Cardio: Drugs affecting HR + Force Flashcards
HCN channels mediate the funny current. Which drug acts on these channels?
Ivabradine
What affect does blocking HCN channels have on the slope of the pacemaker potential and thus the HR?
Decreases slope of the pacemaker potential and so decreases HR
What are the clinical uses for Ivabradine?
Angina
Heart failure
Which drugs are examples of Beta adrenoreceptor agonists?
Adrenaline
Dobutamine
What affects do beta adrenorecptor agonists have on the heart?
Increase HR + force of contrition (Positive inotropic + chronotropic effect)
Increase cardiac output
Redistribute blood flow to the heart
When is adrenaline used clinically?
IM in anaphylactic shock
IV in cardiac arrest
When is dobutamine used clinically?
In acute but potentially reversible heart failure (e.g. due to shock/after surgery)
Which beta adrenoreceptor antagonists are selective for B1 receptors?
Atenolol
Bisoprolol
Metoprolol
What effects do B1 adrenoreceptor antagonists have on the heart?
Slow HR by delaying conduction through AV node
Increase duration of diastole
Decrease sympathetic activity
Which drug is non-selective for B1 and B2 adrenoreceptors?
Propanolol
What are the clinical uses of beta-blockers?
1) Angina - slows HR + reduces demand on the heart
2) AF + SVT’s - decrease excess sympathetic drive + help restore normal sinus rhythm
3) Heart failure
4) Hypertension
List the 6 main side effects of beta-blockers
1) Bronchospasm
2) Cold peripheries
3) Hypoglycaemia
4) Fatigue
5) Aggravation of HF
6) Bradycardia
Which drug is a non selective antagonist of muscarinic receptors?
Atropine
What effect does atropine have on the heart?
Increases HR, has no affect on BP
What is atropine used to treat?
Bradycardia
What dose of atropine must be given in order to prevent HR decreasing further?
No less than 300 micrograms
What type of drug is digoxin?
A positive inotrope (Increases contractility)
A negative chronotrope (Decreases HR)
Where does digoxin bind?
The alpha subunit of Na+/K+ ATPase in competition with K+
How does digoxin affect vagal activity?
Increases it - slows SA node discharge, slows AVN conduction + increases refractory period
What are the clinical uses of digoxin?
Used to slow rapid AF
Used in HF where all other treatments are ineffective
Which body state can dangerously enhance the effects of digoxin?
Hypokalaemia
What are the adverse effects of digoxin?
Arrhythmia
Toxicity - yellow vision + nausea
Which drug reverses digoxin toxicity?
Digiband
What affect to calcium channel antagonists have on the heart?
Prevent opening of L-type calcium channels in the heart + smooth muscle to decrease Ca entry
This slows HR
Which calcium channel antagonist is selective for smooth muscle?
Amlodipine (dihydropiridine)
Which calcium channel antagonist is selective for cardiac smooth muscle?
Verapamil (rate limiting)
Which calcium channel antagonist has selectivity for both cardiac and smooth muscle L-type channels?
Diltiazem (rate limiting)
What are the clinical uses of calcium channel antagonists?
Hypertension - amlodipine reduces MAPB
Angina- diltiazem reduces after load + myocardial demand
Arrhythmia- verapamil slows AVN conduction, useful in AF
Which drug must not be used in combination with a calcium channel antagonist?
Beta-blockers
What are the main side effects of calcium channel blockers?
Ankle oedema, hypotension, flushing (dihydropiridines)
Headache, risk of heart block(verapamil)
How does the action of levosimendan cause a positive inotropic effect?
It binds to troponin in cardiac muscle and increases its sensitivity to calcium
What condition can levosimendan be used to treat?
Acute heart failure (given IV)
Which inotropic drugs inhibit PDE?
Amrinone
Milrinone
