Left ventricular non compaction (LVNC) is a rare cause of cardiomyopathy related to abnormal in utero myocardial development, leading to prominent trabeculations. Its prognosis remains unclear with conflicting data and mortality ranging from 2 to 38%.

The aim of this study was to define the prognosis of newly diagnosed LVNC as compared to recently diagnosed dilated cardiomyopathy (DCM).

A prospective multicentric study with a 2-year follow-up was designed. The primary endpoint combined cardiovascular death, heart transplantation and hospitalisation for cardiovascular events. Three groups of patients were defined: Group A: new cases of LVNC, Group B: new cases of DCM, Group C: 1st degree LVNCs’ relatives identified as affected with LVNC. Post Hoc analysis were designed according to the 2019 DCM definition and 3 LVEF-matched subgroups were described: Group 1: LVNC with LVEF<45%, Group 2: LVNC with LVEF>45%, Group 3: DCM with LVEF<45%.

94 LVNC and 67 DCM were included, with significant difference on LVEF, (43.4% vs 35.7%, P=0.001). The post hoc analysis of the LVEF-matched subgroups showed a tendency to more frequent primary endpoint occurrence in LVNC as compared with DCM (N=20 [35.7%], vs. N=10; [19.6%], respectively, P=0.075). In the LVNC population, 28.5% of rhythmic complications, 17.8% of haemodynamic complications and 3.5% of thromboembolism were observed. We also observed a higher number of cardiovascular events by patient in LVNC as compared with DCM patients (20.7% vs. 8.5%, P=0.087).

We report the first prospective study comparing LVNC to DCM showing a tendency to an excess morbidity-mortality in the LVNC population. Our results allow to improve patient care as rhythmic disorders appear as the main complication, followed by heart failure and thromboembolism.