and 24 weeks of gestation, some experts recommend serial fetal echocardiography during this period, with premature atrial contractions and moderate pericardial effusions being concerning for the potential development of CHB. If first- or second-degree heart block is noted on fetal echocardiography, maternal treatment with steroids may prevent progression to CHB. If CHB is detected, treatment with dexamethasone may be initiated to prevent myocarditis, not to treat CHB, because myocarditis is an irreversible complication. (11)(12) The evidence regarding the efficacy of fluorinated steroids in the prevention of mortality in CHB is inconsistent with concerns for adverse effects during pregnancy. (13) In addition, sympathetic β-agonists have been used to increase fetal heart rates in utero, but evidence regarding their impact on mortality is limited. (13)The authors wish to acknowledge Dr Dawn Davis, Associate Professor of Dermatology and Pediatrics, Mayo Clinic, Rochester, MN, for providing the photograph of the neonatal lupus rash.