![]() In most cases, formation of labile nonocclusive thrombi at the site of a fissured or ulcerated plaque is the mechanism for reduction in flow. Unstable angina is caused by episodes of increased epicardial coronary artery tone or small platelet clots occurring in the vicinity of an atherosclerotic plaque. In some patients, anginal symptoms may occur without any increase in myocardial oxygen demand but rather as a consequence of abrupt reduction in blood flow, as might result from coronary thrombosis (unstable angina) or vasospasm (variant or Prinzmetal angina). Since blood flow is inversely proportional to the fourth power of the artery's luminal radius, the progressive decrease in vessel radius that characterizes coronary atherosclerosis can impair coronary blood flow and lead to symptoms of angina when myocardial oxygen demand increases, as with exertion (so-called typical angina pectoris).This imbalance may be caused by an increase in myocardial oxygen demand (which is determined by heart rate, ventricular contractility, and ventricular wall tension) or by a decrease in myocardial oxygen supply (primarily determined by coronary blood flow but occasionally modified by the oxygen-carrying capacity of the blood) or sometimes by both. Angina pectoris, the primary symptom of ischemic heart disease, is caused by transient episodes of myocardial ischemia that are due to an imbalance in the myocardial oxygen supply-demand relationship.Nitrates + DHPs + β blockers: Supraaddative, Nitrates (↓preload ) + slow acting DHPs(↓Īfterload): valuable in severe variant anginaĭ. This leads to relaxationĪnd vasodilation. ![]() Muscle, which closes voltage-gated calcium channels andĭecreases intracellular calcium. Opening these channels hyperpolarizes the smooth MOA: Potassium-channel openers are drugs that activateĪTP-sensitive K+channels in vascular smooth muscle. Nifedipines) mayĪdditional beneficial effect in variant angina Effective in classical as well as variant anginaĪrteriolar dilation → ↓afterload →↓work load Selective beta blocker are preferred, taken Decrease frequency and severity of attack : Lower risk of sudden cardiac death in IHD patient Unstable angina and Myocardial Infarctionģ. long acting preparation of GTN or otherĢ. produce relief within 3 min if not it can be Sublingual GTN or Dinitrate is taken sos Last dose should be given in the afternoon Active metabolite of isosorbide dinitrate Last dose should not be given later than High and variable first pass metabolism SL for acute attack and oral for prophylaxis Can also be given transdermally or i.v. Sublingual spray act more rapidly than tab Given SL: acts within 1-2 min, t1/2= 2 min Volatile liquid: adsorbed on inert matrix of Dependence: so slow withdrawal with addition of Nitrate free interval is created every day toĮ. on continuous use (oral, transdermal, i.v.) Flushing, sweating, hypotension, palpitation, Ischaemia induce dilation of arterioles inīoth actions (a & b) preferentially increaseī. Nitrates preferentially relax bigger coronaryī. Dilates arteries → ↓ t.p.r → ↓ afterload →Ī. Dilates vein → ↑peripheral pooling of bloodī. Ischaemic areas via collaterals (Do not showĪ. Myosin light chain, resulting in vascular smooth ElevatedĬGMP ultimately leads to dephosphorylation of the Nitrite ions and then to nitric oxide, which, in turn,Īctivates guanylate cyclase and increases the cells’Ĭyclic guanosine monophosphate (cGMP). Smooth muscle by their intracellular conversion to Organic nitrates, such as nitroglycerin, relax vascular Preload and myocardial oxygen consumption. Nitrates relax the veins (venodilation), decreasing Spasm, increasing perfusion of the myocardium and, MOA: Nitrates inhibit coronary vasoconstriction or Long acting: Isosorbide dinitrete (orally),Īll share same action differ in time course Short acting: Glyceryl trinitrate (GTN,ī. ![]() To coronary vasodilators, such as nitroglycerin andĪ. Prinzmetal angina generally responds promptly The heart muscle from the spasm of the coronary Symptoms are caused by decreased blood flow to Prinzmetal angina is an uncommon pattern ofĮpisodic angina that occurs at rest and is due to Angina: a strangling Pectoris: of the chestĪdverse oxygen supply & demand in portion
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