Abstract
Alternative methods to assess ventricular diastolic function in the fetus are proposed. Fetal myocardial hypertrophy in maternal diabetes was used as a model of decreased left ventricular compliance (LVC), and fetal respiratory movements as a model of increased LVC. Comparison of three groups of fetuses showed that, in 10 fetuses of diabetic mothers (FDM) with septal hypertrophy (SH), the mean excursion index of the septum primum (EISP) (ratio between the linear excursion of the flap valve and the left atrial diameter) was 0.36 +/- 0.09, in 8 FDM without SH it was 0.51 +/- 0.09 (P=0.001), and in the 8 normal control fetuses (NCF) it was 0.49 +/- 0.12 (P=0.003). In another study, 28 fetuses in apnea had a mean EISP of 0.39 +/- 0.05 which increased to 0.57 +/- 0.07 during respiration (P<0.001). These two studies showed that the mobility of the septum primum was reduced when LVC was decreased and was increased when LVC was enhanced. Mean pulmonary vein pulsatility was higher in 14 FDM (1.83 +/- 1.21) than in 26 NCF (1.02 +/- 0.31; P=0.02). In the same fetuses, mean left atrial shortening was decreased (0.40 +/- 0.11) in relation to NCF (0.51 +/- 0.09; P=0.011). These results suggest that FDM may have a higher preload than normal controls, probably as a result of increased myocardial mass and LV hypertrophy. Prenatal assessment of LV diastolic function by fetal echocardiography should include analysis of septum primum mobility, pulmonary vein pulsatility, and left atrial shortening.
Highlights
The fetal circulation has four major communications between the systemic and pulmonary pathway: the foramen ovale, the ductus arteriosus, the ductus venosus, and the placenta
Comparison of the three groups in the first study showed that EI was 0.36 ± 0.09 (0.30-0.43) in fetuses of diabetic mothers with septal hypertrophy, 0.51 ± 0.09 (0.390.59; P = 0.001) in fetuses of diabetic mothers without septal hypertrophy, and 0.49 ± 0.12 in control fetuses (0.44-0.59; P = 0.003; Figure 4)
In the model of fetal breathing movements, fetuses in apnea had a mean EI of the flap valve of 0.39 ± 0.05 (0.29-0.48), which increased to 0.57 ± 0.07 during respiration (0.45-0.69; P < 0.001)
Summary
The fetal circulation has four major communications between the systemic and pulmonary pathway: the foramen ovale, the ductus arteriosus, the ductus venosus, and the placenta. The saturated blood from the umbilical vein reaches the heart through a triphasic high velocity flow in the ductus venosus, which goes directly to the left heart across the oval fossa, stretching the septum primum towards the left atrial cavity in late diastole. Ventricular diastole is a very complex phenomenon whose main components are relaxation, compliance, myocardial rigidity, and elastic recoil [1]. Relaxation is an active process occurring with energy consumption in the early ventricular filling, when the myocardial fibers return to their original state after ventricular contraction [2,3,4]. Compliance is a passive process occurring during late ventricular filling and atrial contraction, and is related to fiber distensibility. Myocardial rigidity is the contrary of ventricular compliance [5] and elastic recoil is a continuing decrease in ventricular pressure in early diastole [3]
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