Abstract
Consideration of changes in LV performance during respiration generally invokes changes in either preload or afterload. We evaluated the effects of acute changes in right and left heart loading on LV filling in 5 open chest dogs acutely instrumented with mitral and aortic flow probes (QM and QA). With respiration halted, we acutely obstructed the inferior vena cava, pulmonary artery, and the ascending and descending thoracic aorta. Both IVC and PA occlusion cause QM to fall within one beat with QA then falling. Thus the lung acts as a conduit between the right and left hearts, with less than 500 msec required for volume transfer. The rapid infusion of blood into the RA with the pericardium in place results in QM falling for 2 beats and then sharply increasing. Changes in QA follow QM. In each dog the diastolic changes (QM) precede systolic (QA) consistent with diastolic interdependence being more important than systolic interdependence. Acute cross clamping of the descending aorta causes an immediate fall in QA with QM following.
In conclusion: 1) Right sided events have an immediate effect on LV filling and must be accounted for in explaining any changes in the LV during respiration. A rapid increase in systemic venous return may paradoxically initially decrease LV filling. 2) Changes in LV afterload immediately influence QA with QM following.
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Robotham, J., Stuart, R., Borkon, A. et al. 130 EFFECTS OF RIGHT AND LEFT HEART LOADING ON LV FILLING. Pediatr Res 19, 132 (1985). https://doi.org/10.1203/00006450-198504000-00160
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DOI: https://doi.org/10.1203/00006450-198504000-00160