Hypersensitivity myocarditis: Findings in native and transplanted hearts

Area of Science:

• Cardiology
• Transplantation Immunology
• Pathology

Background:

• Hypersensitivity myocarditis (HM) is a rare but serious cardiac condition.
• Understanding its prevalence and associations in heart transplant recipients is crucial for patient management.

Purpose of the Study:

• To determine the prevalence of histologic hypersensitivity myocarditis in explanted hearts from heart transplant recipients.
• To investigate clinical and histologic features associated with HM in this population.

Main Methods:

• Histologic examination of seven explanted hearts from 288 heart transplants (2.4% prevalence).
• Review of clinical histories, including drug allergies, reactions, and peripheral eosinophilia.
• Assessment of acute rejection episodes and associated eosinophilic infiltration post-transplant.

Main Results:

• Seven explanted hearts showed histologic evidence of HM (2.4% prevalence).
• Pre-transplant history included drug allergy (3 patients) and peripheral eosinophilia (3 patients).
• Four patients experienced acute rejection (ISHLT grade 2-4) with eosinophils within 3 weeks post-transplant.

Conclusions:

• Hypersensitivity myocarditis may be an under-recognized condition in heart transplant recipients.
• Increasing prevalence of HM in native and transplanted hearts warrants further investigation.
• HM should be considered in the differential diagnosis of cardiac dysfunction and rejection post-transplant.