Low T-wave in sinus rhythm may be caused by myocardial ischemia, cardiomyopathy such as dilated cardiomyopathy, hypertrophic cardiomyopathy, hypokalemia, etc. Sinus rhythm is a normal heart rhythm from the sinus node. Sinus rhythm is the rhythm from the sinus node, which is a normal heart rhythm. low T-wave refers to a kind of T-wave change in the electrocardiogram, which suggests that myocardial ischemia may occur; for some myocardial pathologies, such as dilated cardiomyopathy, hypertrophic cardiomyopathy, etc., which can also cause T-wave flattening; hypokalemia can also cause T-wave flattening. T-wave hypoplasia can also occur in normal people, but it is physiologic and does not cause any symptoms. When T-wave hypoplasia occurs, it is important to combine the clinical history and symptoms to make an accurate judgment.