**Overview**: This study is for people with a condition called autonomic failure, where they have problems controlling blood pressure. This often causes very low blood pressure when standing (orthostatic hypotension) and high blood pressure when lying down (supine hypertension). The study aims to see if applying heat to the stomach at night can help lower high blood pressure while lying down. **Key Points**: - The study includes adults aged 18-80 with autonomic failure and high blood pressure while lying down. - It involves applying heat to the abdomen during the night and comparing it with no treatment. - Participants need to be able to give informed consent and cannot have certain health conditions like heart or liver problems. **Details**: *Autonomic failure* means the body's automatic processes, like controlling blood pressure, don't work well. *Supine hypertension* is when blood pressure is too high when lying flat. Applying heat might help lower blood pressure by improving blood flow. This study will compare the effects of heat with a control group where no heat is applied. Participants will need to spend the night in a research facility for testing and must be willing to follow study rules.