Aorto-caval fistula in the rat. An experimental model of heart volume overloading.

Abdominal aorto-caval fistula was experimentally induced in rats, and animals were sacrificed 5 days, 1 month, and 6 months later. Cardiac weight almost doubled the normal weight during the first month. Cell length increased to the same extent as the cell width, indicating harmonious growth. Increase in cell volume, as well as the amount of degenerative changes, were more pronounced in subendocardium than in midwall and subepicardium. Cytological features of active cellular growth was found not only in the early stages (5 days and 1 month) but also 6 months after the operation. This finding is consonant with proteosynthesis stimulation not only in the early period of constitution of hypertrophy but also in the later stages.