Week 11- Therapeutics for Cardiovascular Disease Flashcards
What two drugs affect myocardial cells directly?
- Antidysrhythmic drugs
- Cardiac glycosides and other inotropic drugs
What three drug types affect the cardiac cycle indirectly?
- Drugs acting on the RAAS
- Diuretics
- Calcium Channel Blockers
What do class I antidysrhythmic drugs do?
- Blocks Na+ Channels
- Reduces the max rate of depolaristaion during phase 0
What do class II antidysrhythmic drugs do?
B-adrenoceptor antagonists, slow SA node and increased refractory period of the AV node
What do class III antidysrhythmic drugs do?
- Complex
- Block K+ channels and prolong cardiac action potentials
What do class IV antidysrhythmic drugs do?
- Block voltage sensitive Ca2+ channels
- slow conduction in the SA and AV nodes
What is the function of lidocaine?
- rapid onset of action
- relatively safe
- first choice treatment of ventricular tachyarrhythmia
What is the lidocaine bolus duration of action?
- short duration of action (10-15 minutes)
- continuous rate infusion if required
What should you not use lidocaine with?
Do not use lidocaine and adrenaline solutions for injection
What is guinidine used for?
Competition horses with atrial fibrillation
What does stimulation of Beta Adrenoceptors in the heart by endogenous catecholamines do?
- Increased heart rate in the SA node
- Increased atrial cardiac muscle contractility
- Increased contractility and automaticity of ventricular cardiac muscle
- Increased conduction and automacity of AV valve
What do beta- adrenoceptor antagonists do?
- Competitive antagonists
- reduce cardiac O2 filling
- slow HR and improve filling
What are atenolol and metaprolol?
Beta 1- adrenoceptor selective antagonists
What is sotalol?
Class III- chronic treatments of ventricular and supraventrciular tachyarrythmias- avoid in patients with CHF
What is amiodarone?
Primarily Class III action, slow and variable GI absorption, slow onset of action, variable efficacy, high frequency on non-cardiac events
* Monitor plasma K+ events
What is sotalol used for?
Chronic treatment of ventricular and supraventricular tachyarrhythmias
What is amiodarone used for?
Primary class III action, slow and variable GI absorption, slow onset of action, variable fficacy, high frequency of cardiac events,
What is diltazem?
Primarily used for supraventricular tacharrhthmias, atrial tachycardia and flutter. Also used for hypertrophic cardiomyopathy
What is verapamil?
Coexistence of atrial fibrillation, with re-entrant may be contraindication for use of these for use of these agents- may exacerbate
What is digoxin?
decreases heart rate by reducing the frequency of SA firing and inhibiting AV nodal conduction. Used to treat atrial fibrillation
How do you reverse bradyarrhythmia?
Reverses excess vagal activity with atropine or glycopyyrolate
- pacemaker
How can you fix a ventricular dysrhythmia?
- Lidocaine
- Procainamide
How would you fix a supraventrciular dysrhythmia?
- Digoxin
- Calcium Channel Blockers
How would you fix a bradyarrythmia?
- Atropine
- Pacing
What is a cardiac glycoside?
- Derived from foxgloves
- Increases the force of contraction
- slows the heart and incraeses conduction rate through AV node by increasing vagal outflow
- Combination of slower HR and increased contraction force increases CO- used to treat heart failure as well as superventricular arrhythmias
What is the main caution of cardiac glycosides?
- narrow therapeutic window
- may cause excessively low heart rates
- cats are more sensitive to toxic effects than dogs
What is an inodilator?
- have both a positive inotropic effect and vasodilatory action
What is pimobendane?
Phosphodiesterase inhibitor
increases intracellular calcium and myocardial oxygenation
* used for mitral valve disease
What is dobutamine?
- Direct acting synthetic catecholamine with direct Beta adrenergic agonist effects- positively inotropic
- used to address hypotension
- potent and short acting
- produces less tachycardia than other beta agonists
- used in emergencies for management of acute heart failure
What does RAAS contribute to?
The pathogenesis of heart failure
What inhibitors are used to manage hypertension?
- benazepril
- enalapril
What are the most powerful diuretics?
- Loop diuretics
- inhibit the H+/ K+ co-transporter
What is furosemide commonly used for?
Treat almost all cases of congestive heart failure
What is torasemide?
- Loop diuretic
- longer duration of acting
- (good for angry cats)
What is spironolactone?
- act as specific antagonists of aldosterone
- exert their effects by binding competitively to the mineralcorticoid receptor located in the kidneys, heart and blood vessels
What is a thiazide diuretic?
- less powerful than loop diuretics
- used as second or third line diuretics in end stage heart failure
- disproportionate chloride loss that can result in acid-base disturbances and hypokalaemia
What is the function of amlodipine?
- Blocks calcium channels in vascular smooth muscle
- gradual onset and slow waning effect because of its slow binding and dissociation from the channel
- little reflex tachycardia occurs making it a safe drug to use for hypertension
