COVID-related myocarditis: what you need to know

MYOCARDITIS is increasingly diagnosed in the COVID-19 era, but it’s at least partly due to increased awareness of the condition and advances in detecting milder cases, experts say.

Speaking with InSight+, Associate Professor Andrew MacIsaac, Director of Cardiology at St Vincent’s Hospital in Melbourne, stressed that myocarditis remained a “rare and mostly mild condition”.

His team has seen several cases of SARS-CoV-2-related myocarditis since 2020 and one definitive case of myocarditis related to the Comirnaty (Pfizer) vaccine.

“We have had to admit some people with myocarditis, but we haven’t had anyone with long term complications from having it,” Associate Professor MacIsaac said.

Awareness of the condition has grown as a result of its association with COVID-19 and mRNA COVID-19 vaccines, so that cardiologists are seeing increasing numbers of suspected cases, he said.

“The vast majority of people who are referred to cardiologists with suspected myocarditis don’t have myocarditis,” he said. “There is a lot of anxiety in the community and brief chest pains are very common when people are anxious.”

Many of today’s cases were mild and would not have been diagnosed a decade ago, Associate Professor MacIsaac said.

“When doctors used to think of myocarditis, they thought of a very serious condition where someone might be febrile with a viral illness, chest pain, and have acute heart failure,” he said. “However, it’s becoming recognised that myocarditis is a spectrum.”

Cardiac magnetic resonance imaging (MRI) had proved a breakthrough in diagnosing the condition, he said, enabling cases that might previously have been described as “atypical chest pain”, “no diagnosis made” or sometimes “suspected myocardial infarction” to be definitively diagnosed.

Professor MacIsaac urged GPs to be guided by the severity of a patient’s symptoms when considering suspected cases of myocarditis.

“If a GP is concerned because their patient has chest pain and they suspect it might be myocarditis they should do an [electrocardiogram (ECG)] to make sure its normal,” he said. “Then check the troponin and arrange an echocardiogram, and if the troponin or the echocardiogram are abnormal, specialist advice is required.”

In a case study published in the MJA, a patient with COVID-19 mRNA vaccine (Comirnaty)-induced myocarditis was treated with ibuprofen, pantoprazole and bisoprolol, with complete resolution of symptoms within 24 hours.

The 20-year-old man had developed chest pain 48 hours after administration of his second dose of the Comirnaty vaccine, and also had fevers and diaphoresis. His first dose had been uncomplicated.

He had sinus tachycardia with global ST elevation and elevated troponin. No abnormality was detected with echocardiogram, but cardiac MRI showed epicardial late gadolinium enhancement over the mid and apical lateral segments, consistent with myocarditis.

The authors from the Royal Melbourne Hospital said the case was consistent with a recent case series of 61 patients with COVID-19 vaccination-related myocarditis, in which 90% had symptom resolution, with a median hospitalisation duration of 4.6 days.

“COVID-19 mRNA vaccine-related myocarditis is an extremely rare and mild complication, and is much less frequent than myocarditis secondary to SARS-CoV-2 infection,” they wrote, adding:

“Management in the primary care or outpatient setting is appropriate if presentation is mild and if ECG, troponin and inflammatory markers can be reviewed within 12 hours.”

The authors stressed that the benefit–risk assessment for COVID-19 mRNA vaccination was still overwhelmingly favourable for all age and sex groups, including males aged 12–29 years, who were at highest risk of vaccine-related myocarditis.

The Australian Technical Advisory Group on Immunisation (ATAGI) notes that COVID-19 is estimated to cause myocarditis at a rate of 11.0 events per 100 000 persons, whereas the Comirnaty (Pfizer) vaccine has been estimated to cause myocarditis at an overall rate of 2.7 events per 100 000 persons.

By 23 January 2022, 431 likely myocarditis cases and 774 likely pericarditis cases related to the Comirnaty vaccine had been reported to the Therapeutic Goods Administration, out of 31.6 million doses given. A further 46 likely myocarditis and 57 likely pericarditis cases linked to Spikevax (Moderna) were also reported, out of 2.7 million doses. For both vaccines, the data include several cases among adolescents.

The Royal Australian College of General Practitioners spokesperson, Professor Mark Morgan of Queensland’s Bond University, said a GP’s decision to refer a patient with suspected myocarditis or pericarditis took into account not only clinical factors but also psycho-social ones and the capacity of general practice to manage the situation safely and promptly.

“GPs can conduct and interpret ECGs, request and interpret the results of blood tests and make clinical assessments and try to make sense of undifferentiated symptoms such as chest wall pain, heart pain and combinations of the two,” he said.

“However, the management of a patient may change depending on whether the patient has support available to them at home and can get back to us for regular reviews, or if they are presenting on a Saturday afternoon when a deputising service is about to take over.”

The federal government introduced a Medicare Benefits Schedule item in January 2022 for cardiac MRI to assist in diagnosing myocarditis that may occur following COVID-19 vaccination with an mRNA vaccine. Only consultant physicians can order the test under the temporary item, and only after inconclusive results from echocardiogram, troponin and chest x-ray. The item is timed to coincide with the COVID-19 vaccine and booster vaccine rollout and will expire in June. The schedule fee is $855.20.

Professor MacIsaac applauded the decision to fund the test, and said it should be made a permanent item and broadened to test for other heart conditions.

Associate Professor David Prior, deputy director of cardiology at St Vincent’s hospital in Melbourne, also welcomed the funding, but said it was “a little bit weird” given the federal government in 2016 rejected a submission by the Cardiac Society of Australia and New Zealand to expand funding for cardiac MRI.

“If the government thinks it is sensible to fund cardiac MRI for myocarditis related to the vaccine, then it doesn’t make sense not to fund it in an ongoing way for suspected myocarditis unrelated to COVID-19 vaccination and other cardiac diseases which have much worse outcomes,” he said.

Ironically, St Vincent’s hospital was not using the new item number to fund cardiac MRI, he said.

“Because there are almost no item numbers for cardiac MRI funded through Medicare, much of the cardiac MRI in Australia is done through teaching hospitals that have an interest in it and often self-fund it, and they tend to be done therefore on cardiac MRI machines that are not licensed for Medicare,” he said.

“So, if you’re going to do MRI scans for COVID- vaccine-related myocarditis, it would necessitate 6you moving to a different machine – the one you usually do hips and knees and backs on.

“We’ve made the decision to just keep using our usual machine, which is our best one, even though we don’t get money for it,” he added.

Associate Professor Prior agreed that cardiac MRI was now picking up mild cases that in the past wouldn’t have been detected.

“Are we now picking up cases where it doesn’t matter? I don’t think we know the answer to that yet,” he said. “What we do know is that with cardiac MRI, you can see things which you can’t see any other way, sometimes providing the definitive diagnosis that changes the whole treatment paradigm.”

He gave a typical example of a symptomatic patient who had elevated troponin but a normal angiogram.

“With cardiac MRI, a common thing we find under those circumstances is myocarditis, but sometimes you discover they have had [a myocardial infarction] and the abnormality was not seen on the angiogram,” he said. “So, from the cardiac MRI, we know whether to treat with medications to prevent further myocardial infarction or to look at appropriate therapy for myocarditis.”

Associate Professor Prior said mild cases of myocarditis could be treated with pain relief and observation, while cases with abnormal heart function might require antihypertensives. Cases should not exercise competitively for 6 months, and only after cardiac testing, he added.

Australian guidelines on myocarditis and pericarditis after mRNA COVID-19 vaccines are available here.

Separate guidelines for assessment of possible vaccine-induced pericarditis or myocarditis in children and adolescents presenting to the ED are available here.