A 34-year-old agricultural worker from rural Bolivia has 2 years of progressive exertional dyspnea. Examination shows a third heart sound, displaced apex, and irregular pulse due to atrial fibrillation. Echocardiogram shows a dilated left ventricle with a distinctive apical aneurysm containing mural thrombus. He reports chronic constipation and difficulty swallowing. What is the most likely etiologic agent?

• A Toxoplasma gondii
• B Trypanosoma cruzi ✓
• C Coxsackievirus B
• D Schistosoma mansoni

Explanation

Chronic Chagas cardiomyopathy, caused by Trypanosoma cruzi, is characterised by biventricular dilation, apical aneurysm with mural thrombus, atrial fibrillation and bundle branch blocks, accompanied by gastrointestinal mega-syndromes (megacolon, megaesophagus) from autonomic denervation. Coxsackievirus A causes acute lymphocytic myocarditis without apical aneurysm. Toxoplasma myocarditis occurs in the immunosuppressed. Schistosomiasis causes cor pulmonale via pulmonary hypertension, not an apical aneurysm. Diagnosis rests on serology, and treatment is benznidazole.

Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.