Brief Communication Anomalous Cardiovascular Structures in a Guinea Pig

A pregnant guinea pig, anesthetized and intubated for an experimental procedure, was found to have cardiovascular anomalies. An apparent caudal vena cava had a normal course from the diaphragm and the heart. A second vena cava, however, accompanied the aorta from the diaphragm to the heart. The anatomical vena cava got blood from the gastrointestinal circulation while blood flowed into the aberrant vena cava from the adrenal glands, kidneys, ovaries, uterus, and hind limbs. The two caudal venae cavae, the cranial vena cava and the pulmonary veins emptied into a large sac-like structure on the base of the heart instead of atria. The pulmonary artery and the aorta originated from the ventricles. The left and right auricular appendages were in correct relationship to the respective ven-tricles. The translucent sac had normal atrial myocardial cells (as determined by light microscopy) and the entire heart was slightly enlarged and flaccid. There were no atrioventricular valves and there was a ventricular septal defect in the basal third of the septum