We all know,narrowing of coronary artery by an atheromatous plaque causes angina.
upto 70% narrowing,patients remain asymptomatic,because of vasodilator reserve.
here are few different types of angina,
when narrowing exceeds 70%,patients experience angina,due to loss of the vasodilator reserve and extra demand by the exerting heart.This is usually relieved by rest.
when the exertional angina pattern is constantly present for a period of >2months,its called stable angina.
The constantness should be related to the following features of angina-
a)amount of exertion producing angina
b)response to rest
c)severity of angina
3 types of unstable angina are defined-
New onset angina,less than 2months duration,severe with frequency more than/equal to 3 episodes per day.
the change of pattern of previously existing c/c stable angina,viz,increase severity of pain,less effort precipitating pain or inadequate response to rest or medications.
when the narrowing of the arterial lumen reaches 90-95%,the patient experiences pain at rest.
also known as vasospastic angina,occurs not due to the usual thrombosis of the coronary arteries,but due to the vasospasm,esp of the epicardial arteries.
ECG changes are similar to hyperacute infarcts,with ST elevation and tall T waves.
But these do not evolve serially,as an otherwise infarct pattern wud do.
rather it settles down rapidly,and Q waves never appear.
cardiac enzymes in the serum are NOT elevated,as there is no myocardial necrosis.
this type of angina has excellent prognosis,though sumtimes sudden death might occur.
5)FIXED THRESHOLD ANGINA:
in this the threshold,ie the amount of exertion precipitating the angina remains same thruout the course of the disease.
combination of fixed narrowing with superadded vasospasm is known as mixed angina.