A previously healthy 19-year-old man is brought to the emergency department by his girlfriend after briefly losing consciousness. He passed out while moving furniture into her apartment. She said that he was unresponsive for a minute but regained consciousness and was not confused. The patient did not have any chest pain, palpitations, or difficulty breathing before or after the episode. He has had episodes of dizziness when exercising at the gym. His blood pressure is 125/75 mm Hg while supine and 120/70 mm Hg while standing. Pulse is 70/min while supine and 75/min while standing. On examination, there is a grade 3/6 systolic murmur at the left lower sternal border and a systolic murmur at the apex, both of which disappear with passive leg elevation. Which of the following is the most likely cause?
AProlonged QT interval
BHypertrophic cardiomyopathy
CMitral valve stenosis
DMitral valve prolapse
EBicuspid aortic valve
A researcher measures action potential propagation velocity in various regions of the heart in a 42-year-old Caucasian female. Which of the following set of measurements corresponds to the velocities found in the atrial muscle, AV Node, Purkinje system, and ventricular muscle, respectively?
A0.05 m/s, 1.1 m/s, 2.2 m/s, 3.3 m/s
B2.2 m/s, 0.3 m/s, 0.05 m/s, 1.1 m/s
C0.3 m/s, 2.2 m/s, 0.05 m/s, 1.1 m/s
D0.5 m/s, 1.1 m/s, 2.2 m/s, 3 m/s
E1.1 m/s, 0.05 m/s, 2.2 m/s, 0.3 m/s
A 23-year-old man comes to the emergency department because of palpitations, dizziness, and substernal chest pain for three hours. The day prior, he was at a friend’s wedding, where he consumed seven glasses of wine. The patient appears diaphoretic. His pulse is 220/min and blood pressure is 120/84 mm Hg. Based on the patient's findings on electrocardiography, the physician diagnoses atrial fibrillation with rapid ventricular response and administers verapamil for rate control. Ten minutes later, the patient is unresponsive and loses consciousness. Despite resuscitative efforts, the patient dies. Histopathologic examination of the heart at autopsy shows an accessory atrioventricular conduction pathway. Electrocardiography prior to the onset of this patient's symptoms would most likely have shown which of the following findings?
AEpsilon wave following the QRS complex
BProlongation of the QT interval
CCyclic alteration of the QRS axis
DSlurred upstroke of the QRS complex
EPositive Sokolow-Lyon index
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