Reduced left ventricular compacta thickness: a novel echocardiographic criterion for non-compaction cardiomyopathy

Left ventricular noncompaction (LVNC) is characterized by a two-layered myocardium consisting of a noncompacted inner and a compacted outer layer. The ratio of the thicknesses of these two layers is a major diagnostic criterion, which is, however, often difficult to apply in clinical practice.

Transthoracic echocardiography was performed in 41 patients with LVNC, 41 patients with moderate or severe aortic valve stenosis (AVS), and 41 age-matched normal controls. The maximal systolic thicknesses of "noncompacta" and "compacta" were measured in standard short-axis views at the apical or midventricular level, in the segment with most prominent recesses (in patients with LVNC) or trabeculation (in patients with AVS and controls).

The mean maximal systolic thickness of noncompacta was 1.8 ± 0.4 cm in patients with LVNC compared with 0.2 ± 0.1 cm in controls and 0.6 ± 0.02 cm in patients with AVS (P < .0001). The mean maximal systolic thickness of compacta was lower in patients with LVNC (0.5 ± 0.1 cm) compared to controls (1.2 ± 0.2 cm; P < .0001) and patients with AVS (1.6 ± 0.06 cm; P < .0001). The maximal systolic thickness of compacta was ≤8.1 mm in patients with LVNC compared with >8.1 mm (P < .0001) in controls and >8.1 mm in patients with AVS (P < .0001). The ratio of the maximal systolic thickness of the indexed basal septum to that of the compacta was ≥0.64/m(2) in patients with LVNC compared to ≤0.62/m(2) in controls and ≤0.96/m(2) in patients with AVS.

Maximal systolic compacta thickness <8 mm is specific for LVNC and allows the differentiation of LVNC from normal hearts as well as those with myocardial thickening due to AVS. This observation may be particularly useful as an additional diagnostic criterion for preventing the overdiagnosis of LVNC.