Diagonal branches are branches of the left anterior descending branch of the coronary arteries. The coronary arteries are the main arteries supplying blood to the heart and are divided into two main branches, the left coronary artery and the right coronary artery, each of which is further subdivided into smaller branches. The left coronary artery starts from the left coronary sinus and divides into the anterior descending branch and the circumflex branch. The anterior descending branch can be further divided into the conus arteriosus, diagonal branch, anterior left ventricular branch, and anterior right ventricular branch, which are responsible for most of the blood supply to the left ventricle and interventricular septum of the heart. The diagonal branch, as the main branch of the anterior descending branch, is mainly responsible for the blood supply to the anterior wall of the left ventricle. Stenosis of the diagonal branch is also a common cause of myocardial infarction. In conclusion, if you feel unwell, it is recommended that you seek prompt medical attention and receive standardized diagnosis and treatment.