The process starts with atherosclerosis, progresses through inflammation to yield an active unstable plaque, which undergoes thrombosis and results in acute myocardial ischemia, which, if not reversed, results in cell necrosis (infarction). Studies show that 64% of all unstable anginas occur between 22:00 and 08:00 when patients are at rest.In stable angina, the developing atheroma is protected with a fibrous cap. This cap may rupture in unstable angina, allowing blood clots to precipitate and further decrease the area of the coronary vessels lumen. This explains why, in many cases, unstable angina develops independently of activity. Microvascular angina
Microvascular angina, also known as cardiac syndrome X, is characterized by angina-like chest pain, in the context of normal epicardial coronary arteries (the largest vessels on the surface of the heart, prior to significant branching) on angiography. The original definition of cardiac syndrome X also mandated that ischemic changes on exercise (despite normal coronary arteries) were displayed, as shown on cardiac stress tests. The primary cause of microvascular angina is unknown, but factors apparently involved are endothelial dysfunction and reduced flow (perhaps due to spasm) in the tiny "resistance" blood vessels of the heart. Since microvascular angina is not characterized by major arterial blockages, it is harder to recognize and diagnose. Microvascular angina was previously considered a rather benign condition, but more recent data has changed this attitude.
Beta blockers, specifically B1 adrenergic blockers without intrinsic sympathomimetic activity are the most preferred for the angina treatment out of B1 selective and non-selective as well as B1 ISA agents. B1 blockers are cardioselective blocking agents such as Nevibolol, Atenolol, Metoprolol and Bisoprolol, which result in blocking cAMP in the heart muscle cells. The cAMP which plays a vital role in phosphorylating the ryanodine receptor and LTCC will usually increase Ca+2 levels in the heart muscle cells, which will then result in contraction is blocked. Therefore, B1 blockade decreases the HR and contraction of the heart muscle, making it need less oxygen demand. An important thing to note is that the B1 cardioselective blockers are cardioselective and not cardio specific. This means that if the beta-adrenergic antagonist is prescribed in higher doses, it can lose the selectivity aspect and begin causing hypertension from B2 adrenergic stimulation of smooth muscle cells. This is why in therapy for patients with angina, the vasodilatory organonitrates complement the use of B-blockers when prescribed the use of angina. The preference for Beta-1 cardioselective blockers is for B1 cardioselective blockers without instrinsic sympathetic activity. Beta blockers with intrinsic sympathetic activity will still do the beta blockade of the heart muscle cells and have a decreased ionotrophic and chronotropic effect, but this effect will be to a lesser extent than if the beta blocker did not have the instrinsic sympathetic activity. A common beta-blocker with ISA prescribed for the treatment of angina is Acebutolol.