Hemodynamic alterations in dogs with shock induced by intravenous injection of heartworm extract

To elucidate one way of the shock mechanisms, the hemodynamic alterations w ere examined in 7 dogs with heartworm (HW) extract-induced shock. The first alteration observed after injection of HW extract was a decrease in right ventricular end-diastolic pressure (RVEDP). After that, left ventricular (L V) end-diastolic pressure, LV systolic pressure, and LV dp/dt fell signific antly, followed by a decrease in the cardiac output of all dogs to below th e detectable level (1.00 iota /min). Since RVEDP depends on blood flow into the right ventricle, the decrease in RVEDP means a reduction in venous ret urn. Therefore, this study showed that the first trigger of a decrease in b lood pressure in HW extract-induced shock is the reduction in venous return .