Influence of venous injection sites on evolution of dilution curves in dogs

¹ Department of Medicine, Marquette University School of Medicine, Milwaukee, Wisconsin

The role of venous passage of indicator from different venous injection sites on the genesis of right heart and pulmonary artery dilution curves was examined. Right heart and pulmonary artery thermodilution curves were recorded after injection of cool dye into commonly used portals—superior vena caval, right atrial, and inferior vena caval—and the contour compared with the subsequent femoral artery dye dilution curve. With superior vena caval or right atrial injection, the contour and disappearance slopes of the pulmonary artery curve bore an extremely variable relationship to those of the femoral artery curve. In sharp contrast, inferior vena caval injection yielded pulmonary artery curves with disappearance slopes which were highly correlated with the femoral artery slope (r = .99). With inferior vena caval injection, considerable temporal dispersion and spatial dispersion of indicator is found at the right atrial level. With superior vena caval injection distribution mainly occurred beyond the right atrium and even beyond the pulmonary artery in eight out of ten animal studies. The geometry of the venous system may explain this difference. Inaccuracies in flow calculation from right heart dilution curves in dogs would seem to be minimized by inferior vena caval injection.