Hemodynamic Alterations of Acute Pulmonary Thromboembolism

A method is described of producing pulmonary embolism in the dog by the use of various-sized autologous clots made radiopaque. This method of experimental pulmonary embolism results in dilatation of the large- to small-sized pulmonary arteries and a consistent hemodynamic response in the pulmonary circulation, characterized by a marked rise in pulmonary arteriolar resistance with increased pulmonary arterial pressure but persistently normal pulmonary venous and "capillary" pressures. Data are presented to support the concept that the pulmonary hemodynamic changes that result from an initial pulmonary thromboembolism are primarily the result of vasoconstriction of the small pulmonary arteries or arterioles, presumably by a reflex mechanism. Mechanical blockage of the pulmonary vascular bed is considered to be of importance in causing hemodynamic alterations only after massive or repeated pulmonary embolism. The increase in pulmonary arteriolar resistance that results from the vasomotor response to pulmonar...