Ventricular interaction during experimental acute pulmonary embolism

Although stroke volume may decrease markedly after acute pulmonary embolism, left ventricular end-diastolic pressure (LVEDP) usually changes very little, which suggests that compliance or contractility or both are reduced. To test the hypothesis that the altered LV function during pulmonary embolism is primarily due to reduced preload mediated by increased pericardial constraint, hemodynamics and chamber dimensions (measured by sonomicrometry) were assessed in seven anesthetized dogs during control volume loading, after pulmonary embolism (with autologous blood clot), and after repeated pulmonary embolism in the volume-loaded state. The correlation between LVEDP and an index of LVED volume (LVED area index) throughout a wide range of LVEDP before and after embolism was poor (mean r = 0.42; range, 0-0.82). However, the correlation between transmural LVEDP (LVEDP-directly measured pericardial pressure) and LVED area index (mean r = 0.78; range, 0.61-0.94) was significantly higher (p = 0.03). Similarly, an index of stroke work (LV area stroke work) correlated less well (p less than 0.01) with LVEDP (mean r = 0.43; range, 0.07-0.77) than with transmural LVEDP (mean r = 0.82; range, 0.68-0.92). LV area stroke work also correlated well with the LV area index (mean r = 0.84; range, 0.70-0.95). These data indicate that neither compliance nor contractility is substantially altered during acute pulmonary embolism. The altered LV performance is due to reduced LV preload as reflected by a decrease in transmural LVEDP. This study also demonstrates that LVEDP is a poor index of LV preload during pulmonary embolism, whereas transmural LVEDP accurately reflects LVED dimensions.