Ejection Time-Corrected Systolic Velocity Improves Accuracy in the Evaluation of Myocardial Dysfunction: A Study in Piglets

This study aimed to assess the effect of correcting for the impact of heart rate (HR) or ejection time (ET) on myocardial velocities in the long axis in piglets undergoing hypoxia. The ability to eject a higher volume at a fixed ET is a characteristic of contractility in the heart. Systolic velocity of the atrioventricular annulus displacement is directly related to volume changes of the ventricle. Both ET and systolic velocity may be measured in a single heartbeat. In 29 neonatal pigs, systolic velocity and ET were measured with tissue Doppler techniques in the mitral valve annulus, the tricuspid valve annulus, and the septum. All ejection time corrected velocities (S((ET)), mean ± SEM, cm/s) decreased significantly during hypoxia (S(mva(ET)) 15.5 ± 0.2 to 13.2 ± 0.3 (p < 0.001), S(septal(ET)) 9.9 ± 0.1 to 7.8 ± 0.2 (p < 0.001), S(tva(ET)) 12.1 ± 0.2 to 9.8 ± 0.3 (p < 0.001)). The magnitude of change from baseline to hypoxia was greater for ejection time corrected systolic velocities than for RR-interval corrected velocities (mean ± SEM, cm/s); ΔS(mva(ET)) 2.3 ± 2.0 vs. ΔS(mva(RR)) 1.6 ± 1.1 (p = 0.02), ΔS(septal(ET)) 2.1 ± 1.0 vs. ΔS(septal(RR)) 1.6 ± 1.0 (p < 0.01), ΔS(tva(ET)) 2.3 ± 1.1 vs. ΔS(tva(RR)) 1.8 ± 1.3 (p = 0.04). The receiver operator characteristic (ROC) showed superior performance of S((ET)) compared with uncorrected velocities. The decrease in S((ET)) during hypoxia was not influenced by important hemodynamic determinants. ET-corrected systolic velocity improves accuracy and decreases variability in the evaluation of systolic longitudinal function and contractility during global hypoxia in neonatal pigs compared with systolic velocity alone. It is robust toward hemodynamic changes. This novel method has the potential of becoming a useful tool in clinical practice.