ECG indicates the overall rhythm of the heart and weaknesses in different parts of the heart muscle. It is the best way to measure and diagnose abnormal rhythms of the heart. ECG can identify damaged heart muscle. But it can only identify damage to muscle in certain areas, so it can’t rule out damage in other areas. The ECG cannot reliably measure the pumping ability of the heart; for which ultrasound-based echocardiography is used.