No.The first thing to understand is that an ECG is not used for diagnosing a blocked artery;it's used to find out the heart's beating patterns,detects wall thickening(hypertrophy),detect heart attacks,new and old.An angiogram actually goes into the arteries and takes pictures to detect blockages. An echo-cardiogram can also be used in combination with the Doppler monitoring technique,to measure blood flow through the heart chambers,as well as flow through the pressure gradients across valves to determine the degree of narrowing.