Pericarditis and myocarditis share common aetiological agents (e.g. viruses and also systemic inflammatory diseases). In clinical practice coexistence and overlapping of pericarditis and myocarditis may occur ranging from forms with pure pericarditis, prevalent pericarditis (myopericarditis), prevalent myocarditis (perimyocarditis) to pure myocarditis (Fig. 12.1) [1–3]. In an attempt to provide a clinically useful definition of mixed inflammatory syndromes, the following definitions were proposed [1–4].

The usual presentation of myopericardial inflammatory syndromes is “pericarditic” chest pain during or following a flu-like syndrome or gastroenteritis, typically in a young male (Table 12.1) [1–3].

In clinical practice, troponin elevation is detected at the initial evaluation at the emergency department [3–6]. Pericardial rubs may be present in forms with prevalent pericarditis. The ECG usually shows widespread ST-segment elevation with possible atypical features and evolution (e.g. localized changes, T wave inversion before ST-segment normalization as in acute coronary syndromes) (Fig. 12.2). Cardiac arrhythmias may be detected usually as premature beats either supraventricular or ventricular. Atrial fibrillation may also occur, while other ventricular arrhythmias are more common in patients with pure myocarditis [3–6].

Patients with myopericarditis, which is pericarditis with mild myocarditis involvement, represent the vast majority of cases encountered in clinical practice. The usual presentation with chest pain may mimic an acute coronary syndrome, which is the main differential diagnosis. On the contrary patients with perimyocarditis may complain a pseudo-infarctual presentation, as well as heart failure or arrhythmic presentation, reflecting the degree of myocardial involvement [1–5].

There are three main aetiological categories: idiopathic, infectious and immune mediated (Table 12.2). As mentioned, pericarditis and myocarditis share similar aetiological agents. This aetiological background provides the explanation for overlapping syndromes, although it is not clear why subjects develop pericarditis, myocarditis, mixed forms or no clinical manifestations, despite similar exposition to the same aetiological agent. Unknown genetic and immunological factors probably play a significant role, as well as hormonal factors, since myocardial involvement is more prominent in paediatric cases, as well as young adult males. Limited clinical data on the causes of myopericarditis suggest that viral infections are among the most common causes in developed countries. The most frequent viruses encountered in Western Europe and North America include Coxsackieviruses (especially Coxsackie B), Adenoviruses, Cytomegalovirus (CMV), Epstein-Barr Virus (EBV), Influenza virus, Hepatitis A and C virus, Varicella Zoster Virus (VZV) and Parvovirus B19. Fulminant cases have been described in paediatric and adult cases during the pandemic 2009 (H1N1) influenza A, but especially in forms with predominant myocardial involvement, which should be probably more correctly described as myocarditis or perimyocarditis cases, instead of myopericarditis cases [2].