A 26-year-old female is evaluated for palpitations and fatigue of several months duration. Her symptoms are present at rest and aggravated during light activityincluding climbing stairsand walking quickly. A 12-lead electrocardiogram (EKG) is notable for sinus tachycardia with a normal P-wave axis. Which of the following conditions is most likely to be associated with her symptoms and EKG findings?
a) Atrial fibrillation
b) Sinus node dysfunction
c) Premature atrial contractions
d) Supraventricular tachycardia
