PC2168: False-positive Troponins in a Pediatric Patient with Post-vaccine Myocarditis

Introduction: As the worldwide effort to administer vaccines for the prevention of COVID-19 has continued, the medical community increasingly recognizes post-mRNA vaccination myocarditis. Surveillance of this rare complication shows most cases are in males with median age of 18. The illness course is usually mild and self-limited. Small data sets suggest that markers of myocardial damage (cardiac troponins) resolve within days to weeks. Separately, the novel cardiac biomarker high-sensitivity troponin T (hs-cTnT) has become common in the management of adult cardiac injury however lacks consensus on interpretation and utility in pediatric populations. Adult literature warns of falsely elevated cardiac troponin T (cTnT) and I (cTnI) in several clinical scenarios.

Case Description: A 12-year-old male with ADHD, allergic rhinitis, tree nut allergies, and no prior COVID-19 disease presented to a community ED with acute onset pleuritic, substernal chest pain 3 days after receiving his 2nd dose of Pfizer-BioNTech mRNA vaccine. Lab testing revealed elevated cTnI with normal pro-BNP, d-dimer, CMP, CBC, and EKG. He was transferred to a children’s hospital where repeat EKG and echocardiogram were normal. Additional testing showed rising cTnI and negative viral PCR and Lyme panels. Serial cTnI monitoring demonstrated peak level at 8 hours and then consistent downtrend until discharge [figure 1]. Chest pain resolved within 12 hours, and he was discharged with strict exercise precautions. Outpatient follow-up was performed at a facility utilizing hs-cTnT biomarker, not cTnI. Outpatient lab trend and relevant clinical studies are depicted [figure 2]. Final troponin levels were collected at 7 months post-diagnosis in consideration of booster vaccine. Alternative lab assay results from that sample are shown.

Discussion: We report a 12-year-old male with post-mRNA vaccination myocarditis and persistently elevated hs-cTnT over 7 months despite rapid recovery and no clinical evidence of ongoing cardiac injury. Elevated troponin levels are important diagnostic discriminators in cases of myocarditis. Time to resolution of elevated troponins in post-vaccination myocarditis patients is not frequently reported but select case series show resolution at or near the time of discharge from the hospital, making this persistent elevation unusual. As the patient’s clinical picture did not match his persistently elevated troponins, we considered a laboratory false-positive. Typically, heterophile antibodies, fibrin clots, rheumatoid factor, and hemolysis are implicated. Use of an alternative laboratory and testing other troponin isomers showed normal cTnI, strongly suggesting false-positive hs-cTnT. This suggests that our patient may have had no in vivo troponin leak beyond the timeframe expected in myocarditis.

Conclusion: This case bolsters the emerging literature on post-vaccine myocarditis and cautions providers about diagnostic and prognostic difficulties – including risks of increased blood draws and family anxieties – when using hs-cTnT in pediatric patients with suspected myocardial injury.