- Classically associate with a prolonged asymptomatic period followed by rapid progression of symptoms
- Asymptomatic disease:
- Risk of sudden death of 1%
- Symptomatic disease:
- Poor prognosis without valve replacement
- Average survival 2-5 years
- 50% incidence of sudden death and a monthly mortality of 2%
- Asymptomatic disease:
- There is no definitive evidence that medical treatment alone can slow disease progression