LONG AND SHORT AXIS DIMENSIONS OF THE LEFT-VENTRICLE CHANGE IN OPPOSITE WAYS DURING RESPIRATION

Cardiac output and stroke volume are known to vary with respiration. W hile right ventricular stroke volume increases on inspiration, left ve ntricular stroke volume decreases. This is an echocardiographic study of the changes in left ventricular dimensions in 20 healthy subjects. Our results show that the decrease in left ventricular stroke volume o n inspiration is a net effect of a decrease in short axis shortening d ue to a decrease in diastolic diameter by 4.8% (P < 0.001) and an incr eased motion in the long axis direction expressed as an increase in mi tral ring motion by 5.5% (P < 0.001). The findings point to the import ance of the interventricular septum for the regulation of stroke volum e.