In a 35-year-old man presenting with fever, a macular exanthem, and mild ST‑segment elevation on electrocardiogram (ECG), what is the most likely diagnosis and how should the case be evaluated and managed?

Medical Advisory BoardAll articles are reviewed for accuracy by our Medical Advisory Board
Educational purpose only • Exercise caution as content is pending human review
Article Review Status
Submitted
Under Review
Approved

Last updated: October 20, 2026 • View editorial policy

Have a follow-up question?

Our Medical A.I. is used by practicing medical doctors at top research institutions around the world. Ask any follow up question and get world-class guideline-backed answers instantly.

Ask Question

Acute Viral Myocarditis

The most likely diagnosis is acute viral myocarditis presenting with an "infarct-like" pattern, which is classically seen in young men and requires urgent evaluation with cardiac biomarkers, echocardiography, and consideration of cardiac MRI to confirm the diagnosis and assess extent of myocardial involvement 1.

Clinical Presentation Pattern

This 35-year-old male's constellation of fever, macular rash, and ST-segment elevation fits the classic "infarct-like acute myocarditis" presentation that predominantly affects younger men 1. The presence of fever with rash strongly suggests a systemic viral illness with cardiac involvement, distinguishing this from acute coronary syndrome.

Immediate Diagnostic Approach

Priority Testing (in order):

  1. Cardiac troponin levels - Expected to be elevated in infarct-like myocarditis 1

  2. Echocardiography - Assess for:

    • Regional wall motion abnormalities
    • Left ventricular systolic function
    • Pericardial effusion (present in some cases but nonspecific)

  3. Coronary angiography consideration - While CMR may obviate this in select institutions for young patients without atherosclerotic risk factors and recent history consistent with acute myocarditis 1, many centers will still perform angiography to definitively exclude coronary artery disease given the ST elevations 2, 3

  4. Inflammatory markers - CRP, ESR to document systemic inflammation

Key Diagnostic Imaging

Cardiac MRI (CMR) is the definitive diagnostic test and should be performed once acute coronary syndrome is excluded 1. The expected CMR findings in viral myocarditis include:

  • Widespread myocardial edema
  • Patchy, often inferolateral necrosis on late gadolinium enhancement (LGE)
  • Subepicardial layers of edema and necrosis
  • Predominant involvement of lateral and inferolateral left ventricular wall 1

The Lake Louise Criteria have very high sensitivity and specificity in this infarct-like presentation due to the distinct regional distribution pattern 1.

Critical Differential Diagnoses to Exclude

Acute Pericarditis

Look for distinguishing features:

  • Concave (not convex) ST elevation
  • Diffuse ST elevation across multiple leads (not regional)
  • PR segment depression
  • ST/T wave ratio >0.24 in lead V6 4
  • Pericardial friction rub on examination

Tick-Borne Viral Infection

Given the macular rash and fever, consider tick-borne viral myocarditis, particularly in endemic regions 2. This would still be managed as viral myocarditis but may influence antimicrobial coverage decisions.

Brugada Syndrome (Fever-Induced)

While less likely given the macular rash, fever can unmask Brugada patterns with ST elevation in V1-V2 5, 6. However, Brugada typically shows an rSR' pattern rather than the diffuse changes expected in myocarditis.

Management Approach

Supportive Care

  • Hemodynamic monitoring
  • Arrhythmia surveillance (continuous telemetry)
  • Heart failure management if systolic dysfunction present

Specific Considerations

The evidence shows treatment with antiviral therapy, corticosteroids, and cardioprotective measures in documented viral myocarditis cases 2, though this should be guided by infectious disease consultation and specific viral etiology if identified.

Prognostic Implications

This infarct-like presentation may be associated with worse outcomes 1, requiring close monitoring for:

  • Development of heart failure
  • Ventricular arrhythmias
  • Progression to chronic myocarditis with scarring

Common Pitfalls to Avoid

  1. Do not administer thrombolytics - Misdiagnosing myocarditis as STEMI and giving thrombolytics can cause unnecessary harm 3

  2. Do not dismiss based on normal initial troponins - Serial troponins are essential as they may rise over time

  3. Do not overlook the rash - The macular rash is a critical clue pointing toward systemic viral illness rather than primary cardiac pathology

  4. Do not assume pericarditis without proper ECG criteria - Minor ST elevations with fever could be either condition, but the specific ECG morphology differs 4

References

2
Research

Suspected Tick-Borne Viral Infection-Associated Myocarditis Presenting with ST-Segment Elevation in V1-V3.

Turk Kardiyoloji Dernegi arsivi : Turk Kardiyoloji Derneginin yayin organidir, 2026

4
Research

Case Report: ST-Segment Elevation in a Man With Acute Pericarditis.

Frontiers in cardiovascular medicine, 2020

Related Questions

What type of myocardial infarction should be assigned to a patient with myocarditis presenting with chest pain, ST‑segment changes, and elevated troponin?
In a patient with anterolateral ST‑segment elevation on an electrocardiogram, how can I differentiate a benign early repolarization variant from an acute coronary syndrome and what is the appropriate management?
In a 24-year-old patient with an electrocardiogram showing slight ST‑segment elevation in leads aVL and V2, how should this finding be evaluated and managed?
I had an initial ECG showing an acute ST‑segment elevation myocardial infarction (STEMI), but my provider said it was likely stress‑related and the repeat 12‑lead ECG was normal with low‑decreasing troponin levels; does this mean I had a heart attack and what management is needed?
What ECG changes indicate anterolateral myocardial ischemia?
Does amitriptyline cause sedation and promote sleep?
Can calcium and vitamin D supplementation cause severe leg pruritus?
What is the recommended diagnostic approach for a patient with excessive daytime sleepiness, cataplexy, hypnagogic or hypnopompic hallucinations, sleep paralysis, or sudden loss of muscle tone during REM sleep?
How should valproic acid dosing be adjusted in a patient with low serum albumin?
What is the appropriate prednisone dose for systemic lupus erythematosus (SLE) with vasculitis?
What is the next step in management for a non‑diabetic patient on tirzepatide who has been vomiting for 12 hours despite receiving IV fluids, ondansetron, diphenhydramine, and famotidine?

Professional Medical Disclaimer

This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.