Though ECG is a simple bedside investigation which is widely available and has been in use for more than a century, it has a low sensitivity and specificity on many occasions. In the case of coronary artery disease, even severe triple vessel disease can be present with a normal ECG. This in spite of the fact that there are very few tests which surpasses the ECG in the diagnosis of an acute myocardial infarction at the bedside and even out of hospital. All mild valvular lesions and small intra cardiac shunts can have normal ECG. Normal ECG in can be present in traumatic rupture of the heart as well, though it is a lethal situation. In many of the electrical disorders of the heart, also known as channelopathies, ECG can be normal at times because of spontaneous fluctuation in ECG patterns. For example the ECG in Brugada syndrome may manifest the diagnostic features only with drug challenge with Flecainide or during a febrile illness. In long QT syndromes the ECG at baseline may be showing a near normal QT interval with paradoxical QT prolongation with exercise. The baseline ECG in catecholaminergic ventricular tachycardia may be normal, though life threatening ventricular arrhythmias can occur with exercise or emotional stress.