A 67-year-old man with a history of bicuspid aortic valve presents to the emergency department after experiencing syncope during his morning jog. He reports progressive dyspnea on exertion over the past 6 months. Vital signs show BP 138/82 mmHg, HR 78 bpm, RR 16/min. Physical examination reveals a harsh, crescendo-decrescendo systolic ejection murmur best heard at the right upper sternal border with radiation to bilateral carotids. The carotid upstroke is delayed and diminished bilaterally. Echocardiography confirms severe aortic stenosis with an aortic valve area of 0.6 cm² and normal left ventricular systolic function at rest. Which of the following best explains the pathophysiology of his exertional syncope?

1. A)Vasovagal reflex triggered by a paradoxical rise in left ventricular pressure that activates left ventricular mechanoreceptors
2. B)Acute pulmonary edema causing severe hypoxemia and altered cerebral metabolism during exertion
3. C)Fixed cardiac output that cannot increase appropriately with exercise, resulting in inadequate cerebral perfusion pressureGABARITO
4. D)Atrial fibrillation with rapid ventricular response causing hemodynamic collapse
5. E)Coronary steal phenomenon from severe aortic stenosis reducing left anterior descending artery perfusion