This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Disease of pericardium, Subject name: Medicine
[{'content': 'Which of the following describes the marked ECG finding? \nSelect and explain. \nA. T-wave alternans, B. Electrical alternans, C. Electromechanical dissociation, D. All of the above', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Notice the low voltage ECG which is defined as amplitude of all qRS complexes in limb leads less than 5 mm. Also notice that amplitude of qRS complexes is variable in all the arrow marked leads. Hence, the ECG is diagnostic of electrical alternans. The triad of sinus tachycardia with low voltage ECG and electrical alternans is highly suggestive of pericardial effusion.', 'role': 'assistant'}]