The mid-lad refers to the mid-section of the anterior descending branch of the left coronary artery, one of the main trunks of the coronary arteries that supply blood to the heart. The coronary arteries are the arteries that supply blood to the heart. They originate in the aortic sinus at the root of the aorta, and are divided into left and right branches that travel over the surface of the heart. The left main coronary artery is a short trunk, abbreviated LM, which branches off from the aorta into the left anterior descending branch and the left circumflex branch, abbreviated LAD and LCX, respectively.The left anterior descending branch supplies blood to the anterior wall of the left ventricle and to the anterior two-thirds of the interventricular septum. The left anterior descending branch supplies the left ventricular anterior wall and the anterior 2/3 of the ventricular septum, while the left circumflex branch supplies the left ventricular lateral and posterior walls, and in the case of the left dominant type, the left ventricular inferior wall, posterior wall, and posterior third of the septum. The right coronary artery has only one trunk, the RCA, which supplies the right atrium and right ventricle, and in the right dominant form, the left ventricular inferior wall, posterior wall, and the posterior third of the interventricular septum. Therefore, the left anterior descending branch, the left circumflex branch and the right coronary artery are the three trunks of the coronary arteries, each of which is vital to the heart. If you experience any discomfort, seek medical attention and follow the doctor’s instructions.