Anamnesis of a 30-year-old patient includes closed thoracic injury. Lately the patient has been suffering from increasing dyspnea, sensation of heaviness in the right subcostal area, and heart rate disturbances. Objectively: acrocyanosis, bulging cervical veins, ascites, edema of the lower extremities. Heart auscultation reveals muffled heart sounds, additional III heart sound is detected. Provisional diagnosis of constrictive pericarditis was made. What diagnostic technique would NOT confirm the diagnosis?