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
The ECG of a 40 year old male was recorded using standard bipolar limb leads. The sum of voltage of the three standard leads was found to be 5 millivolts. This indicates: 
Select and explain. 
A. A normal hea, B. Right ventricular hyperophy, C. Left ventricular hyperophy, D. Increased cardiac muscle mass
D: Increased cardiac muscle mass
Answer: D: Increased cardiac muscle mass 
Explanation: D i.e. Increased cardiac muscle massWhen the sum of voltages of all the QRS complexes of the three standard leads is greater than 4 millivolts, the ECG is considered as high voltage electrocardiogram. Most often due to increased cardiac muscle massQ.The voltage in the three standard leads is measured from the peak of R wave to the bottom of S wave = 0.5 - 2.0 millivoltsHighest voltage is in lead II, lowest in lead III.