Newly diagnosed acute pericarditis requires rapid risk prediction in three major categories:

1. Short-term, immediately threatening, complications.

2. Aetiology/probable aetiology.

3. Significant long-term complications.

Whom to keep in hospital involves the first and to some extent the second of these categories.

RISK PREDICTION

Imazio and colleagues have greatly clarified risk prediction and management of acute and recurrent pericarditis through series of long overdue, carefully designed, prospective investigations.1^–4 Fortunately, their evidence-based results largely confirm many solid observational studies by single and multicentre investigators—notably, Adler,5 Brucato,6 Permanyer7 and their colleagues. A variable element of myocarditis is common with most acute pericarditis (myopericarditis), often clouding the complete evaluation of the patient. In this issue of Heart, Imazio and colleagues add to their many contributions by clarifying the differential diagnosis of myopericarditis (see article on page 498).8

While admitting all patients to hospital would cover all possibilities, Imazio’s probabilistic approach avoids the inconveniences, inefficiencies and expense of universal admission.1 The immediate concern is always for the threatening short-term consequences which may be in progress at the time of diagnosis or appear shortly thereafter, including cardiac tamponade9 and disability due to pain, fever, toxicity and underlying diseases—diagnosed and undiagnosed—notably, malignancies, vasculitides and sepsis.10 Thus categories 1 and 2 above are linked. Moreover, because of frequent symptomatic, electrocardiographic and serum enzyme level similarities, diagnostic differentiation further necessitates considering mutually mimicking conditions like acute pericarditis, myocarditis …