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Case presentation: A male newborn was diagnosed with severe hypertrophic cardiomyopathy (HCM) because of a heart murmur. A genetic test identified the previously described pathogenic variant Arg719Trp in MHY7, which was not present in the parents. An additional variant in KCNE2, Ile57Thr, considered as a risk factor for acquired long QT, was found in the patient. Corrected QT interval was normal. At age 3, the child suffered cardiac arrest from which he was successfully defibrillated. Maximal wall thickness was 20 mm (z-score +18). With the patient weighing 18 kg, a subcutaneous implantable cardioverter defibrillator (s-ICD) was implanted with the two-incision technique and nadolol 2 mg/kg/day was started. After 3 appropriate ICD therapies in the following 3 months, amiodarone was associated to betablockers, with no QT prolongation. He suffered 8 more ventricular fibrillation-terminating ICD shocks in the following year, prompting the indication of thoracoscopic bilateral cardiac sympathectomy denervation (BCSD) and referring him for heart transplant evaluation. Following BCSD he was symptom free for 6 months, after which he presented with a prolonged cardiac arrest, needing sedation, 4 ICD shocks and external defibrillation to recover consciousness. After experiencing another electrical storm in the following month, he underwent successful cardiac transplantation at age 5. Discussion: This clinical case is noteworthy for different reasons. First of all, even if Arg719Trp mutation in MHY7 has been associated with full penetrance and early expressivity of HCM (mean age at diagnosis 24 years), the child presented with an extremely rare early-onset of recurrent fatal arrhythmias. The pathogenicity of the associated KNCE2 variant, Ile57Thr, has not yet been elucidated but it has been suggested to confer proarrhythmic susceptibility in the presence of other environmental or genetic risk factors. Another worth-mentioning clinical aspect is that s-ICD proved to be a safe and effective therapy in a child weighing much less than 30 kg. In this case in which heart transplant could not be avoided due to life-threatening arrhythmias, the benefit of the preservation of the central venous circulation with the absence of intravascular leads cannot be overstated.

Introduction: Children and adolescents treated with anthracyclines are at increased risk of developing cardiomyopathy. Although several guidelines are available, no consensus exists on an optimal strategy scheme for predict or avoid anthracycline-induced cardiotoxicity. Methods: Cardiotoxicity was defined as a reduction in left ventricle ejection fraction >10% from baseline and <53%, and/or global longitudinal strain drop of >15%.The incidence of cardiotoxicity, its relation with cumulative anthracycline doses, clinical significance and reversibility were retrospectively evaluated in a paediatric population (0-18 years) treated with anthracycline at a tertiary hospital (2010-2020). Analysis of 3 genetic polymorphisms related to cardiotoxicity (RARG (rs2229774), SLC28A3(rs7853758) and UGT1A6(rs17863783)) was performed. Results: A total of 84 patients (45 males) were included. The mean age at diagnosis was 10.7± 3.8 years with average cumulative anthracycline dose 195 mg/m2 (60-460mg/m2). Median follow-up was 5 years. Anthracycline-induced cardiotoxicity occurred in 12 (14,2%) of treated patients, 75% were asymptomatic. 5 patients experimented acute cardiotoxicity during treatment. 8 patients were treated with ACE-inhibitors and/or beta-blockers. 11 patients had full function recovery. Cumulative doxorubicin dose was a risk factor of cardiotoxicity, being affected 9/20 treated with >250 mg/m2; 3/51 treated with 100-250m2; while no patient out of 13 receiving <100 mg/m2 had an abnormal echocardiogram (P <0.01). A higher percentage of patients treated with mediastinum radiation and chemotherapy (3/7:42%) presented cardiotoxicity compared to those with chemotherapy only (9/77:9%) (p0.09). Younger age, female sex or the presence of genetic polymorphisms studied were not statistically significant risk factors. Conclusions: Dose-dependent anthracycline risk for developing cardiomyopathy was confirmed. However, previously identified risk factors including female sex, early age at diagnosis and genetic polymorphism were not replicated in this population, possibly due to the small sample size and the relatively short follow-up period. A tailored monitoring strategy based on cardiac risk stratification is needed.

Background and aims Critical congenital heart diseases (CCHD) can be missed by prenatal ultrasound and physical examination (30%newborns unrecognised CCHD). This fact entails risk of cardiogenic shock, neurological damage and death. The American Paediatric Association supports the universal screening of CCHD by pulseoximetry. This study aimed to evaluate the rate of unrecognised CCHD in newborn before the universal pulseoximetry was stablished in Spanish third level hospital. To describe the initial results after its implantation. Methods 1) Retrospective review, showing the incidence of CCHD and late detection rate before pulseoximetry screening implantation. 2) Prospective analyse, after its recent introduction. Were assessed pulseoximetry preductal and postductal before hospital discharge. Screen was considered abnormal: 1) Oxygen saturation <90%, 2) Oxygen saturation <95% in both extremities on 3 measures,(3) >3% difference oxigen saturation between right hand and foot. Results Incidence CCHD in 18 months before pulseoximetry was 1,8:1000. There were 10 CCHD diagnosed out of 5500 newborn: 3(30%) prenatally, 4(40%) by physical examination before discharge and 3(30%) after hospital discharge. Since pulseoximetry screening (May 2013), there have been 4 patients (out of 3068 deliveries) with CCHD, all of them diagnosed before hospital discharge (2 prenatally, 2 by physical examination and pulseoximetry). There were 2 false positives (0,06%), one of them was diagnosed of situs inversus totalis, probably related to Kartagener syndrome. Conclusion Conventional screening for congenital heart disease can lead to a significant rate of unrecognised CCHD. Pulseoximetry may be a useful screening test, false-positive rate was particularly low (<0,1%). More studies are needed to assess its long-term real value and economic impact in our heath system.