This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: All India exam, Subject name: Microbiology
Morris Index positive in ECG is suggestive of 
Select and explain. 
A. Right atrial enlargement, B. Left atrial enlargement, C. Right ventricular hyperophy, D. left ventricular hyperophy
B: Left atrial enlargement
Answer: B: Left atrial enlargement 
Explanation: The index proposed by Morris (amplitude of the negative deflection in V1 in mm multiplied by its duration in seconds) is positive if greater than 0.03Morris Index positive in ECG is suggestive of Another sign of Left atrial enlargement in ECG is P wave width >2.5 mm in lead II.Right, atrial enlargement P wave height >2.5mm in lead II and area of the Positive phase of P wave in Lead V1 >0.06mmsec.