This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Physiology
[{'content': 'The ECG of a 40 year old male was recorded using standard bipolar limb leads. The sum of the voltage of the three standard leads was found to be 5 millivolts. This indicates: \nSelect and explain. \nA. A normal heart, B. Right ventricular hypertrophy, C. Left ventricular hypertrophy, D. Increased cardiac muscle mass', 'role': 'user'}, {'content': 'Answer: D \nExplanation: “When the sum of the voltages of all the QRS\xa0complexes\xa0 of\xa0 the\xa0 three\xa0 standard\xa0 leads\xa0 is\xa0greater than 4 mV, the patient is considered\xa0to\xa0 have\xa0 a\xa0 high-voltage\xa0 electrocardiogram.\xa0The\xa0 cause\xa0 of\xa0 high-voltage\xa0 QRS\xa0 complexes\xa0most\xa0 often\xa0 is\xa0 increased\xa0 muscle\xa0 mass\xa0 of\xa0the\xa0 heart,\xa0 which\xa0 ordinarily\xa0 results\xa0 from hypertrophy of the muscle.” So, in general\xa0 its\xa0 hypertrophy\xa0 of\xa0 heart\xa0 (may\xa0 be\xa0 right\xa0 or,\xa0left ventricular), but you cannot determine\xa0whether it is due to right or, left ventricular\xa0hypertrophy.', 'role': 'assistant'}]