inversion can also exists in leads III and aVF. Inversion of T waves in most of the ECG leads except aVR indicates many causes most commonly myocardial ischaemia and intracranial haemorrhage. Others include: hypertrophic cardiomyopathy, Takotsubo cardiomyopathy (stress-induced cardiomyopathy), cocaine abuse, pericarditis, pulmonary embolism, and advanced or complete atrioventricular block. Frequency of inverted T-waves Numbers from Lepeschkin E in Biphasic T wave As the name suggests, Biphasic T waves move in opposite directions. The two main causes of these waves are myocardial ischemia and hypokalemia. Ischemic T waves rise and then fall below the cardiac resting membrane potential Hypokalemic T waves fall and then rise above the cardiac resting membrane potential Wellens' Syndrome is a pattern of biphasic T waves in V2–3. It is generally present in patients with ischemic chest pain. Type 1: T-waves are symmetrically and deeply inverted Type 2: T-waves are biphasic with negative terminal deflection and positive initial deflection Flattened T wave T wave is considered flat when the wave varies from -1.0 mm to + 1.0 mm in height. Hypokalemia or digitalis therapy can cause flattened T wave with a prominent U wave. As hypokalemia progressively worsens, T wave becomes more flatten while U wave becomes more prominent, with progressively deeper ST segment depression. For digitalis toxicity, there will be sagging QT interval, flattened T wave, and prominent U wave with a shortened QT interval. Hyperacute T wave These T waves may be seen in patients displaying Prinzmetal angina. Additionally, patients exhibiting the early stages of STEMI may display these broad and disproportional waves. 'Camel hump' T wave The name of these T waves suggests the shape it exhibits (double peaks). Since these T wave abnormalities may arise from different events, i.e. hypothermia and severe brain damage, they have been deemed as nonspecific, making them much more difficult to interpret. Peaked T wave High blood potassium levels (hyperkalemia) can cause "peaked t-waves." See also Electrocardiography (ECG) Cardiac action potential QRS Complex P wave Cardiac pacemaker References Cardiac electrophysiology