Changes in cardiac dynamics by opening an interventricular shunt in dogs.

Changes in right and left ventricular (RV, LV) dynamics caused by an interventricular shunt were examined in open-chest dogs. At a pulmonary to systemic blood flow ratio of 1.7 +/- 0.2 pulmonary flow increased by 53 +/- 13%, whereas aortic flow decreased by 9 +/- 2%. Shunt flow was continuous from the left to the right ventricle throughout the cardiac cycle, but 72 +/- 4% took place during the LV ejection phase. Peak systolic LV pressure declined by 6 +/- 3 mm Hg, LV end-diastolic segment length (SL) rose, and systolic shortening of the SL increased. Peak systolic RV pressure rose from 28 +/- 3 to 36 +/- 3 mm Hg and RV end-diastolic and end-systolic SL rose almost equally. Accordingly, RV systolic SL shortening did not rise despite the substantial augmentation in RV outflow. The transseptal end-diastolic pressure gradient did not rise, while the transseptal peak systolic gradient decreased when the shunt was opened. Similarly directed alterations were observed when the shunt was opened at different preloads and when the shunt flow was varied. Local work in the anterior wall of the right ventricle (calculated from the RV pressure SL loop) rose by 26 +/- 4%, whereas RV stroke work (product of mean systolic right ventricular pressure and pulmonary flow) rose by 57 +/- 12%; difference, P less than 0.05. LV stroke work and local work in anterior LV free wall rose in proportion when the shunt was opened.(ABSTRACT TRUNCATED AT 250 WORDS)