calculated heart weight heart weight to body weight ratio A calculated value in which the weight of the heart, the chambered, muscular organ in vertebrates that pumps blood received from the veins into the arteries, thereby maintaining the flow of blood through the entire circulatory system, is divided by the total weight of the body, and the result presented as a ratio, fraction, quotient or percentage, thus normalizing it to body weight and, by extension, to the size of the organism.