Disturbances of the fetal heart rate have been successfully treated in utero with various medications including digoxin and other anti-arrhythmic agents administered to the mother. Although placental transfer can be unreliable, therapeutic levels of these agents can be achieved in the fetus and their effects can be monitored in the fetus using ultrasound.
The fetal heart rate and rhythm can be visualised using Doppler ultrasound.
Evidence of heart failure can be seen as fluid build up in body cavities (eg. the abdomen).