Papillary muscles are conic parts of the heart muscle, reaching into the ventricle and are connected to the valves with the Chordae tendineae. In the right ventricle there are three, in the left one two papillary muscles.
Cardial contraction takes places at the beginning of the systolic period in the chamber. They put tension to the valves and prevent them from flapping into the atrium during the systolic period.
In a myocardial infarction, a tear in the papillary muscle can take place, mainly in the left ventricle. It can lead to acute mitral valve insufficiency or prolaps of the mitral valve. If the papillary muscles of the right ventricle are affected, it may lead to tricuspidal insufficiency.
Image source: E. Faccio, P. Saccheri