Reply to the Letter to the Editor: “Cardiac magnetic resonance imaging of myocarditis and pericarditis following COVID-19 vaccination: a multicenter collection of 27 cases”

by Emanuele Di Dedda, Marco Francone (marco.francone@hunimed.eu)

Cardiac magnetic resonance imaging of myocarditis and pericarditis following COVID-19 vaccination: a multicenter collection of 27 cases

Dear Editor,

We would, first of all, like to thank Dr. Mungmunpuntipantip and colleagues for the interest in our report.

As specified in the paper, we can confirm that we based our data collection on the temporal correlation between the date of vaccine injection and the date of CMR, which is the only objective criterion applicable in this clinical setting. This purely temporal approach is obviously limited and potentially comprehend alterative causes of myo-pericarditis, for which we have decided to extend data collection to a similar cohort of non-COVID 19 patients with a similar diagnostic suspect.

There might be many causative, possibly concomitant, factors behind myopericarditis in our population, the most important of which is a COVID-19 latent disease, without excluding other known infective or non-infective diseases.

What can be surely said on this matter is that several international government registries have confirmed, based on different clinical studies, the increased risk of cardiac inflammation in population, especially in young males, after vaccine administration [1, 2] and have officially added this type of reaction to the list of possible adverse events.

As expected, regarding specific CMR imaging features of myopericarditis after vaccine administration, we couldn’t find any specific or pathognomonic features. This might be because of the limited case series or, more probably, because the origin of the condition cannot be radiologically distinguished among the others, as also suggested in the letter.

Despite the known existence of many causative factors, we showed that CMR can confirm non-invasively the presence and extension of cardiac involvement in cases of suspected myopericarditis after vaccine administration, and this could guide subsequent clinical decisions, especially considering that the clinical and radiological setting of the condition is new, and prognostic features consequently mostly unexplorated.

We would like to remark also that the estimated incidence observed in our paper (3.4 cases/million doses, by CMR) and in international registries (< 50 cases/million doses, as shown in Figure 2 of the paper) is still very low while the 3-dose vaccination campaign conducted in several parts of the world has been shown to be safe and very effective against COVID-19 related morbidity and mortality [3].