A 25-year-old patient complains of having dull heart pain for the last 10 days, dyspnea on mild exertion, palpitations. The diasease developed 2 weeks ago after a respiratory infection. Objectively: acrocyanosis, AP- 90/75 mm Hg, Ps-96/min. Cardiac borders appear to be shifted to the left and right. Heart sounds are weak and have triple rhythm, there is systolic murmur at the apex. ECG showed sinus rhythm, complete left bundle branch block. What is the most likely diagnosis?