Longitudinal myocardial contribution to peak systolic flow and stroke volume in the neonatal heart

Abstract

Systolic longitudinal myocardial function is important for cardiac ejection. Data describing hemodynamic determinants and the time course of myocardial longitudinal contraction as measured by tissue Doppler are lacking. Ten newborn pigs were used for invasive hemodynamic investigation. Tissue Doppler assessment of the lateral part of the mitral valve annulus during systole was performed during pharmacological modulation of inotropy, cardiac pacing, and modulations of loading conditions. The strongest association was found between peak systolic velocity (S′) and peak systolic flow (PSF) and end-systolic pressure (ESP), respectively (β = 0.09 cm/mL, p < 0.001 and β =-0.07 cm/mL, p = 0.003). Displacement (D) was mostly influenced by stroke volume (SV) (β = 0.05 cm/mL, p < 0.001). Ejection time, SV, ESP, maximum first derivative of pressure (dP/dtmax), and PSF were all associated with S′ and D under different states of hemodynamic modulation; however, the ratio between PSF and S′, SV, and D were stable during hemodynamic modulations. Normalized cross correlations indicate that S′ and D follow the same trajectory as flow and SV, respectively. In conclusion, this study provides validity of accounting systolic D in the long axis as the longitudinal contribution to SV and peak systolic tissue velocity as the longitudinal contribution to PSF. Copyright © 2011 International Pediatric Research Foundation, Inc.