Angina is classified in many ways .The most useful; clinical classification is stable and unstable angina .
While ,the former generally is considered innocuous the later conveys a sinister signal to the patient and the physician.
Why stable angina is stable ?
In stable angina
The patient knows how the pain is going to behave by his past experience.
Very predictable .The patient knows at what distance it’s going to come
He also knows when it will disappear.(For some , with rest for others with nitrates)
He also knows where the chest pain will radiate.
If some thing is unusual it is unlikely to be stable angina , also any first episode of angina is considered unstable as one wouldn’t know how the angina is going to behave !
How is that stable angina has such a learned behaviour ?
The main reason for the beningn nature of stable angina is the coronary artery has “stable plaques”
Stable plaques produce stable angina ,Unstable plaques cause unstable angina
Stable plaque s restrict blood flow only at times of increased demand( ie supply side ischemia.) There is no thrombus in these plaques.As soon as the exertion ends the angina is relieved.So in chronic stable angina, the patient is stable, the angina is stable , the palque is stable , the coronary blood flow is stable.
Unstable palques have erosion and thrombus , and it interferes with blood flow even at rest .So in unstable angina, not only the angina is unstable , the plaque is unstable ,coronary blood flow is unstable. So it is obvious unstable angina , may not be relieved by bed rest.It needs intensive treatment.
Is there a overlap between stable and unstable angina?