Final answer:
The abbreviation for a narrowing of the aorta is Coarctation of the aorta, which is not listed among the answer choices provided. The options given refer to other cardiac-related terms.
Step-by-step explanation:
The abbreviation that refers to a narrowing of the aorta is Coarctation of the aorta. This condition is characterized by the aorta becoming constricted, which can impede blood flow from the heart to the rest of the body. It is not one of the options listed in the question, but based on the provided information, 'Coarctation of the aorta' would be the correct term. The other abbreviations refer to different heart defects or issues: CHD (Congenital Heart Defect), VSD (Ventricular Septal Defect), DVT (Deep Vein Thrombosis), LV (Left Ventricle), and AS (Aortic Stenosis which is also a narrowing of the aorta but is not specified in the options).