*3.2. Anatomopathological Evaluation*

Eight LVNC cases that fulfilled APE criteria were evaluated (Figure 1). All patients had been transplanted in final stages of heart failure. Only one patient presented LVNC associated with CHD (heart 6, coarctation of the aorta with severely dilated aortic root and severe aortic insufficiency), and another one presented concomitant ischemic heart disease.

In macroscopic examination, all of them presented a non-compacted layer with prominent myocardial trabeculations, adjacent to a thin compacted layer and prominent myocardial trabeculations. Thickness of both layers was quantified in macroscopy slides and confirmed in haematoxylin/eosin samples, where the measurements were performed. Cellular hypertrophy was evaluated in both layers, and also the presence of fibrosis (Table 4).


**Table 4.** Histopathological characteristics of hearts with LVNC diagnosis. NC, non-compaction; C, compaction; LV, left ventricle. Cellular hypertrophy: 0 = none; 1 = mild; 2 = moderate; 3 = severe.

Cardiomyocytes description deserved special attention. In all analysed cases, their nucleus were enlarged, hyperchromatic and presented irregular striking shapes (Figure 4). Nevertheless, no remarkable abnormal nucleoli were found. Chromatin was, in general soft and without much heterochromatin volume. Cardiomyocyte diameter was enlarged in some of the layers, especially in non-compacted area. In seven cases, neither inflammatory infiltrate, necrosis nor other signs of histological malignancy were found. However, necrosis was identified in one heart, fibrosis in 3 of them, and some areas of slight fat infiltration and some of myocardiosclerosis.

**Figure 4.** Microscopic haematoxylin/eosin samples (×40) from LVNC explanted hearts. Panel (**A**) myocyte cellular hypertrophy (delimited by arrows); (**B**) deformed nuclear cardiomyocyte shapes.

Two patients died after heart transplant, without genetic testing. Out of the six available patients for genetic testing, LP/P variants were found in four of them, a VUS in the fourth one, and only B/LB variants in the other one, with concomitant CHD (heart six, excluded for clinical study). The genetic yield of this small but severely affected cohort of isolated LVNC is 80%.
