Placental Transfusion Effect on Hemodynamics of Premature Newborns

Infants are placed in supine position on a flat surface and heart is imaged from a low subcostal view. SVC flow is identified by angling the beam anteriorly until the flow into the right atrium from SVC is seen using color Doppler. SVC diameter will be seen from a high parasternal long axis (PLAX) view. The transducer will be placed as close to the midline as possible to acquire directly anteroposterior views of SVC. Maximum and minimum internal diameters will be measured off-line from a frozen 2D image showing the vessel walls at the point where SVC starts to open into the right atrium. Due to the variation in vessel diameter through the cardiac cycle, mean of the maximum and minimum diameter is used for flow calculation. The velocity time integral (VTI) will be calculated from the Doppler velocity tracings and averaged over 5 consecutive cardiac cycles. SVC flow will be calculated using the Kluckow and Evans method = (VTI × 3.14 × (mean SVC diameter2/4) × heart rate) / body weight.

The FS is obtained from M-mode tracings or 2D imaging in the PLAX view at the tips of the mitral valve leaflets or in the parasternal short-axis (PSAX) view at the level of the papillary muscles. The left ventricular M-mode tracing is obtained from the PLAX or PSAX view. The cursor in M-mode should be placed perpendicular to the interventricular septum and posterior wall at the level of the posterior mitral valve leaflet. Left ventricular end-diastolic dimension (LVEDD) and left ventricular end-systolic dimension (LVESD) will be measured, and the FS is calculated using the following equation: FS (%) = (LVEDD - LVESD / LVEDD) × 100

Left ventricular end-diastolic dimension (LVEDD) and left ventricular end-systolic dimension (LVESD) will be measured to calculate the ejection fraction. The EF is calculated using the following equation: EF (%) = (LVEDV - LVESV/ LVEDV)× 100

The pulse wave (PW) Doppler across mitral inflow is composed of two waves: an E wave representing early passive ventricular filling (preload dependent) and an A wave representing late diastolic active filling as a result of atrial contraction.

The mitral E/A ratio and velocity will be done for assessment of left ventricular diastolic function.

The echocardiographic assessment of the CO can be obtained by measuring cross-sectional area (CSA) of the left or RV outflow tract at the level of aortic or pulmonary annulus and by measuring the velocity time integral (VTI) at the level of aortic or pulmonary valve by pulsed wave Doppler, respectively. The CO is calculated by using the following equation: Cardiac Output (CO)=SV×HR= VTI× CSA× Heart Rate

The left-sided parasternal "ductal" view is the window to obtain a clear 2D image of the ductus arteriosus. The ultrasound probe is placed in a true sagittal plane to the left of the sternum with the marker pointing toward the head to obtain the ductal view. The PDA is visualized as a structure leaving the left side of the junction of the main pulmonary artery and the left pulmonary artery (LPA) toward the descending aorta. Color Doppler may be used to visualize the direction of transductal blood flow. The transdustal diameter will be measured in this view. Velocity and direction of the shunt during the cardiac cycle can be obtained by applying continuous wave.