Counterclockwise rotation of the heart is a concept within the ECG and the standard term is anticlockwise rotation. The normal range of variation in the cardiac axis is large, between -30° and 110° usually between 0° and 90°. It is generally considered that 0° to 30° is mild leftward deviation, -30° to -45° is moderate leftward deviation, and -45° to -90° is severe leftward deviation. Mild anticlockwise transposition has no clinical significance. Significant anticlockwise transposition often indicates left ventricular hypertrophy, mostly in patients with hypertensive disease. Physiological factors such as obesity, pregnancy, ascites, etc. can cause left-axis deviation, and pathological factors such as hypertension, heart disease, hypertrophic cardiomyopathy, etc. can also cause left-axis deviation.