Background: The causes of cardiomyopathy in children are less well described than in adults. We evaluated the clinical diagnoses and genetic causes of childhood cardiomyopathy and outcomes of cascade genetic testing in family members. Methods: We recruited children from a pediatric cardiology service or genetic heart diseases clinic. We performed Sanger, gene panel, exome or genome sequencing and classified variants for pathogenicity using American College of Molecular Genetics and Genomics guidelines. Results: Cardiomyopathy was diagnosed in 221 unrelated children aged ≤18 years. Children mostly had hypertrophic cardiomyopathy (n=98, 44%) or dilated cardiomyopathy (n=89, 40%). The highest genetic testing diagnostic yields were in restrictive cardiomyopathy (n=16, 80%) and hypertrophic cardiomyopathy (n=65, 66%), and lowest in dilated cardiomyopathy (n=26, 29%) and left ventricular noncompaction (n=3, 25%). Pathogenic variants were primarily found in genes encoding sarcomere proteins, with TNNT2 and TNNI3 variants associated with more severe clinical outcomes. Ten children (4.5%) had multiple pathogenic variants. Genetic test results prompted review of clinical diagnosis in 14 families with syndromic, mitochondrial or metabolic gene variants. Cascade genetic testing in 127 families confirmed 24 de novo variants, recessive inheritance in 8 families, and supported reclassification of 12 variants. Conclusions: Genetic testing of children with cardiomyopathy supports a precise clinical diagnosis, which may inform prognosis.

Congenital portosystemic shunts are often associated with systemic complications, the most challenging of which are liver nodules, pulmonary hypertension, endocrine abnormalities, and neurocognitive dysfunction. In the present paper, we offer expert clinical guidance on the management of liver nodules, pulmonary hypertension, and endocrine abnormalities, and we make recommendations regarding shunt closure and follow-up.

Background: Congenital portosystemic shunts (CPSS) are rare vascular anomalies resulting in communications between the portal venous system and the systemic venous circulation, affecting an estimated 30,000 to 50,000 live births. CPSS can present at any age as a multi-system disease of variable severity mimicking both common and rare pediatric conditions. Case presentations: Case A: A vascular malformation was identified in the liver of a 10-year-old girl with tall stature, advanced somatic maturation, insulin resistance with hyperinsulinemia, hyperandrogenemia and transient hematuria. Work-up also suggested elevated pulmonary pressures. Case B: A young girl with trisomy 8 mosaicism with a history of neonatal hypoglycemia, transient neonatal cholestasis and tall stature presented newly increased aminotransferase levels at 6 years of age. Case C: A 3-year-old boy with speech delay, tall stature and abdominal pain underwent abdominal ultrasound (US) showing multiple liver nodules, diagnosed as liver hemangiomas by hepatic magnetic resonance imaging (MRI). Management and outcome: After identification of a venous malformation on liver Doppler US, all three patients were referred to a specialized liver center for further work-up within 12 to 18 months from diagnosis. Angio-computed tomography (CT) scan confirmed the presence of either an intrahepatic or extrahepatic CPSS with multiples liver nodules. All three had a hyperintense signal in the globus pallidus on T1 weighted cerebral MRI. Right heart catheterization confirmed pulmonary hypertension in cases A and C. Shunts were closed either using an endovascular or surgical approach. Liver nodules were either surgically removed if there was a risk of malignant degeneration or closely monitored by serial imaging when benign. Conclusion: These cases illustrate most of the common chief complaints and manifestations of CPSS. Liver Doppler US is the key to diagnosis. Considering portosystemic shunts in the diagnostic work-up of a patient with unexplained endocrine, liver, gastro-intestinal, cardiovascular, hematological, renal or neurocognitive disorder is important as prompt referral to a specialized center may significantly impact patient outcome.

