Dimensional changes of the left ventricle during acute pulmonary arterial hypertension in dogs

Left ventricular dimensions and volumes were measured by an endocardial marker technique in eight closed chest dogs during progressive increases of 10 mm Hg in mean pulmonary arterial pressure. Right ventricular volumes were measured by biplane cineanglography. Increasing mean pulmonary arterial pressure caused a progressive increase in right ventricular volume; at a mean pulmonary arterial pressure of 60 mm Hg, right ventricular end-diastolic volume increased by 48 percent and end-systolic volume by 50 percent. Left ventricular volumes began to decrease significantly at a mean pulmonary arterial pressure of 30 mm Hg, and when a mean pulmonary arterial pressure of 60 mm Hg was reached, left ventricular end-diastolic volume had decreased by 30 percent and left ventricular end-systolic volume by 19 percent. Changes in ventricular filling pressure dlrectionally followed the volume changes of the respective ventricle. Left ventricular stroke volume decreased 45 percent at a mean pulmonary arterial pressure of 60 mm Hg but increasing heart rate prevented a decrease in cardiac output. The decrease in left ventricular volume as pulmonary arterial pressure was Increased was associated with a disproportionate reduction in the left ventricular septal-lateral axis. At end-diastole, this dimension decreased by 22 percent at a mean pulmonary arterial pressure of 60 mm Hg, the anterior-posterior axis decreased by 8 percent and the base-apex axis by 4 percent. A similar disproportionate decrease of the septal-lateral axis occurred at end-systole. Even at the modest increase in mean pulmonary arterial pressure to 20 mm Hg, only the septal-lateral dimension was significantly shortened, and the right ventricular end-diastolic volume had increased by 17 percent but left ventricular end-diastolic volume was not significantly changed. Thus, during acute pulmonary hypertension, the right ventricle progressively dilates resulting in a distinctive change in the shape of the left ventricle that suggests septal buiging and that may impair left ventricular function.