Factors influencing late right ventricular ejection.

Forward flow from the right ventricle into the pulmonary artery continues longer than contraction in the right ventricular free wall. The momentum of blood flow, contraction of other areas of the right ventricular free wall, and movement of the interventricular septum are possible mechanisms regulating late right ventricular ejection. In this study the changes in shortening in right ventricular free wall and in free wall to septum distance were measured using sonomicrometry. Right ventricular free wall shortening was studied in both outflow and inflow regions in hoop and apex to base axes. Pulmonary artery flow was simultaneously measured using an electromagnetic flowmeter. Right ventricular free wall in the hoop axis was motionless during late ejection. The inflow segment in the hoop axis stopped shortening before all other segments (p less than 0.01). Both outflow and inflow segments in the hoop axis lengthened after the end of shortening. Both shortening of the right ventricular free wall in the apex to base axis and decrease in free wall to septum distance were continued until the end of ejection (p less than 0.01). Compared with the right ventricular outflow segment, the inflow segment shortened for a longer duration. It is concluded that forward flow during late right ventricular ejection is associated with continued shortening of the free wall in the apex to base axis. However, the results of this study do not exclude the role of septal bulge into the right ventricle during late ejection.