Lecture 10 - Angina Flashcards
what is ischaemia?
an insufficiency in blood supply. the coronary arteries are the only source of blood for the heart muscle
what is angina?
if coronary arteries are blocked the blood supply to the heart will reduce, which may result in chest pain
what is angina pectoris?
the result of an ischemia caused by an imbalance between myocardial blood supply and oxygen demand
when is angina pectoris typically presented in people with and who is it more common with?
coronary artery disease and more common in women than in men
what may angina occur by?
atherosclerosis with blood clot
atherosclerosis
spasm
what is stable angina?
occurs when coronary perfusion is impaired by fixed or stable atheroma of coronary arteries
what is unstable angina?
is characterised by rapidly worsening chest pain on minimal exertion or at rest
what is unstable angina associated with?
associated with an ulcerated atheroma and thrombus formation. this produces reduction of coronary blood flow to produce angina at rest
describe prinzmetals angina - what does it cause
coronary spasm:sudden involuntary contraction of smooth muscle tissue or coronary artery
what does the spasm do?
spasm temporarily narrows the coronary artery
what does the spasm in prinzmetals angina cause?
causes transient impairment of coronary blood supply
when does prinzmetals angina occur?
usually occurs at rest
majority of patients have an atherosclerotic plaque but this is often minor when compared with the extent of pain
long term prognosis is very good
what are the classifications of stable angina?
exertion angina
angibnal equivalent syndorme
syndrome x
silent ischameia
decubitus angina
nocturnal angina
what does exertion or classical angina arise from?
an increase in myocardial oxygen demand during exertion or emotion. relief occurs by rest and nitroglycerine
coronary artery obstructions are not sufficient to result in resting myocardial ischaemia
what is anginal equivalent syndrome cause d by and what are the symptoms?
caused by myocardial ischema
symptoms: shortness of breath or pain at a site other than the chest eg arm or jaw
describe syndrome X angina
typical, exertion angina with positive exercise stress test
anatomically normal coronary arteries
reduced capacity of vasodilation in microvasculature
long term prognosis is very good
describe silent ischemia
very common
more episodes of silent than painful ischemia in the same patient
difficult to diagnose
- holter monitor (records heart rate and rhythm over a 24 hour period)
- exercise testing
describe debuticus angina
chest pain occurs only while lying down
- relived by standing or sitting
usually associated with impaired left ventricular function
the patient usually has severe coronary artery disease
describe is nocturnal angina
it awakes the patient from sleep
it may be provoked by vivid dreams
it may occur due to coronary spasm
what is used in stable angina assessment ?
history: grading scale
exercise testing
electrocardiogram
what are the classes of angina severity by the Canadian cardiovascular society graded as?
class I: angina only during strenuous or prolonged physical activity
class II: slight limitation, with angina only during vigour’s physical activity
class III: moderate limitation, symptoms with everyday living activities
Class IV: severe limitation, inability to perform any activity without angina or angina at rest
what is the goal of stable angina excercises testing?
to induce a controlled, temporary ischemic state during clinical and ECG observation
what is the goal of stable angina excercise testing?
to induce a controlled, temporary ischemic state during clinical and ECG observation
what is seen in an ECG with ischemia in the graph?
ST segment depression occurs with ischemia and reverses after ischemia disappears
what is an ECG like between angina attacks?
the resting ECG may be normal between angina attacks (unless there are other problems such as myocardial infarction heart block or left ventricular hypertrophy)
what is unstable angina in testing like?
angina at rest not responding readily to therapy
recent onset is - less than 1 month
increase in frequency and duration of episode
may be serious indicator of an impending heart attack
describe the summary of atherosclerotic plaque and thrombus
- initially fatty streak
- plaque enlarges
- loss of endothelium and exposure of collagen
- platelet adherence and activation
- fibrin meshwork deposition with RBC entrapment
- more flow turbulence, more platelet adherence, more fibrin deposition
- thrombus of alternating layers of platelets, fibrin and red blood cells
why do plaques rupture?
risk of plaque rupture depends on plaque type rather than plaque size. plaques rich in soft extracellular lipids are vulnerable (rupture-prone).
presence of smooth muscle cells in the fibrous cap may provide resistance to rupture.
extracellular lipid accumulation and cap weakening predispose the plaque to rupture
describe the alleviation of angina symptoms and treatment
beta blockers first line therapy
- inadequate control of symptoms - add a calcium channel blocker
if intolerant of beta blockers, treat with a rate limiting calcium channel blocker, long acting nitrates or nicorandil
sublingual gum tablets or spray for immediate relief and before activities known to bring on angina.
referral to a cardiologist of symptoms not controlled on maximum therapeutic doses of two drugs
what do these beta blockers drugs do?
lower the oxygen demand of the heart by affecting blood pressure, venous return, heart rate and contractility
what drugs are used for the treatment of stable angina?
beta adrenergic receptor blockers
calcium channel blockers
nitrates
potassium channel activators
describe what beta adrenegeric receptor blockers od and give examples of them
beta adrenergic receptor blockers eg atenolol, bisoprolol and metoprolol
beta adrenergic blocking agents decrease the oxygen demands of the myocardium by lowering both the rate and force of contraction of the heart
describe how calcium channel blockers work and give examples of them
the blockers prevent entry via L type calcium channels
calcium influx is increased in ischemia because of the membrane depolarisation that hypoxia produces. calcium channels blockers protect the tissue by inhibiting the entrance of calcium int cardiac and smooth muscle cells of the coronary and systemic arterial beds.
examples are diltiziam and verapamil
describe how nitrates work in producing stable angina and give examples of them.
nitrates relax coronary arteries by decreasing coronary vasconstriction or spasm and increase perfusion of the myocardium. ind addition they relax veins, decreasing preload and myocardial oxygen consumption
nitrates donate nitric oxide which stimulates cyclic guanosine monophosphate cyclase that can release calcium in muscle.
examples are gtn; isosorbide mononitrate
describe how potassium channel activators work in treatment to give stable angina
potassium channel activators are nicorandil
nicrorandil has the dual properties of a nitrate and K+ ATP channel agonist. activation of K+ ATP channels on smooth muscle cells hyper polarises the membrane and decreases calcium entry
