Cardiac and pulmonary artery pressure pulses in experimental mitral stenosis

The response of pulmonary artery systolic and diastolic pressure to acute elevation of left atrial mean pressure has been explored in animals with an open chest. The elevation of pressure within the left atrium has been effected by the production of simulated mitral stenosis. Observations were made only in the presence of a well-maintained systemic pressure level and in the absence of observable myocardial ischemia. Under these conditions, pulmonary hypertension was uniformly observed throughout all levels of elevation of left atrial pressure. The individual responses of the pulmonary artery systolic and diastolic pressures have been detailed. The observation has been made that electrocardiographic evidence of severe myocardial hypoxia may develop in the absence of apparent mechanical constriction of the coronary circulation. In the presence of such myocardial hypoxia, decompensation of the right ventricle was observed and pulmonary hypertension was no longer maintained.