Background:Left ventricular noncompaction (LVNC) is morphologically characterized by numerous prominent trabeculations and a severely thickened, two-layered myocardium. The fetal onset of LVNC has rarely been described.

Methods and Results:We conducted nationwide retrospective surveys on fetal cardiomyopathy (CM) in Japan from 2010 to 2016, from which 38 fetal patients with CM were enrolled, including 16 patients with LVNC. The rate of diagnostic concordance was 56.3% between fetal and postnatal visits in LVNC patients. The increase in the ratio of noncompacted to compacted (N/C) myocardium was time-dependent throughout the fetal period till birth (LV lateral: 1.6±0.1 to 2.8±0.2; LV apex: 2.0±0.1 to 3.2±0.2). Of all fetuses, 16 (42.1%) died or underwent heart transplantation (HT), with 3 intrauterine deaths. Lower fetal cardiovascular profile score (odds ratio, 26.9; P=0.0266) was a risk factor for death or HT. N/C ratio ≥1.6 at the apex at the first visit was a significant predictor of LVNC (odds ratio, 47.8; P=0.0113).

Conclusions:This is the first study to reveal the etiology of fetal CM based on results from a nationwide survey in Japan, highlighting the difficulty of diagnosing LVNC in fetal patients. To better understand and manage fetal CM, novel diagnostic criteria of LVNC in fetus should be established.

背景：左心室致密化不全（LVNC）在形态学上以许多突出的小梁和严重增厚的两层心肌为特征。很少描述 LVNC 的胎儿发病。

方法与结果：我们于2010年至2016年对日本全国范围内的胎儿心肌病（CM）进行回顾性调查，共纳入38例胎儿CM患者，其中LVNC患者16例。LVNC 患者的胎儿和产后就诊之间的诊断一致性率为 56.3%。非致密心肌与致密 (N/C) 心肌比率的增加在整个胎儿期直至出生时呈时间依赖性（LV 外侧：1.6±0.1 至 2.8±0.2；LV 心尖：2.0±0.1 至 3.2±0.2）。在所有胎儿中，16 名 (42.1%) 死亡或接受了心脏移植 (HT)，其中 3 名宫内死亡。较低的胎儿心血管特征评分（优势比，26.9；P=0.0266）是死亡或 HT 的危险因素。第一次就诊时心尖处的 N/C 比 ≥1.6 是 LVNC 的重要预测因子（优势比，47.8；P=0.0113）。

结论：这是第一项基于日本全国调查结果揭示胎儿 CM 病因的研究，突出了胎儿患者 LVNC 诊断的难度。为了更好地了解和管理胎儿 CM，应建立新的胎儿 LVNC 诊断标准。