Fig. 4.

Assessment of left heart pressure loading. Transmitral LV filling in normal term infants is characterized by a predominance of early diastolic (“E”) filling, with limited late LV filling occurring during atrial contraction (“A”), resulting in an E:A ratio >1. a Healthy preterm infants without a PDA have intrinsically decreased LV diastolic function, relying more on late atrial filling, and E:A ratio <1. b and c Preterm infants with a large PDA have increased left atrial pressure which results in earlier mitral valve opening and drives early passive filling, resulting in shortened isovolumic relaxation time (<40 ms) and a “pseudonormalized” E:A ratio >1