text: An<unk>  is a device which is implanted in the heart of patients who suffer from<unk> lar diseases in their heart. When one or two of the four heart<unk> s of the heart have a malfunction, the choice is normally to replace the natural<unk>  with an<unk><unk> . This requires open-heart surgery.<unk> s are integral to the normal physiological functioning of the human heart. Natural heart<unk> s are structures which have evolved a form which meets their functional requirements, which is to induce largely unidirectional flow through themselves. Natural heart<unk> s may become dysfunctional due to a variety of pathological causes. Certain heart<unk>  pathologies may necessitate the complete surgical replacement of the natural heart<unk> s with heart<unk>  prostheses.
option_0: Artificial heart valve
option_1: Heart transplantation surgical procedure
option_2: Myocarditis surgery
option_3: Endocarditis surgery
option_4: Cardiomyopathy surgery
option_5: Right heart failure surgery
option_6: Atrioventricular block surgery
option_7: Valvular heart disease surgery