The hot morning sun glared through the window as Lynn sat intently listening to her kindergarten teacher read their morning story. Suddenly, Lynn clenched her chest and apruptly announced, "My chest hurts!"
Realizing that lunch time was near, and knowing that Lynn was a perfectly healthy five year old, the teacher encouraged Lynn to relax, suggesting she would feel better after eating. Lynn persisted with, "But, you don't understand....my heart is going too fast." The teacher saw the look of terror on Lynn's suddenly pale face, and summoned the school nurse at once.
Upon arrival, the nurse noted that Lynn appeared just as the teacher had described, and additionally noted there was no evidence of respiratory distress, the child was able to speak in full sentences, and her skin was warm and dry. The nurse immediately palpated a radial pulse which was found to be a mere quivering pulsation that was impossible to count. The nurse then auscultated Lynn's apical heart rate, and was quite surprised when she counted a rate of 236 beats per minute!
The school nurse notified the nearest pediatric emergency department of Lynn's impending arrival, so they were prepared for her as she was carried through the door. An antecubital fossa IV was inserted, while baseline vital signs were obtained, and the cardiac monitor was placed. She was immediately treated with a rapid IV bolus of adenosine at the standard dose of 0.1 mg/kg. (The ER staff estimated Lynn's weight to be 20 kg, therefore she received 2 mg. of adenosine). She converted to a sinus tachycardia at a rate of 120 bpm, and slowly settled into a normal sinus rhythm at a rate of 90. She was started on digoxin by mouth. Lynn's parents were given discharge instructions, including digoxin dosages (0.125 mg. of digoxin every morning and 0.0625 mg. before bed) and how to be alert for possible signs of digitalis toxicity in Lynn.
While obtaining a detailed history from Lynn's parents, the consulting pediatric cardiologist in the emergency department determined that Lynn most likely had this tachyarrhythmia since infancy. She had been evaluated at 3 months of age by her primary care provider for frequent vomiting, and by a cardiologist for episodes of pallor at 3 months of age and again at 2 years. All evaluations found nothing unusual for Lynn. In hindsight, however, this cardiologist determined that Lynn followed the course of the 35% of children who present with PSVT in infancy and again in early childhood.
Through meticulous avoidance of the precipitating factors of PSVT (chocolate, caffeine, "cold" preparations, and dehydration), Lynn was able to return to her usual activity without fear of chest pain or a fast heart rate. This period of adjustment took about 3 months and included the teaching of her immediately family, extended family, teachers, and all other care givers on how to avoid PSVT and how to care for any episodes that might occur.
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An episode of PSVT generally begins while the child is actively involved in vigorous play or exercise.