What does this research mean for the field?

Progressive conduction abnormalities on serial electrocardiograms can serve as an early manifestation of immune checkpoint inhibitor-associated myocarditis, potentially preceding troponin elevation. Novelty: ClaimNovelty.INCREMENTAL. Consensus alignment: ConsensusAlignment.NEUTRAL.

What question did this study set out to answer?

To describe the progressive cardiac conduction abnormalities associated with immune checkpoint inhibitor cardiotoxicity and highlight the role of serial electrocardiograms in early detection.

May 23, 2026JACC Case ReportsOpen Access

Progressive Conduction Disease on Serial ECGs Revealing Immune Checkpoint Inhibitor–Associated Myocarditis and Myositis

Q: What is the clinical evidence from this study?

Study design: Case Report. Population: Immune Checkpoint Inhibitor-Associated Myocarditis and Myositis (n=1). Intervention: cemiplimab.

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Key result

Progressive ECG conduction abnormalities can signal fatal cemiplimab-induced myocarditis before troponin rises.

Why the study?

Immune checkpoint inhibitors are effective treatments for cancer but carry cardiovascular toxicity risks.

Key Points

To describe the progressive cardiac conduction abnormalities associated with immune checkpoint inhibitor cardiotoxicity and highlight the role of serial electrocardiograms in early detection.
Clinical, laboratory, and electrophysiological evaluation of an 83-year-old male receiving cemiplimab for advanced squamous and basal cell carcinoma (N=1).
Diagnostic procedures included serial electrocardiograms, invasive coronary angiography, echocardiography, cardiac PET, and deltoid muscle biopsy.
Serial ECGs captured the progression from atypical atrial flutter with new right bundle branch block to complete heart block with ventricular escape rhythms.
Laboratory testing showed high-sensitivity troponin T elevated to 1,716 ng/mL and creatine phosphokinase elevated to 3,888 U/L, complicated by SCAI Stage C cardiogenic shock.
Deltoid muscle biopsy confirmed immune-mediated necrotizing inflammatory myopathy, and the condition was steroid-refractory and fatal despite high-dose methylprednisolone, intravenous immunoglobulin, and permanent pacemaker placement.

Study Design

Type

Case Report (n=1)

Multicenter

Structured PICO

Population

1 83-year-old male with advanced skin cancer treated with cemiplimab who developed progressive conduction disease and cardiogenic shock due to immune checkpoint inhibitor toxicity.

Exposure

Cemiplimab (1 dose). Subsequent management for toxicity included high-dose methylprednisolone (1 mg/kg daily), intravenous immunoglobulin (0.5 g/kg daily), and transvenous followed by permanent pacemaker implantation.

Progressive conduction abnormalities on serial ECGs may serve as a critical, early pre-troponin diagnostic indicator for fatal immune checkpoint inhibitor-associated myocarditis.

Limitations

Patient postponed oncology follow-up and declined second infusion, limiting structured monitoring
Cardiac biopsy was deemed too high risk to perform

Discussion

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Implication

May support serial ECG vigilance in cemiplimab recipients; leaves open whether surveillance improves outcomes in prospective cohorts.

Cite This Study

Nelson et al. (2026) conducted a case report in Immune Checkpoint Inhibitor-Associated Myocarditis and Myositis (n=1). cemiplimab was evaluated. Progressive conduction abnormalities on serial ECGs were an early manifestation of fatal cemiplimab-associated myocarditis and myositis, preceding troponin elevation.

synapsesocial.com/papers/6a1143fc48a409a3a49de796 https://doi.org/10.1016/j.jaccas.2026.107825

Topics

Myocarditis

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Progressive Conduction Disease on Serial ECGs Revealing Immune Checkpoint Inhibitor–Associated Myocarditis and Myositis

Key Points

Study Design

Structured PICO

Limitations

Discussion

Implication

Cite This Study

Topics

Progressive Conduction Disease on Serial ECGs Revealing Immune Checkpoint Inhibitor–Associated Myocarditis and Myositis

Key Points

Study Design

Structured PICO

Limitations

Discussion

Implication

Cite This Study

Also Consider

Topics

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