Case:
A 3 week old, previously healthy male infant is referred to the emergency department after presenting to his well-child appointment with mom and found to be bradycardic. Patient is meeting all growth/length milestones to this point and had no recent illnesses. Mom is otherwise healthy and had an uneventful pregnancy, ending in normal spontaneous vaginal delivery at 39 weeks. On presentation, patient is afebrile, hemodynamically stable, and in no respiratory distress. Patient is alert and well-appearing. He is feeding without issue, has cap refill of 2 sec, is warm, and has a soft fontanelle.
EKG shown below:
Interpretation: Bradycardia, high grade AV block with 3:1 conduction, far-right axis deviation, normal pediatric R wave progression, no ST or T wave abnormalities
What next:
A well appearing infant with bradycardia should immediately have an EKG obtained to evaluate for pathologic bradyarrhythmias. At first glance at this ECG, one could easily conclude that this is a complete heart block. However, on closer examination, there is not a complete AV dissociation. There is a consistent 3:1 conduction pattern except for the 7th beat, which is conducted after the second atrial beat. This 2:1 beat has a slightly longer PR interval than the other beats, however it is still within normal limits and can be assumed to have originated from the atrial depolarization.
Congenital heart block is a rare neonatal condition that is overwhelmingly caused by intrauterine exposure to maternal autoantibodies related to SLE or Sjogren’s syndrome, accounting for 60-90% of cases. Patients typically present at a mean age of 5 years of age. Less commonly, structural heart disease has been described as a cause, which, interestingly, was the case for our patient who was found to have a noncompaction of the left ventricle (aka “spongiform” cardiomyopathy). Bedside echocardiography was obtained and a representative image is shown below
Image from: https://www.youtube.com/watch?v=1jvKM5Bog6Y
This is a parasternal short view demonstrating the bizarre appearance of the LV. Note the many trabeculations in the LV myocardium, consistent with non-compaction. RV appears to be normal in size. Patients with this type of congenital malformation are at high risk of complete heart block due to the displacement of the AV node during endocardial cushion development in utero.
Patients who present in the neonatal period are typically stable with a nonspecific presentation, though some can have signs of hemodynamic instability or respiratory distress. Patients presenting later in childhood will present with reduced exercise tolerance or syncope. More than 90% of patient found to have congenital heart blocks end up receiving a permanent pacemaker during their lifetime.
Management:
Airway, breathing and circulation should first be confirmed to be intact. Transcutaneous pacing pads should be placed in anticipation of potential worsening of bradycardia. Pediatric cardiology consult should be obtained, if available. Bedside echocardiography should be obtained to assess for structural abnormalities and signs of congestive heart failure. Auto-immune labs should be obtained, especially if there is a maternal history of SLE or Sjogren’s. Admission or transfer to a comprehensive pediatric cardiac ICU should be advocated for as these patients are at high risk for decompensation. With our patient, his EKG showed a heart rate of 66, clearly a dangerously slow rate for a child of 3 weeks. The patient was admitted to the Pediatric CCU and subsequently received permanent pacemaker placement.
Written by:
Alex Alanis, MD
Emergency Medicine Resident, PGY-3
Cook County Health
Reviewed by:
Tarlan Hedayati, MD
Chair of Education
Cook County Health
References:
https://radiopaedia.org/articles/non-compaction-of-the-left-ventricle-1?lang=us
Kusumoto FM, et al., 2018 ACA/AHA/HRS Guideline on the Evaluation and Management of Patients with Bradycardia and Cardiac Conduction Delay: A report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines and the Heart Rhythm Society. J Am Coll Cardiol. 2019;74(7):e51