Cardio 2 Flashcards
what causes atrioventricular junctional tachycardias?
re-entry circuits - two separate pathways for impulse conduction
what is the enzyme that breaks down bradykinin?
angiotensin converting enzyme - excess bradykinin (since it’s not being broken down) is the reason why some patients on ACEi get a persistent dry cough
explain how ACE inhibitors work
ACE inhibitors inhibit conversion of angiotensin I to angiotensin II in the lungs - this prevents it from acting on the adrenals to increase aldosterone secretion and thus cause water and sodium retention at the kidneys.
angiotensin II is also a vasoconstrictor, so ACEi act as vasodilator, and causes sodium and water excretion - lower blood volume, lowers BP.
how do angiotensin receptor blockers produce a similar effect to ACEi? give two examples of ARBs
by blocking angiotensin II receptors, so its actions cannot be exerted.
losartan, candesartan.
give 2 examples of ACEis
ramipril, lisinopril
why do you get hyperkalaema as a side effect of angiotensin 2 receptor blockers?
ARBs cause a direct effect on aldosterone production in the adrenals - aldosterone works on the distal convoluted tubules of kidney by causing sodium to be reabsorbed in return for potassium excretion - ARBs reverse this transfer, so there’s potassium retention.
calcium channel blockers are negatively inotropic and negatively chronotropic, what does this mean?
inotropic - reduces the contraction.
chronotropic - lowers the heart rate.
how do calcium channel blockers work? give some examples.
decrease calcium entry into vascular and cardiac cells. intracellular calcium is lower - relaxation and vasodilation of arterial smooth muscle.
reduce myocardial contractility and suppress cardiac conduction, particularly at AV node.
this reduces myocardial oxygen demand - important in angina.
dihydropyridines (amlodipine, nifedipine) - selective for vasculature.
non-dihydropyridines (diltiazem, verapamil)- selective for heart
what clotting factors does warfarin work on?
2, 7, 9, 10 by inhibiting vitamin K synthesis - so anticoagulates by inhibiting coagulation factor synthesis
statins are given to correct hyperlipidaemia, what enzyme do they act on? name 2 statins.
HMG-CoA reductase - involved in making cholesterol.
so they reduce the cholesterol production in liver and increase clearance of LDL-cholesterol from blood.
simvastatin, atorvastatin, pravastatin.
if you have a patient that comes in with unstable angina but tells you he is allergic to aspirin, what is then your first line of treatment after giving GTN?
clopidogrel monotherapy
give an example of a short and a long acting nitrate
short - glyceryl trinitrate (GTN).
long - isosorbide mononitrate
how do nitrates work to reduce the pain of angina?
converted to NO, which is a vasodilator - relaxation of capaticance vessels reduces cardiac preload + LV filling, which reduces cardiac work and myocardial oxygen demand.
give 2 possible side effects of nitrates
flushing, headaches, light headedness, hypotension
name 3 beta blockers
bisoprolol, atenolol, propranolol, metoprolol
how do beta blockers work to improve symptoms of ischaemic heart disease?
they reduce force of contraction and speed of conduction in the heart via beta 1 receptors - reducing cardiac work and oxygen demand.
how do beta blockers work as a treatment for AF?
slow the ventricular rate by prolonging the refractory period at the AV node
list the indications for beta blockers
IHD - symptoms and improve prognosis.
chronic heart failure.
AF and other SVTs - reduce rate, maintain sinus rhythm.
hypertension - only if other medicines are insufficient.
how do beta blockers work as a treatment for hypertension?
reduce renin secretion from the kidney, which is mediated by beta1 receptors.
give some possible SEs of beta blockers
fatigue, cold extremities, headache, nausea, sleep disturbance, ED in men.
name an aldosterone antagonist
spironolactone, epleronone
what cardiac indication do aldosterone antagonists treat?
chronic heart failure - as an addition to beta blocker and ACEi/ARB
how do LMWHs work?
inhibit factor Xa by inhibiting antithrombin
how does fondaparinux work?
inhibits factor Xa.
how does aspirin work in prevention of thrombosis?
it irreversibly inhibits cyclooxygenase (COX) to reduce production of pro-aggregation factor thromboxane from arachidonic acid - reduces platelet aggregation and risk of arterial occlusion.
give some examples of antiplatelet drugs, apart from aspirin
clopidogrel, new oral anticoagulants, glycoprotein IIb/IIIa inhibitors
how does clopidogrel work?
prevents platelet aggregation by binding irreversibly to adenosine diphosphate receptors on surface of platelets
- independent of COX pathway, so can be taken with aspirin
how do glycoprotein IIb/IIIa inhibitors work?
prevent platelet aggregation by inhibiting the GPIIb/IIIa receptor on platelet surface
name 2 fibrinolytic (thrombolysis) drugs
alteplase, streptokinase
how do fibrinolytic drugs work?
catalyse the conversion of plasminogen to plasmin which acts to dissolve fibrinous clots and re-canalise occluded vessels.
- allows reperfusion of tissues, preventing/limiting tissue infarction.
name a loop diuretic
furosemide, bumetanide
give a cardiac indication of loop diuretics
symptomatic treatment of fluid overload in chronic heart failure
describe the mechanism of loop diuretics
act on ascending limb of loop of Henle to inhibit the Na/K/2CL cotransporter that transports the ions into the cell - water follows these ions, so they have a potent diuretic effect.
also - cause dilation of capaticance vessels - reduces preload + improves contractile function of the heart.
what are potassium sparing diuretics used for? name an example.
used as part of combination therapy, to treat hypokalaemia arising from loop/thiazide diuretic use.
amiloride.
how do potassium sparing diuretics work?
weak diuretics.
act on distal convoluted tubules in kidney - inhibit sodium and water reabsorption by acting on epithelial sodium channels - causes potassium retention.
give an example of a thiazide/thiazide like diuretic
bendroflumethiazide, indapamide, chlortalidone
describe the mechanism of action of thiazide diuretics
inhibit the Na/Cl cotransporter in the distal convoluted tubule of the nephron, preventing reabsorption of sodium and water.
also cause vasodilation.
for what cardiac problem might sildenafil be prescribed? what class of drug is this?
primary pulmonary hypertension.
phosphodiesterase type 5 (PDE5) inhibitor
how does sildenafil work as a treatment of pulmonary hypertension?
causes arterial vasodilation by increasing cGMP (normally broken down by PDE5).
