T-wave is a waveform that is routinely present on the ECG, and under normal circumstances, most of them are in the same direction as the main QRS wave. Common causes of t-wave inversion may include myocardial ischemia, myocardial disease itself, hypokalemia, etc. 1. Myocardial ischemia: coronary artery is a group of arteries supplying blood to the myocardium, if there is coronary atherosclerosis or coronary artery spasm, the blood vessels will become narrowed, which will lead to a decline in blood supply to the myocardium, resulting in myocardial ischemia causing t-wave inversion. 2. Myocardial disease itself: myocardial disease itself may also be T wave inversion, common myocarditis, hypertrophic obstructive cardiomyopathy, dilated cardiomyopathy and so on. 3. Hypokalemia: usually caused by diarrhea, diuretic use, serum potassium below 3.5mmol/L is considered as hypokalemia. The ECG will also show t-wave inversion. It is suggested that patients should not diagnose on their own, but should go to regular hospitals, complete the relevant examinations and follow the doctor’s instructions for treatment.