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4.3.2 Heart failure presentation

Patients with myocarditis presenting with acute HF, in particular when associated with left ventricular dysfunction (LVEF ≤ 40%), should be considered as a high-risk group, and their prognosis largely depends on the short-term response to therapy.28,62 Clinical presentation may range from unexplained impaired ventricular function (with or without dilated LV), new onset or worsening HF (usually over 2 weeks to 3 months), to rapidly progressive refractory HF and cardiogenic shock. Fulminant myocarditis presenting with HF has a higher rate of cardiac death and heart transplantation (HT) both in the short and long term, compared with patients with LV dysfunction without FM (see Section 4.2.2).56,73,74 In these scenarios, GCM and EM are independently associated with increased mortality.56,75 An algorithm for the proposed workflow is shown in Figure 10. As a central scheme, the workflow follows the CHAMPIT approach, provided in the 2021 ESC Guidelines for the diagnosis and treatment of acute and chronic heart failure.12 One should be aware that arrhythmias can be a presentation of myocarditis, as well as an ‘alternative cause’ of HF outside the suspicion of myocarditis.

4.3.3 Presentation with arrhythmias

Patients with AM with new, recurrent, or unexplained arrhythmias may have a wide spectrum of symptoms, ranging from palpitations to syncope or life-threatening arrhythmias causing aborted SCD.10,76 Supraventricular arrhythmias, especially AF,63,77 are more common in the presence of concomitant pericarditis and PEff, while atrioventricular blocks (AVBs) or sustained VA are generally, but not exclusively, associated with LV dysfunction and HF. Patients with advanced AVB or sustained VA should be considered as high risk, even in the absence of LV dysfunction. Ventricular fibrillation (VF)/cardiac arrest occurs in about 2.5% of myocarditis-related hospitalizations.78 Patients with sustained VA during AM have a high risk of recurrence.79 Patients with GCM (see Section 9.3) or CS (see Section 9.4) are at a high risk of VA, with a prevalence of >25%.80–82 Scar-related VA can occur at any time during follow-up, even after inflammation resolution. However, polymorphic and irregular VA are more common during the active inflammatory phase, whereas monomorphic and regular VA are associated with healed myocarditis with residuals.83 Consistently, catheter ablation of ventricular tachycardia (VT) is more effective when performed in the post-inflammatory stage of the disease rather than during AM.84 AVB is a common feature of myocarditis related to non-viral infections (i.e. CD, LC, diphtheria),85 and can also be an initial presentation of CS. In patients with arrhythmic presentation, genetic testing for CMP [ARVC/dilated CMP (DCM)/non-dilated left ventricular CMP (NDLVC)] should be considered (see Section 5.3).

An algorithm for the proposed workflow is shown in Figure 11.

4.3.4 Sudden cardiac death

One of the causes of SCD in young adults is myocardial inflammation associated with fatal arrhythmias. Sudden cardiac death attributed to myocarditis among autopsied patients ranged from 1.1% to 12%,87,88 and males show higher incidence rates of SCD than females, with an incidence rate ratio of 2.2.88 Most individuals are asymptomatic before SCD; however, between 18% and 48% of patients present with symptoms, including viral illness/malaise, syncope, nausea/abdominal pain, chest pain, and palpitations.87,88 Only 5% show cardiac symptoms in conjunction with an infective process.87 These data highlight the need to suspect a diagnosis of myocarditis early enough. Late gadolinium enhancement in the mid-wall layer of the anteroseptal myocardial segments has been associated with higher rates of mortality and major VA, including SCD,3,89,90

even in the presence of preserved LVEF. Septal involvement in myocarditis can be associated with a worse prognosis in the presence of a specific genetic background, such as pathogenic desmosomal gene variants (see Section 5.3).91,92 Further studies are necessary to confirm these data.

4.3.5 Presentation of myocarditis with a potential

genetic background A complex interaction between genetic background and inflammation might be responsible for the heterogeneity of the clinical presentation of myocarditis. An inflammatory stimulus of the heart might unveil an increased genetic susceptibility to develop overt LV dysfunction or arrhythmogenic phenotypes. In this setting it is important to consider additional features, such as a family history of myocarditis/pericarditis, CMP, or SCD. Autosomal dominant gene defects may be associated with myocarditis.93–95 Certain autosomal recessive defects in genes encoding various components of the cardiac structure can predispose young individuals to myocarditis.95,96 Different studies reported that patients with myocarditis and evidence of pathogenic/likely pathogenic (P/LP) desmosomal gene variants (mostly with DSP variants) have a higher incidence of adverse cardiovascular events, especially myocarditis recurrence and VA, than patients without.91,94 Episodes of acute chest pain with troponin elevation and normal coronary arteries may occur in about 15% of patients with DSP mutations and are associated with LV LGE in about 90% of cases.97 Specific genetic P/LP variants may increase the susceptibility to superimposed myocarditis in ARVC, which may be the first clinical presentation in the natural history of the disease.64,98 The presence of so-called ‘hot phases’ (chest pain episodes accompanied by ECG changes and troponin release) represents a possible clinical presentation of ARVC, which often occurs in paediatric and young patients, as well as carriers of DSP genetic variants.99–101 Currently, the role of ‘hot phases’ in disease progression, as well as in arrhythmic risk stratification, remains to be clarified. For more details see Section 5.3.

4.4 Clinical stages of pericarditis

4.4.1. Acute pericarditis Acute pericarditis is an inflammatory pericardial syndrome with or without PEff with an onset of ≤4 weeks. The clinical diagnosis is usually characterized by pleuritic and/or positional chest pain (>80% of cases). Dyspnoea is more common in the elderly.45,102 Physical examination may be characterized by pericardial friction rubs in up to one-third of cases, which could disappear with the presence of PEff. Pericardial effusion has been reported in up to 60% of cases, and it is usually mild. ECG changes, especially PR depression as an early sign and widespread ST-segment elevations, have been reported in up to 60% of cases, especially in young patients. This is suggestive of concomitant myocardial involvement, at least of mild degree.

ESC Guidelines                                                                                                                                                                                          3973

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