A patient with sudden cardiac irregularities and amastigotes in myocardium most likely suffered from?

The presence of sudden cardiac irregularities alongside amastigotes found in the myocardium strongly indicates the involvement of Trypanosoma cruzi, the causative agent of Chagas disease. This parasitic infection is notable for its acute and chronic phases, where damage to cardiac tissue can lead to severe arrhythmias and other cardiac complications.

In Chagas disease, the amastigotes typically form pseudocysts within the heart muscle, leading to myocarditis. This can result in symptoms such as palpitations, irregular heart rhythms, and even heart failure as the disease progresses. The identification of these intracellular forms in the myocardium is a key diagnostic feature that helps differentiate Chagas disease from other parasitic infections.

While other options mention Leishmania and Trypanosoma species, they do not align with the symptoms presented. Leishmaniasis primarily affects the skin, liver, and spleen, not the myocardium, and it's caused by different Leishmania species, none of which are associated with cardiac irregularities in this manner. On the other hand, Trypanosoma gambiense is implicated in African sleeping sickness and does not involve amastigotes in the myocardium or cause the related cardiac symptoms seen in Chagas disease