A comparison of ventricular weights and geometry in newborn, young, and adult mammals.

The weight of individual anatomic segments of the heart and calculated left ventricular chamber volumes have been studied in the hearts of 214 normal mammals of seven species (sheep, swine, dogs, cats, rabbits, guinea pigs, and rats). Comparisons have been made between newborn, young, and adult age groups. In addition, the heart weight-to-body weight ratio, percentage of right ventricular free wall weight in relation to left ventricular free wall weight (RVF/LVF), the relationship between calculated ventricular volume and weight and the left ventricular major minor axis ratios were examined in each age range. Heart weight (HW) in relation to body weight (BW) was greater in the newborn than adult in all species except the dog. HW/BW was twice as great in the adult dog as other species. In newborns RVF/LVF ranged from 55 percent in rats to 100 percent in puppies. Less species variation was present in adult hearts. Species with a more spherical adult LV configuration demonstrated a greater chamber mass-to-volume ratio. This may be attributable to greater wall tension.