ISSN 2398-2969      

Heart: myocarditis

icanis

Introduction

  • Myocardial inflammation, infiltrate and necrosis/degeneration of adjacent myocytes.
  • Cause: classic myocarditis is related to inflammation due to exposure to either discrete external antigens such as bacteria, viruses, parasites or internal triggers such as autoimmune disease. In people, drug/toxin induced myocarditis is also recognized.
  • Signs: variable - arrhythmias to congestive heart failure (CHF) and sudden death.
  • Diagnosis: history and clinical signs (systemic illness), heart auscultation, electrocardiography, echocardiography, cardiac troponin I, endomyocardial biopsy, serology, blood culture.
  • Treatment: specific treatment against inciting element plus treatment of arrhythmia/CHF.
  • Prognosis: depends on severity and inciting agent/cause.

Pathogenesis

Etiology

Infectious causes

Viral myocarditis

Protozoal myocarditis 

Bacterial myocarditis 

Predisposing factors

General

  • Immunosuppression.
  • Debility.

Specific

  • Exposure to infectious agent or use of myocardiotoxic substances such as doxorubicin Doxorubicin.

Pathophysiology

  • Inflammation of heart muscle caused by infectious/toxic agent(s) affecting pericardium, myocytes, interstitial or vascular tissue of heart.
  • May be acute or chronic if infectious.
  • Can result in cardiac dysfunction.
  • Infection may arise locally, including valvular tissue, or be spread from distant sites, eg dental, prostate, skin, uterus, lung.
  • Infection/toxicity → toxin (local or blood borne)/immune-complex/direct invasion → vasculitis/myocyte damage → myocardial inflammation → cardiac dysfunction = arryhthmias/CHF.
  • Often concurrent signs of systemic infection/toxicity.
  • Severe systemic disease, eg GDV, IMHA - sympathetic 'storm' and release of free radicals - myocardial necrosis - arrhythmias.

Timecourse

  • May have acute (days), or chronic (months) course.
  • Acute disease may progress to a form of cardiomyopathy and eventually heart failure.

Diagnosis

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Treatment

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Prevention

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Outcomes

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Further Reading

Publications

Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Ferasin L et al (2021) Infection with SARS-CoV-2 variant B.1.1.7 detected in a group of dogs and cats with suspected myocarditis. Vet Rec 189(9), e944 PubMed.

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