Left ventricular trabecular layer operates at high ejection fraction: implications for pump function assessment in excessive trabeculation

ABSTRACT Aims Numerous diagnostic criteria for excessive trabeculation (ET), or so-called “noncompaction”, score the extent of the trabecular layer, yet whether the trabeculations themselves have a negative or positive impact on pump function is largely unknown. This study aimed to measure the ejection fraction (EF) of the trabecular layer and its impact on pump function assessment. Methods and results We retrospectively analyzed cardiac magnetic resonance (CMR) findings in patients with ET of the left ventricle (LV). The LV was labelled into four regions: compact wall, central cavity (CC), trabeculations, and intertrabecular recesses (IR). For each label we calculated the systolic fractional volume change (SFVC) in short-axis images (n=15) and systolic fractional area change (SFAC) in 4-chamber images (n=30), by dividing end-systolic to end-diastolic values. We measured the EF of IR, CC, and total cavity (TC). Three methods to calculate EF of the TC were compared: trabeculations included (per guidelines), IR excluded (Jacquier criterion), trabeculations contoured and excluded (contour-EF). The SFVC and SFAC of the compact wall were similar with SFVC and SFAC of trabeculations (both P>0.05). In contrast, the IR were more diminished in systole by comparison with the CC, having lower SFVC (39±17% vs. 56±16%, P<0.001) and SFAC (37±22% vs. 72±12%, P<0.001). EF of the IR was also greater than EF of the CC (61±17% vs. 44±16%, P<0.001). Excluding IR from the TC or including trabeculations underestimates the contour-EF (44±16% and 40±12%, respectively, vs. 51±16%; both P<0.001). Conclusions The trabecular layer has a high EF. Values of key prognostic indicators are better when this is accounted for. Graphical Abstract EF, ejection fraction; LVEF, left ventricular ejection fraction; SAX, short-axis; 4c, 4 chamber. *P<0001