There are 4 principle mechanisms that i can think of (there may be more than this): (1) ischemia
- where the heart muscle dies because the oxygen supply to the heart is cut off by blockage in the coronary artery
or a person has stopped breathing; (2) fibrillation
- where the electric impulses to the different heart chambers get out of sequence and circulation is disrupted; (3) electrolyte imbalance
that impedes the heart muscle's ability to contract or relax; and (4) loss of nerve signals to the heart from the lower brain stem.