Cardiovascular Flashcards
What are the various cardiac stimulant classes?
beta 1 agonists, phosphodiesterase inhibtors, glucagon, and calcium salts.
What beta 1 agonist can be used to increase renal perfusion and GFR, at a low dose?
dopamine.
What are the effects of dopamine at a high dose?
vasoconstriction.
What is the drug of choice to treat sinus bradycardia, or incomplete AV block?
atropine.
What is the most likely cause of atropine not working when treating an incomplete AV block? What drug would you use instead?
It is a complete AV block if atropine doesn’t work. Use epinephrine instead.
Why is epinephrine contraindicated in incomplete AV blocks?
because it can cause tachycardia and lead to death.
If a patient has low BP, what would be the course of action? What two drugs would you avoid and why?
for low bp: give fluids and a vasoconstrictor, epi being drug of choice. Avoid phenylephrine or norepi b/c of the risk of reflexive bradycardia.
What is the result of severe heart failure?
pulmonary edema due to Na+ retention and stimulation of aldosterone.
What are the 2 therapies involved in treating congestive heart failure?
non drug therapy (restricted salt intake and exercise) as well as drug therapy.
What are the two classes of positive inotropic drugs used in treatment of CHF?
digitalis glycosides and beta 1 agonists.
What is the most commonly used digitalis glycoside? Is it still used today? Why or why not?
Digoxin. It isn’t used anymore because it’s not very safe. Has a narrow safety margin and can cause tachycardia/tachyarrhythmia
What drug has replaced digoxin?
pimobendin.
what are the 3 digitalis glycosides?
digitoxin, digoxin, and ouabain.
What is the MOA of digoxin?
inhibits Na+/K+ ATPase in the myocardial cell membrane, which increases the amount of Na+ available to exchange with Ca+. This causes an increase in intracellular calcium, thus increasing contractility.
What is the main cardiovascular effect of Digoxin? What is another effect of this drug on the heart?
positive inotropic effect. Increases the mechanical efficiency of the failing heart, without increased myocardial oxygen demand.
What is the goal when using digoxin?
normalization of blood pressure and peripheral resistance.
T/F: digoxin is good at treating edema due to CHF due to its diuretic effect.
True. This effect is secondary to increased cardiac output.
T/F: digoxin can be administered IV in case of ER.
True, but has to be administered slowly.
How is digoxin excreted in cats?
In cats, excretion is renal and hepatic. It is excreted in the bile.
What type of arrhythmias is digoxin used to treat? In what species?
supraventricular arrhythmias only in dogs.
What medication is used to treat digoxin toxicity?
cholestyramine
What beta 1 agonists are used to treat heart failure and when are they used?
dopamine and dobutamine. They are only used once by injection in severe cases.
What drugs are inodilators?
pimobendan, inamrinone, and milrinone
Why is pimobendan recommended over digoxin?
Wider safety margin and less likely to cause tachycardia.
When would you use inamrinone and milrinone?
as adjunctive therapy in severe cases of heart failure.
Why is pimobendan considered a balanced vasodilator?
Because it dilates both arteries and veins.
What is the MOA of pimobendan?
it sensitizes the cardiac contractile apparatus to calcium by enhancing interaction between calcium and troponin C complex. It doesn’t primarily increase intracellular calcium.
When is pimobendan contraindicated?
in hypertrophic cardiomyopathy and where an increase of cardiac output is not physically possible.
T/F: inamrinon and milrinone can be used for long term use.
False. They are arrhythmogenic and can not be used long term.
What is the best vasodilator to treat CHF?
ace inhibitors, because you get RAS stimulation. Beta blockers are good too because you get sympathetic stimulation.
Is prazosin used as a vasodilator for CHF?
no.
What diuretics are used in CHF?
loop diuretics, thiazide diuretics, and potassium sparing diuretics.
In what cases are beta blockers used in CHF and what do they do?
They are only used in mild or moderate cases of CHF. They blunt the adverse cardiovascular effects of the sympathetic.
What is the mode of action of carvedilol?
It is a non-selective beta-blocker and alpha 1 blocker. It inhibits endothelin release.
T/F: beta-blockers can increase serum potassium?
True.
What other drugs can be used in patients dying from heart failure?
oxygen therapy, morphine sulfate, aminophylline, and nebulization of ethanol (20%)
What type of arrhythmia leads to death? Why?
ventricular arrhythmia. Because they trigger ventricular fibrillation.
Can hypoxemia cause arrythmias?
yes.
What effect do class I B drugs have on action potential?
they shorten the duration of action potential.
Which class I Sodium channel blocker has no effect on action potential?
Class I C
T/F: Class I A drugs lengthen the action potential.
True.
What class I A drug is the drug of choice to treat atrial fibrilation in equines and ventricular arrhythmias?
quinidine
What drug is the drug of choice to treat ventricular tachycardia and tachyarrhythmia in dogs?
lidocaine IV.
