LMCA has several meanings in medicine, it can refer to the left main coronary artery (left-main-coronary-artery) or the left middle cerebral artery (left-middle-cerebral-artery), which needs to be determined in context. The left main coronary artery is the proximal segment of the left coronary artery, originating from the left coronary sinus and bifurcating at the end to give off the left anterior descending and left circumflex branches. The left main coronary artery can be divided into sinusoidal, intermediate, and distal segments, and mainly supplies about 75% of the left ventricular myocardium; therefore, severe lesions of the left main coronary artery will result in fatal left heart insufficiency and arrhythmias. The left middle cerebral artery is the direct continuation of the internal carotid artery, with a diameter of about 4 mm, which can be divided into five segments according to its travel, and the branches of the left middle cerebral artery are divided into two groups: the central branch and the cortical branch. If the left main coronary artery or middle cerebral artery is diseased, go to the hospital in a timely manner to clarify the cause of the disease and follow the doctor’s instructions for treatment.