A 26-year old male comes to the emergency room complaining of syncope. He passed out while exercising in the gym. His father died of sudden cardiac death in his early 40s. Physical examination is significant for paradoxical splitting of second heart sound, S4 gallop, sustained apical impulse and a systolic ejection murmur at left lower sternal border. The murmur increased with the Valsalva maneuver. Patient was admitted for investigative studies. ECG revealed left ventricular hypertrophy with exaggerated septal Q waves. Echocardiogram showed asymmetrical thickening of the interventricular septum, resulting in dynamic obstruction of the LV outflow tract and abnormal systolic motion of the mitral valve. Which of the following medications should be avoided in this patient?