In what animal are class IB drugs more commonly used?
In cats, with the exception of lidocaine.
What drug treats arrhythmias caused by digitalis?
Phenytoin.
What are class IC drugs used for?
They are used by cardiologists to treat refractory tachycardia. They are very arrhythmogenic.
Class II drugs are also known as ____.
Beta blockers.
Which class II drug is the prototype for non selective blockers?
propranolol
Which class II drug is the prototype for beta-1 selective blocker?
atenolol
Class II drugs treat what type of arrhythmias and are used in what animal?
treat supraventricular and ventricular tachyarrhythmias. They are used in cats.
Which drug is a non selective beta blocker that acts as a class III drug on the heart?
sotalol
T/F: verapamil and diltiazem act against both ventricular and supraventricular arrhythmias.
False. They only act against supraventricular.
What are the only 2 calcium channel blockers with anti-arrhythmic effects?
verapamil and diltiazem
Which are better, calcium channel blockers or beta blockers?
calcium channel blockers.
T/F: calcium channel blockers are contraindicated in CHF.
True.
Wha is the drug of choice for supraventricular and ventricular tachyarrhythmias is cats?
beta blockers
What antiarrhythmic drugs are used for bradyarrhythmias?
atropine, isoproterenol, and epinephrine.
What drugs are used to treat second-degree AV blocks?
atropine, isoproterenol, and glucagon.
Which drugs that act on blood vessels are used as decongestants? What problems can arise from these?
vasoconstrictors. They lose effect (tachyphylaxis) when used for a long time.
What else are vasoconstrictors used for?
vasodilatory hypotension.
epineprhine and norepinephrine are (selective/nonselective) alpha (agonists/antagonists)
nonselective, agonists
phenylephrine is a (selective/nonselective) alpha 1 (agonist/antagonist)
selective, agonist
How do beta blockers cause vasodilation?
indirectly by inhibiting renin.
Phenoxybenzamine is a sympatholytic vasodilator that is the drug of choice to treat what?
hypertension due to pheochromocytoma.
Which sympatholytic vasodilators are used in emergency hypertension?
non-selective alpha blockers.
Why can angiotensin converting enzyme inhibitors (ACE inhibitors) be used to treat early-severe heart failure?
Because they don’t have a negative inotropic effect.
Which ACE inhibitor is the only one approved in animals in the US?
enalapril
Which ACE inhibitor is the only one approved in animals in CAN?
Benazepril
T/F: ACE inhibitors can be given IV in case of emergencies.
False. Only given orally.
What does renin cleave to make angiotensin I? What inhibits renin?
angiotensinogen, blocked by beta blockers
ACE is also known as what? What 2 things does it break down and what are the end results?
ACE is also known as kininase. It breaks down angiotensin I, resulting in angiontensin II, and it breaks down bradykinin, inactivating it.
What is the MOA of ace inhibitors?
inhibit angiotensin converting enzyme, thus inhibiting the synthesis of angiotensin II.
Why do you worry about the kidneys when you lower blood pressure?
because of decreased GFR.
What is the drug of choice to treat hypertension in dogs?
ACE inhibitors
T/F: ACE inhibitors increase blood perfusion to the kidneys.
True. They only decrease GFR.
Which is the most effective ACE inhibitor?
benazepril. 50% excreted in bile, 50% in urine.
T/F: enalapril can be administered orally and parenterally
true.
What are 2 direct-acting vasodilators?
hydralazine and nitrates
What is hydralazines MOA?
increases local concentrations of PGI2 (vasodilator). It also may inhibit calcium influx into smooth muscles of arteries.
What is the MOA of nitrates?
formation of the reactive radical NO, which activates guanylyl cyclase, increases cyclic GMP and stimulates GMP-dependent protein kinase
direct acting vasodilators usually act on the receptors found where?
blood vessels.
What are the drugs that fall under the class calcium channel blockers?
verapamil, diltiazem, amlodipine, and nifedipine.
What happens if you block calcium channels in the heart?
you get an antiarrhytmic effect. Only a supraventricular effect (except for amlodipine or nifedipine)
T/F: all calcium channel blockers are vasodilators and anti-hypertension
True.
What is the drug of choice for hypertension in cats?
amlodipine.
aside from calcium channel blockers, what other class of drugs decrease afterload and pre-load?
ACE inhibitors.
What drug do you use on a hyperthyroid and hypertensive cat?
beta blocker.
What is the drug of choice for myocardial hypertrophy in cats?
diltiazem.
What are some adverse effects of CCBs?
bradycardia and AV block, hypotension, GI effects, and elevated liver enzymes (temporary).
What are some anti-hypertensive drugs?
diuretics, beta blockers, vasodilators, and calcium channel blockers.
