Maturational changes in left ventricular contractile state.

It has been suggested from animal and human studies that age-related alterations in left ventricular contractility occur. However, there is little information about growth-related changes in left ventricular performance from preterm infants to older children. In 22 preterm infants, 23 fullterm infants, and 35 children, left ventricular contractility was evaluated by two-dimensional and M-mode echocardiography. The rate-corrected mean velocity of fiber shortening (mVcfc)-end-systolic wall stress (ESS) relation was used as an index of contractility. There were significant inverse linear correlations between ESS and mVcfc in the three groups (all P<0.01). The slopes and y-intercepts of the regression lines of mVcfc-ESS relation were both significantly greater in the premature infants (mVcfc=-0.0133 ESS+1.62) and neonates (mVcfc=-0.0107 ESS+1.55) than those in the children (mVcfc=-0.0047+1.29). However, there were no significant differences between the premature and fullterm infants. Thus, these findings suggest that the contractility and afterload sensitivity of the left ventricle in the premature infants may be similar to those in the fullterm infants. In addition, our serial study in the premature infants showed that the ESS increased significantly with growth while the mVcfc did not change, suggesting that the left ventricular performance in the premature infants during early life was preserved in the setting of a lower afterload.