in ecg, why electrical lead is attached to left ankle and not right?
ECG or electrocardiogram is device that measures the electrical activity of the heart. Willem Einthoven was a Dutch doctor and physiologist. He invented the first practical electrocardiogram (ECG or EKG) in 1903 and received the Nobel Prize in Medicine in 1924 for it. Usually more than 2 electrodes are used and they can be combined into a number of pairs For example: Left arm (LA), right arm (RA) and left leg (LL) electrodes form the pairs: LA+RA, LA+LL, RA+LL). The output from each pair is known as a lead. The combination of these limbs (LA+RA+LL) forms an imaginary equilateral triangle with the heart at its center. This is known as Einthoven's triangle. The choice of limbs (LA+RA+LL) is done in such a way that the heart lies exactly at the center of the Einthoven's triangle.
Hope this helps to clear your doubt,