Myocarditis is a typical complication of many viral diseases1 and has also been described in other coronavirus diseases other than COVID-19.2, 3 However, it is only one possible complication of cardiac involvement in COVID-19 and requires an endomyocardial biopsy or a combination of suggestive clinical and imaging findings to reach a definitive diagnosis.4 Cardiovascular magnetic resonance (CMR) imaging is a cornerstone of the non-invasive diagnosis of myocarditis. Clinical studies have reported the diagnosis of myocarditis by CMR both in acute infections and in the post-acute phase.5 Cardiac involvement in COVID-19 was described early in the pandemic as a risk factor for poor outcomes.6 Inflammatory, thromboembolic and ischemic events are relevant complications of acute SARS-CoV-2 infection. However, even months after acute infection, many patients describe cardiopulmonary symptoms,7 and CMR indicates inflammatory processes,5 although their contribution to often complex clinical syndromes is questionable in some cases. Palmisano et al. investigated cardiac changes on CMR in 39 patients in the acute or post-acute phase of COVID-19 and found inflammatory changes in most patients.8 However, ischemic, valvular or other cardiomyopathies could also be diagnosed on the basis of CMR. The authors mention the heterogeneous patient population as a limitation of their study. On the contrary, this demonstrates the real additional impact of CMR since it has been shown that it can be used in a broad range of clinical scenarios. CMR can lead to a diagnosis independent of other accompanying factors and allows the exclusion or confirmation of possible differential diagnoses in the case of suspected virus-associated myocarditis. This is one of the most important tasks of cardiac imaging in the context of COVID-19. Especially potentially pre-existing but unknown cardiovascular diseases can be exacerbated in the context of SARS-CoV-2 infection and should therefore be excluded. Three major factors in Palmisano et al.'s study should be emphasized. First, the rate of diagnosed myocarditis (53%) appears to be very high. Although early studies on survivors of SARS-CoV-2 infection postulated high myocarditis rates, this could not be confirmed in actual autopsy studies,9 in which the use of histological criteria for the diagnosis of myocarditis showed a high degree of cardiac involvement but actual myocarditis in only 7.2% of the cases. In Palmisano et al.'s study, this can likely be explained by the good clinical pre-specification of the patients with a high clinical pre-test probability. This illustrates that CMR contributes to confirming the diagnosis, especially when it is well indicated. Second, the authors examined 17 patients with acute SARS-CoV-2 infection using CMR over a period of 5 months. Experience has shown that at several hospitals, this has not been done in fear of exposing staff to the risk of infection. This demonstrates the feasibility of CMR for infectious patients in a clinical setting. Third, with mostly normal biventricular function, non-invasive tissue characterization with an appropriate pre-test probability offers insights that goes far beyond pure functional or volumetric analyses. CMR diagnosis is not the first-line imaging method for diagnosis of myocarditis in mildly ill patients. However, in patients with a clinically justifiable diagnosis due to abnormal ECG and particularly echocardiographic findings and/or abnormal troponin levels accompanied with typical symptoms, CMR should be a diagnostic cornerstone in the acute and post-acute phase. The ongoing debate about short- and long-term cardiovascular consequences of COVID-19 needs to be put in a broader perspective than just the treatment of patients during pandemic. The great scientific effort and gained knowledge can potentially be used for other post-infectious syndromes, such as sequelae of Lyme disease, influenza and pneumococcal pneumonia. Moreover, this and similar studies showed that cardiovascular imaging in general and particularly advanced methods such as CMR and T1-derived parametric mapping should become a clinical routine that will serve not only for better understanding of cardiac involvement in COVID-19, but in overall better acceptance of CMR in everyday clinical practice in large spectrum of cardiovascular diseases. Open Access funding enabled and organized by Projekt DEAL.
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Mar 18, 2023
Pratik Sinha + 1
Open Access
