Background and aims Tumour is rare form of the congenital heart diseases – 0.32% among children and teenagers. Actually specific gravity of prenatal diagnosis is 21%–27%. Tumours majority is diagnosed at the age till 1 year. Approximately 85% of all heart tumours are rhabdomyoma, fibroma and teratoma.

Methods Patient K. with giant volume formation located in apical and medial segments of ventricular septum is observed in our centre from the age 9 month, now he is 5 years old. There were used: B-mode, 3-D and 4-D modes, which let us estimate proportion of anatomic features, the severity of left and right ventricles deformation.

Results According to transthoracic echocardiography its size was 47 × 36 mm, now – 34 × 32 mm. Heart pumping function was estimated as satisfying (Cardiac Index on pulmonary artery was more than 5 l/min/m²). There was not any dysfunction of the cardiac valves. There was a tachycardia and extrasystoles on the electrocardiography and there were not signs of the intraventricular conductivity dysfunction. Clinical picture doesn’t match to the tumour’s volume, because it doesn’t disturb to blood flow on the level of atrioventricular valves and on the outflow tracts of ventricles, and there is no any intraventricular asequence. The patient is on dynamic monitoring.

Conclusions Echocardiography (including 3-D and 4-D modes) is a primary method of the cardiac tumour diagnostics, which lets us accurately estimate anatomic ratio and heart functions. This applies both to prenatal and postnatal periods.