Heterogeneity of ventricular repolarization in newborns with intrauterine growth restriction

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BackgroundIntrauterine growth restriction (IUGR) is associated with structural and functional cardiac alterations but the electrophysiological consequences of these disturbances remain unknown. AimsTo explore the distribution of ventricular repolarization and its relation to myocardial mechanics in newborns with IUGR. Study design, subjects and outcome measurementsConventional and tissue Doppler echocardiographic data, and electrocardiographic parameters used to describe the distribution of ventricular repolarization (dispersion of QT [QTd] and JT [JTd]), were obtained on the second (D2) and fifth (D5) postnatal day and compared between 25 IUGR newborns and 25 matched-for-gestational age controls. ResultsIUGR was associated with relative interventricular septum hypertrophy, increased left ventricular (LV) E/E′ ratio and higher LV myocardial performance index (MPI). On both study days, the IUGR infants presented higher QTd and JTd compared to controls (QTd-D2: 66±20ms vs. 36±12ms, P<0.001; JTd-D2: 54±13ms vs. 34±9ms, P<0.001; QTd-D5: 61±14ms vs. 27±12ms, P<0.001; JTd-D5: 54±13ms vs. 27±9ms, P<0.001). The association between QTd and LV E/E′ (D2: regression coefficient beta 0.747, R2 0.585; D5: beta 0.843, R2 0.646) and QTd and MPI (D2: beta 0.680, R2 0.576; D5: beta 0.698, R2 0.650) was also significant (P<0.001 for all analyses). ConclusionsOur findings suggest that IUGR is associated with electrophysiological remodeling of the neonatal heart, a process which is closely related to the underlying alterations in ventricular mechanics and might predispose to adverse electrophysiological events.