Background: Left ventricular noncompaction (LVNC) is a distinct cardiomyopathy characterized by the presence of a two-layer myocardium with prominent trabeculation and deep intertrabecular recesses. The diagnosis of LVNC can be challenging because the diagnostic criteria are not uniform. The aim of our study was to evaluate echocardiographic and CMR findings in a group of children with isolated LVNC. Methods: From February 2008 to July 2021, pediatric patients under 18 years of age at the time of diagnosis with echocardiographic evidence of isolated LVNC were prospectively enrolled. The patients underwent echocardiography and contrast-enhanced cardiovascular magnetic resonance (CMR) with late gadolinium enhancement to assess myocardial noncompaction, ventricular size, and function. Results: A total of 34 patients with a median age of 11.9 years were recruited. Patients were followed prospectively for a median of 5.1 years. Of the 31 patients who met Jenni’s criteria in echocardiography, CMR was performed in 27 (79%). Further comprehensive analysis was performed in the group of 25 patients who met the echocardiographic and CMR criteria for LVNC. In echocardiography, the median NC/C ratio in systole was 2.60 and in diastole 3.40. In 25 out of 27 children (93%), LVNC was confirmed by CMR according to Petersen’s criteria, with a median NC/C ratio of 3.27. Conclusions: 1) Echocardiography precisely identifies patients with LVNC. 2) Echocardiography is a good method for monitoring LV systolic function, but CMR is indicated for the precise assessment of LV remodeling and RV size and function as well as for the detection of myocardial fibrosis.

Background: Left ventricular noncompaction (LVNC) is a genetically and phenotypically heterogeneous cardiomyopathy characterized by a two-layered myocardium consisting of compacted and noncompacted segments, prominent ventricular trabeculations, and intertrabecular recesses. Patients with LVNC are at increased risk to develop heart failure, atrial and ventricular arrhythmias, and/or systemic thromboembolic events. Familial forms of primary sinus bradycardia have been attributed to mutations in HCN4. There are very few reports about the association between HCN4 mutations and LVNC. The aim of our study was to characterize the clinical phenotype of families with LVNC and sinus bradycardia caused by mutation of the HCN4 gene. Methods: From March 2008 to July 2021 we prospectively enrolled 6 patients from 4 families with diagnosed isolated LVNC based on the clinical presentation, family history and echocardiographic and cardiovascular magnetic resonance (CMR) evidence of LVNC. Next generation sequencing (NGS) analysis was undertaken for evaluation of the molecular basis of the disease in each family. Results: A total of 6 children (median age 11 years) were enrolled and followed prospectively for the median of 12 years. All 6 patients were diagnosed with LVNC by echocardiography and 5 participants additionally by CMR. The presence of LGE was found in 3 children. Sinus bradycardia and dilation of the ascending aorta occurred in 5 studied patients. In 4 patients from 3 families the molecular studies demonstrated the presence of rare heterozygous HCN4 mutations. Conclusion: (1) The HCN4 mutation influences the presence of a complex LVNC phenotype, sinus bradycardia and dilation of the ascending aorta. (2) HCN4 mutation may be associated with the early presentation of clinical symptoms and the severe course of the disease. (3) It is particularly important to assess myocardial fibrosis not only within the ventricles, but also in the atria in patients with LVNC and sinus bradycardia.