Re: Unstable angina
Stable angina is pain brought about by known activities (predictable) such as if I were to say "everytime I run fast, I get angina in my left arm again." As the disease progresses, then you can develop unstable angina, which means you still angina upon exertion, but now it comes and goes at rest. True, that is when it gets dangerous.
You said that you get the pain in your chest, but it gets better when you sit up. Good news is that angina does not disappear from movement like that. If anything, an increase in heartrate will place more demand on the heart muscle, leading to a demand for more oxygen while the flow in the coronary arteries will be limited. Net result is increased angina.