Hello dear, thanks for your question on HCM. I can understand your situation and problem. Amyloidosis is slowly growing, chronic infiltrating disease. In this disease amyloid (protein substance) accumulates in almost all organs of the body. But the common organs are 1. Liver 2. Heart 3. Brain 4. Kidneys. In heart it usually affects conduction system. So this can cause sudden stoppage of heart and sudden cardiac death due to cardiac arrest. Another possibility is brain involvement. If amyloid involve certain vital areas of brain like pons and medulla where all vital functions like respiration, blood pressure, pulse etc are controlled than sudden death can be seen. So cardiac or brain involvement is the common cause for sudden death in amyloid patients.