Whether a left-sided cardiac axis is important depends on the etiology. Both physiological conditions and diseases can cause a left-sided cardiac axis. Left-axis deviation is a common term used in ECG findings and can be seen in physiological conditions as well as pathological conditions. For example, obesity and pregnancy can cause the heart to be in a transverse position, with the apex of the heart shifting to the left, thus driving the leftward shift of the electrical axis, which usually does not matter and requires no specific treatment. In addition, diseases such as left ventricular hypertrophy, left anterior branch block, and right ventricular infarction can also cause a leftward bias in the cardiac axis. Left ventricular hypertrophy may be due to hypertension or heart disease and requires treatment for the primary cause. Left bundle branch block, left anterior branch block, and right ventricular infarction are more serious and need to be treated as soon as possible. Patients with left-sided cardiac axis are recommended to undergo cardiac ultrasound examination. If there are no obvious symptoms, but only left-sided electrical axis, there is no need to worry and regular review can be done.