There is an incomplete understanding of the burden of splice-disrupting variants in definitively associated inherited heart disease genes and whether these genes can amplify from blood RNA to support functional confirmation of splicing outcomes. We performed burden testing of rare splice-disrupting variants in people with inherited heart disease and sudden unexplained death compared to 125,748 population controls. ClinGen definitively disease-associated inherited heart disease genes were amplified using RNA extracted from fresh blood, derived cardiomyocytes, and myectomy tissue. Variants were functionally assessed and classified for pathogenicity. We found 88 in silico-predicted splice-disrupting variants in 128 out of 1242 (10.3%) unrelated participants. There was an excess burden of splice-disrupting variants in PKP2 (5.9%), FLNC (2.7%), TTN (2.8%), MYBPC3 (8.2%) and MYH7 (1.3%), in distinct cardiomyopathy subtypes, and KCNQ1 (3.6%) in long QT syndrome. Blood RNA supported the amplification of 21 out of 31 definitive disease-associated inherited heart disease genes. Our functional studies confirmed altered splicing in six variants. Eleven variants of uncertain significance were reclassified as likely pathogenic based on functional studies and six were used for cascade genetic testing in 12 family members. Our study highlights that splice-disrupting variants are a significant cause of inherited heart disease, and that analysis of blood RNA confirms splicing outcomes and supports variant pathogenicity classification.

Portopulmonary hypertension is a rare but serious complication of portal hypertension or portosystemic shunting. Portopulmonary hypertension is an indication for liver transplantation or shunt closure. However, liver transplantation is contraindicated in patients with severe pulmonary arterial hypertension. Reported mortality rates are high in children with portopulmonary hypertension and there are scarce recommendations on its management. Our aim was to report on our real-world experience of managing portopulmonary hypertension in a specialised centre. We describe a series of 6 children with portopulmonary hypertension. Their median age at diagnosis was 13 years (range 10-15). The underlying liver conditions were cirrhosis of unknown origin (1), congenital portocaval shunts (3), biliary atresia (1), and portal vein cavernoma with surgical mesenterico-caval shunt (1). Median mean pulmonary arterial pressure was 47 mmHg (range 32-70), and median pulmonary vascular resistance was 6.6 Wood units (range 4.3-15.4). All patients except one were treated with a combination of pulmonary arterial hypertension-specific therapy (phosphodiesterase type 5 inhibitors and/or endothelin receptor antagonists and/or prostacyclin analogues). Three patients then benefited from shunt closure and the others underwent liver transplantation. Five patients showed improvement or stabilisation of pulmonary arterial hypertension with no deaths after a mean follow-up of 39 months. Based on our limited experience, early and aggressive treatment with a combination of pulmonary arterial hypertension-specific therapy significantly improves patients' haemodynamic profile and enables the performance of liver transplantation and shunt closure with satisfactory outcomes.

Congenital and acquired heart diseases can cause pulmonary hypertension (PH) in children, either by increasing pulmonary blood flow (PBF), left atrial pressure (LAp), and/or pulmonary vascular resistance (PVR). Pathophysiological process of pulmonary vascular disease (PVD) in different types of congenital heart diseases (CHDs) are reviewed hereafter. As with other types of PH, a rigorous diagnostic evaluation is mandatory to characterize the etiology of the PH, rule out other or additional causes of PH, and establish a risk profile. Cardiac catheterization remains the gold standard exam for PH diagnosis. Treatment of pulmonary arterial hypertension (PAH) associated with CHD (PAH-CHD) can then be started according to the recent guidelines recommendations, although most of the evidence is extrapolated from studies on other causes of PAH. PH in pediatric heart disease is often multifactorial, and sometimes unclassifiable, making the management of these patients complicated. The operability of patients with a prevalent left-to-right shunt and increase of PVR, the management of children with PH associated with left-sided heart disease, the challenges of pulmonary vascular disorders in children with univentricular heart physiology and the role of vasodilator therapy in failing Fontan patients are some of the hot topics discussed in this review.