Chagas disease, which is caused by the parasite
Trypanosoma cruzi
, is an important cause of heart failure. We investigated modifications in the cellular electrophysiological and calcium-handling characteristics of an infected mouse heart during the chronic phase of the disease. The patch-clamp technique was used to record action potentials (APs) and L-type Ca
2+ and transient outward K
+ currents. [Ca
2+]
i changes were determined using confocal microscopy. Infected ventricular cells showed prolonged APs, reduced transient outward K
+ and L-type Ca
2+ currents and reduced Ca
2+ release from the sarcoplasmic reticulum. Thus, the chronic phase of Chagas disease is characterised by cardiomyocyte dysfunction, which could lead to heart failure.