From where i will get detailed information of e.c.g. changes in left ventricular failure?

No where : Lv failure (i assume you mean reduced pumping power) does not result in any specific ECG findings. In fact, the ECG can look completely normal! on the other hand, in many patients, a whole range of abnormalities can be seen, including evidence of prior heart attacks (myocardial infarctions), conduction system disease, thickening of the heart muscle (hypertrophy), etc. See your doctor.