A 17-Year-Old Boy Is Brought to the Emergency Department After

A 17-year-old boy is brought to the emergency department after passing out.  The patient was standing behind the dugout watching his friends play baseball when he suddenly felt warm and light-headed.  Then he remembers awakening on the ground.  Bystanders reported that the patient was unresponsive for approximately 2 minutes.  He feels fatigued but does not have chest pain or shortness of breath.  The patient has no significant medical history and does not use alcohol or drugs.  Temperature is 36.7 C (98.1 F) , supine blood pressure is 105/60 mm Hg and standing blood pressure is 110/65 mm Hg, pulse is 84/min, and respirations are 16/min.  Pulse oximetry is 100% on room air.  The patient is awake and alert.  Pupils are equal and reactive.  Heart and lung examinations are normal.  The abdomen is soft and nontender.  Neurologic examination is normal.  ECG is unremarkable.  Which of the following is the most likely cause of this patient's syncope?

A) Increased automaticity of the Purkinje fibers
B) Increased parasympathetic output to the heart
C) Increased sympathetic output to the small vessels
D) Reentry arrhythmia using the atrioventricular node
E) Systolic anterior motion of the mitral valve

Correct Answer:

Verified

Unlock this answer now
Get Access to more Verified Answers free of charge

Access For Free