The assessment of diastolic function in the developing fetus is difficult because of constantly changing conditions of loading. Previous reports suggesting improved ventricular compliance with fetal development are limited by the Doppler indices utilized. Using load-dependent and independent variables, we examined and compared serially right and left ventricular diastolic function in 11 normal fetuses (44 echocardiographic studies) at 22±1.0 weeks; 30±1.0 weeks; 36±1.0 weeks of gestation and 64±25 hours postnatally. Load-dependent indices included early to late time velocity integral ratios and percentage of early filling to total diastolic filling. The load-independent index was the peak filling rate normalized to the total time velocity integral. Both right and left ventricular time velocity integral ratios were similar initially, and shifted from late to early diastole with increasing gestational age (greater ratios). The shift in left ventricular ratios was greater, and increased earlier in fetal development. The right ventricular normalized peak filling rate decreased with increasing gestational age, while the left ventricular normalized peak filling rate remained constant, but was greater than the right ventricular rate postnatally. Both right and left ventricular filling shifts from late "active" to early "passive" diastole during fetal development. Left ventricular ratios are greater and increase earlier in fetal development, likely influenced by changes in preload. The right and left ventricular normalized peak filling rates were similar prenatally, indicating similar diastolic filling properties, but disparate postnatally, consistent with improved left ventricular relaxation immediately preceding or at the time of onset of transitional circulation.
All Science Journal Classification (ASJC) codes
- Pediatrics, Perinatology, and Child Health
- Cardiology and Cardiovascular Medicine