Myocardial Injury Seen on MRI in 54% After Troponin-Positive COVID

Debra L. Beck

February 23, 2021

Editor's note: Find the latest COVID-19 news and guidance in Medscape's Coronavirus Resource Center.

About half of 148 patients hospitalized with COVID-19 infection and elevated troponin levels had at least some evidence of myocardial injury on cardiac magnetic resonance (CMR) imaging 2 months later, a new study shows.

"Our results demonstrate that in this subset of patients surviving severe COVID-19 and with troponin elevation, ongoing localized myocardial inflammation, whilst less frequent than previously reported, remains present in a proportion of patients and may represent an emerging issue of clinical relevance," write Marianna Fontana, MD, PhD, from University College London, and colleagues.

The cardiac abnormalities identified were classified as nonischemic (including "myocarditis-like" late gadolinium enhancement [LGE]) in 26% of the cohort; as related to ischemic heart disease (infarction or inducible ischemia) in 22%; and as dual pathology in 6%.

Left ventricular (LV) function was normal in 89% of the 148 patients. In the 17 patients (11%) with LV dysfunction, only four had an ejection fraction below 35%. Of the nine patients whose LV dysfunction was related to myocardial infarction, six had a known history of ischemic heart disease.

MRI scan of damaged heart, basal, mid, and apical slices. Blue indicates reduced blood flow, orange is good blood flow. In this figure the inferior part of the heart shows dark blue, so the myocardial blood flow is very reduced. The black and white angiography shows that the vessel which supplies the blood to this part of the heart is occluded.

No patients with "myocarditis-pattern" LGE had regional wall motion abnormalities, and neither admission nor peak troponin values were predictive of the diagnosis of myocarditis.

The results were published online February 18 in the European Heart Journal.

Glass Half Full

Taking a "glass half full" approach, cosenior author Graham D. Cole, MD, PhD, noted on Twitter that nearly half the patients had no major cardiac abnormalities on CMR just 2 months after a bout with troponin-positive COVID-19.

"We think this is important: even in a group who had been very sick with raised troponin, it was common to find no evidence of heart damage," said Cole, from the Royal Free London NHS Foundation Trust.

"We believe our data challenge the hypothesis that chronic inflammation, diffuse fibrosis, or long-term LV dysfunction is a dominant feature in those surviving COVID-19," the investigators conclude in their report.

In an email, Fontana explained further: "It has been reported in an early 'pathfinder' study that two-thirds of patients recovered from COVID-19 had CMR evidence of abnormal findings with a high incidence of elevated T1 and T2 in keeping with diffuse fibrosis and edema. Our findings with a larger, multicenter study and better controls show low rates of heart impairment and much less ongoing inflammation, which is reassuring."

She also noted that the different patterns of injury suggest that different mechanisms are at play, including the possibility that "at least some of the found damage might have been pre-existing, because people with heart damage are more likely to get severe disease."

The investigators, including first author Tushar Kotecha, MBChB, PhD, from the Royal Free London NHS Foundation Trust, also note that myocarditis-like injury was limited to three or fewer myocardial segments in 88% of cases with no associated ventricular dysfunction, and that biventricular function was no different than in those without myocarditis.

"We use the word 'myocarditis-like' but we don't have histology," Fontana said in an email. "Our group actually suspects a lot of this will be microvascular clotting (microangiopathic thrombosis). This is exciting, as newer anticoagulation strategies — for example, those being tried in RECOVERY — may have benefit."

Aloke V. Finn, MD, from the CVPath Institute in Gaithersburg, Maryland, wishes researchers would stop using the term myocarditis altogether to describe clinical or imaging findings in COVID-19.

"MRI can't diagnose myocarditis. It is a specific diagnosis that requires, ideally, histology, as the investigators acknowledged," said Finn in an interview.

His group at CVPath recently published data showing pathologic evidence of myocarditis after SARS-CoV-2 infection, as reported by | Medscape Cardiology.

"As a clinician, when I think of myocarditis, I look at the echo and an LV gram, and I see if there is a wall motion abnormality and troponin elevation, but with normal coronary arteries. And if all that is there, then I think about myocarditis in my differential diagnosis," he said. "But in most of these cases, as the authors rightly point out, most patients did not have what is necessary to really entertain a diagnosis of myocarditis."

He agrees with Fontana's suggestion that what the CMR might be picking up in these survivors is microthrombi, as his group saw in their recent autopsy study.

"It's very possible these findings are concordant with the recent autopsy studies done by my group and others in terms of detecting the presence of microthrombi, but we don't know this for certain because no one has ever studied this entity before in the clinic and we don't really know how microthrombi might appear on CMR."

Largest Study to Date

The 148 participants (mean age, 64 years; 70% male) in the largest study to date to investigate convalescing COVID-19 patients who had elevated troponins — something identified early in the pandemic as a risk factor for worse outcomes in COVID-19 — were treated at one of six hospitals in London.

Patients who had abnormal troponin levels were offered an MRI scan of the heart after discharge and were compared with those from a control group of patients who had not had COVID-19 and with 40 healthy volunteers.

Median length of stay was 9 days, and 32% of patients required ventilatory support in the intensive care unit.

Just over half the patients (57%) had hypertension, 7% had had a previous myocardial infarction, 34% had diabetes, 46% had hypercholesterolemia, and 24% were smokers. Mean body mass index was 28.5 kg/m2.

CMR follow-up was conducted a median of 68 days after confirmation of a COVID-19 diagnosis.

On Twitter, Cole noted that the findings are subject to both survivor bias and referral bias. "We didn't scan frail patients where the clinician felt [CMR] was unlikely to inform management."

The findings, said Fontana, "say nothing about what happens to people who are not hospitalized with COVID, or those who are hospitalized but without elevated troponin."

What they do offer, particularly if replicated, is a way forward in identifying patients at higher or lower risk for long-term sequelae and inform strategies that could improve outcomes, she added.

Eur Heart J. Published online February 18, 2021. Full text


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