Description

In the developing fetus and premature infants, the early phase of passive filling (E wave) is less than the late active phase (A wave) resulting in an E/A wave ratio of less than 1.0. This relates to developmental immaturity of the preterm myocardium, which leads to poor myocardial compliance and impaired diastolic performance therein limiting passive flow. This differs from pattern seen in the term neonate, child and young adult where the majority of trans-mitral flow occurs in the early phase such that the E/A ratio is greater than 1.0. In neonates with a hemodynamically significant PDA, an increase in early trans-mitral flow occurs secondary to increased left atrial pressure, resulting in a pseudo-normalization of the E/A ratio which may be greater than 1.0 resembling the pattern seen in more mature patients. In 2D the LA and LV will appear dilated due to the increased pulmonary venous return