While recоvering frоm а cоronаry stent procedure, а 52-year-old man complained of difficulty breathing. The physical examination revealed tachycardia and tachypnea, and his limbs were cold and clammy. The examiner also noted distended neck veins, diminished heart sounds, and a pericardial friction rub. Two-dimensional echocardiography showed pericardial effusion and ventricular compression. A serious condition in which a large amount of fluid accumulates in the pericardial cavity and puts pressure of the heart is