Background: Primary heart tumors (PHTs) in the pediatric population are very rare and do not manifest any characteristic symptoms. Methods: A retrospective analysis of 61 cases was undertaken. Data from three centers for the years 2003–2018 were gathered. The tumors’ clinical course, location, number, hemodynamic, treatment, and follow-up were evaluated. Echocardiography was complemented with magnetic resonance imaging, computer tomography, and histopathological examination. Results: Out of 61 PHT diagnoses, 56 (91.8%) were circumstantial including all 16 (26.2%) prenatal tumors. The reasons for cardiological consultations were arrhythmia, syncopes, lowered physical performance, and murmurs. Only five patients (8.2%) were suspected of tumors based on previous symptoms of sclerosis tuberosa. Rhabdomyoma was the most frequently found PHT (60.7%). The tumors were predominantly located in the ventricles (49.1%) and intraventricular septum (14.9%) and tended to be single (70.5%). About 37.7% of patients suffered from coexistent multi-organ problems, two (3.28%) from congenital heart defects and one (1.64%) from Carney’s syndrome. Tumor resection was performed on 26 (42.7%) patients, of which 16 (61.5%) underwent total and 10 (38.5%) partial tumor resection. During the follow-up (mean 4.3 years), 54 patients (88.5%) have improved or were stable, while seven (11.5%) died. Conclusions: Primary pediatric heart tumors are diagnosed completely circumstantially, and the most common is rhabdomyoma, although arrhythmia may suggest fibroma. Diagnosis of a heart tumor in children is not synonymous with fatal prognosis, and most of them require only constant observation. Life-saving operation allows improvement, while the prognosis for malignant tumors in children is definitely unfavorable.

In our study population we did not demonstrate the usefulness of KS to predict IVIG resistance or the risk of the occurrence of coronary artery aneurysms. However, prolonged fever, late diagnosis, poorly symptomatic course of the disease, and a high platelet count at the time of the follow-up remain independent risk factors.

Isolated non-compaction of the ventricular myocardium (INVM), sometimes referred to as ‘spongy myocardium’, is a congenital and exceedingly rare cardiomyopathy. Isolated ventricular non-compaction occurs in the absence of other structural heart diseases and, hypothetically, it is due to the arrest of myocardial morphogenesis. Isolated non-compaction of the ventricular myocardium may manifest itself from infancy to young adulthood with a high mortality rate. Both sexes are affected. In our study, we present a case of INVM (left and right ventricles) in a 3-year-old girl, diagnosed by two-dimensional echocardiography. The anomaly presented as a restrictive cardiomyopathy. The girl was admitted to our hospital with heart failure, when she was 10 months old. She was treated with dopamine, digoxin, furosemide, spironolactone, and acenocoumarol and her condition improved. Presently, the girl remains asymptomatic and for 3 years of follow-up, her development has been almost normal. We here describe the genetic background of this disorder (based on a literature review).