This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Respiratory system, Subject name: Medicine
[{'content': 'Pulsus alternans is seen in \nSelect and explain. \nA. Severe ventricular dysfunction, B. HOCM, C. AS, D. CP', 'role': 'user'}, {'content': "Answer: A \nExplanation: Pulses alterans is defined by beat-to-beat variability of pulse amplitude.It is seen in patients with severe left ventricular dysfunction and systolic hea failure,and is thought to be due to cyclic changes in intracellular calcium and action potential duration. Hyperophic obstructive cardiomyopathy is characterised by jerky pulse (pulses bisferens). Aoic stenosis is characterised by slow rising carotid pulse.(pulses parvus et tarsus) AS may also have anacrotic pulse Harrison's Medicine-20 the edition.", 'role': 'assistant'}]