A 4-months old male toddler is referred to the pediatric emergency department for sepsis. The infant presents with tachypnea and tachycardia, pale & sweaty. Mild intercostal retractions can be noticed. SpO2 is 97% in room air, the infants breathes spontaneously. Initial blood screen shows pH 7.17, Lactate 5.0. The mother reports mild diarrhea, no history of fever, but reduced fluid intake over the past 24 hours. Emergency Medical Services (EMS) reports preclinical heart rates of 300 bpm. On the ECG you see the following:
The ECG can be interpreted as Narrow Complex Tachycardia (NCT) at 270-280 bpm. Fluid bolus at a total of 20 cc is administered as iv push, showing no clinical response or change in heart rate. Another 10 cc fluid bolus are administered and the infant is started on Dexmedetomidin for mild sedation. Meanwhile the pediatric cardiologist on call arrived and the infant spontaneously converts into sinus rhythm at 140 bpm. The ECG is shown below:
There is clear preexcitation present, with short PR interval and a positive Delta-wave in leads I and aVL. Wolff-Parkinson-White syndrome just became very likely the reason for tachycardia.
Lab values came back negative for infection, no further signs of sepsis could be found.
On echocardiography fluid status was balanced and, aside from a minor atrial septal defect type II, there were no structural or functional abnormalities to be found.
The patient was started on beta blockers for prophylaxis and since remained in sinus rhythm.
Furthermore, the ECGs of the patient tell us the location of the accessory pathway. most probable it is located Left Postero Septal (positive Delta-wave in V1, negative Delta-wave in all inferior leads, V1/I ratio <1; according to Pambrun et al (1). The ECGs also tell us that the accessory pathway conducts in both, anterograde and retrograde direction. Anterograde conduction is shown by manifest preexcitation in the resting ECG during sinus rhythm. Preexcitation results from the atrial impulse reaching the ventricle faster over the accessory pathway (AP) than over the AVN-His Purkinje system. Tachycardia was orthodromic (narrow complex tachycardia). Therefore, during tachycardia the impulse travels anterograde over the AV node and retrograde over the AP.
(1) Pambrun T, El Bouazzaoui R, Combes N, Combes S, Sousa P, Le Bloa M, Massoullié G, Cheniti G, Martin R, Pillois X, Duchateau J, Sacher F, Hocini M, Jaïs P, Derval N, Bortone A, Boveda S, Denis A, Haïssaguerre M, Albenque JP. Maximal Pre-Excitation Based Algorithm for Localization of Manifest Accessory Pathways in Adults. JACC Clin Electrophysiol. 2018 Aug;4(8):1052-1061.)