Chagas heart disease
- Lesion
Chagas disease, caused by a parasite spread by triatomine bugs, can scar the heart years later, causing block, aneurysms and heart failure.
What it is
Chagas disease is caused by Trypanosoma cruzi, transmitted mainly by the faeces of triatomine bugs (in Colombia known as ‘pitos’), and also by transfusion, from mother to child, by contaminated food and by transplantation. After an often silent acute phase, most people stay in an indeterminate phase for life, but roughly a fifth to a third develop chronic Chagas cardiomyopathy decades later. It is a chronic fibrosing myocarditis driven by persistent parasites and the immune response, with damage to the conduction system, the autonomic nerves and the microvasculature.
Structure
- Gross: enlarged dilated heart; thin apical aneurysm, often with thrombus; patchy scars.
- Microscopy: lymphocytic infiltrate with myocyte damage and extensive interstitial fibrosis; loss of ganglion cells; parasites rarely seen in the chronic phase.
Step by step
- Trypanosomes enter through the bite wound or mucosa and invade cells.
- In the acute phase they multiply as amastigotes inside myocytes, causing myocarditis.
- The immune response controls the parasites, but some persist in tissues.
- Persistent parasites and autoimmune reactions maintain low-grade inflammation for years.
- Myocytes, autonomic neurons and small vessels are lost; fibrosis replaces them.
- Fibrosis disrupts conduction, thins the apex and dilates the ventricles: arrhythmia, aneurysm, thrombus and failure.
Clinical notes
- Screening of blood donors, pregnant women and people from endemic regions with serology is key; treatment with antiparasitic drugs is most effective in the acute phase and in children.
- Chagas cardiomyopathy has a worse prognosis than other dilated cardiomyopathies.
Test yourself
Think of the answer, then tap the question to see it.
What characteristic ventricular lesion is seen in chronic Chagas cardiomyopathy?
An apical aneurysm of the left ventricle, often containing mural thrombus.
Which conduction pattern is typical?
Right bundle branch block with left anterior fascicular block, plus AV block and ventricular arrhythmias.
Why are parasites rarely seen in chronic Chagas heart disease?
The chronic damage is driven by low-level parasite persistence and the immune response, so few organisms remain visible in tissue.
Connections
Microorganisms1
Educational content on the mechanisms of disease; not a diagnostic or treatment guide and no substitute for a health professional's advice. No doses are given.
Sources: Chagas disease (also known as American trypanosomiasis) (World Health Organization, 2025); Prevalence of Chagas disease in Colombia: A systematic review and meta-analysis (PloS one, 2019).
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Representative model, for educational purposes only.