The most likely diagnosis in this patient is effusive constrictive pericarditis. Effusive constrictive pericarditis is a clinical entity in which patients who have a pericardial effusion, with or without cardiac tamponade, experience persistent symptoms and hemodynamic derangements after treatment and relief of the pericardial effusion. In some patients with constrictive pericarditis, pericardial inflammation results in an effusion, which is placed under pressure by the inelastic pericardium. Symptoms of low cardiac output, systemic congestion, and an elevated jugular venous pulse are seen, as in constrictive pericarditis; however, in patients with effusive constrictive pericarditis, a pericardial knock is absent and the y descent of the jugular venous pulse may be less prominent. Additionally, pulsus paradoxus may be present, which is not a typical finding of constrictive pericarditis. This disorder is caused by pericarditis involving the visceral layer of the pericardium. Thickening of the visceral layer of the pericardium can be difficult to detect with CT and other noninvasive imaging, and a high index of clinical suspicion is necessary to establish the diagnosis. In this patient, effusive constrictive pericarditis is suggested by the persistently elevated right atrial pressure following pericardiocentesis.

Similar findings in the jugular venous pulse can occur in patients with cor pulmonale or heart failure. With cor pulmonale, however, evidence of right ventricular dysfunction or chamber enlargement is usually seen on imaging. The clear lungs on auscultation do not support the presence of heart failure.

The presence of a normal electrocardiogram and the absence of the typical symptom of chest pain argue against recurrent acute pericarditis as a diagnosis. Additionally, acute pericarditis cannot explain this patient's pulsus paradoxus and elevated jugular venous pulse.