Experimental Mitral Stenosis and Ascites Formation

Extreme care must be taken in the production of experimental mitral stenosis in dogs by the method of controlled progressive constriction of the mitral ring in order to prevent the inadvertent constriction of the thoracic inferior vena cava and resultant elevation of the inferior caval pressure. After a report from Hamilton, Ellison, Hague and Brown (Georgia Laboratories) that ascites formation was a common occurrence in dogs with experimental mitral stenosis produced by this technique, an attempt was made by Davis and Howell (Bethesda workers) to repeat these observations. From experiments performed in Bethesda, it was found that a stricture of the thoracic inferior vena cava was produced when the Georgia technique for production of mitral stenosis was used; this constriction provided an explanation for the ascites formation. These results were communicated to the Georgia workers who explored the two surviving dogs of their first series and found evidence which suggested that the inferior vena cava was patent even though the dogs were producing ascites profusely. Later, the Georgia group produced mitral stenosis in two additional dogs by the original technique and these animals gave unequivocal evidence that the stricture was present. Great care was then taken by the Georgia workers in placing the constricting ligature to avoid stricture of the orifice of the inferior vena cava. Of the 13 dogs so treated only 1 produced ascites and it had a small obstruction in the inferior vena cava. These last experiments by the Georgia workers as well as those of the Bethesda group suggest that ascites does not occur secondary to experimental mitral stenosis in dogs.