A boy, aged 13, suffers from an abrupt aggravation of condition, there appeared shortness of breath, skin paleness with cyanosis. BP - 80/55 mm Hg, Ps- 128/min, heart sounds weakened. On ECG: diffuse muscular changes, polytopic extrasystole. Radiologically: acute enlargement of the heart borders in all directions. Two weeks ago there occurred a reaction on analgin administration. What is the most likely diagnosis?