This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: ECG and Arrhythmias 1, Subject name: Medicine
[{'content': 'A 50 year old breast cancer patient presents with breathlessness. What does the ECG show? \nSelect and explain. \nA. Normal tracing, B. AV dissociation, C. Electrical Alternans, D. Electromechanical dissociation', 'role': 'user'}, {'content': 'Answer: C \nExplanation: HR is about 150/min with variation in electrical axis due to fluctuation in amplitude of QRS complex on beat to beat variation. Malignancies like breast cancer and lung cancer can metastasize to the hea leading to cardiac tamponade.', 'role': 'assistant'}]