Lecture 19: CV Pharmacology Flashcards
(49 cards)
How does a SA node action potential look like?
- Sodium influx via funny channels
- Calcium influx
- Potassium efflux
What are the 5 phases of a cardiac myocyte action potential?
What is the effect of hypercalcemia on the cardiac action potential?
Extends the plateau phase
What are the 2 general mechanisms behind arrhythmias?
- Abnormal pacemaker activity
- Abnormal impulse propagation
What do antiarrhythmic drugs tend to focus on?
Ectopic pacemakers, reducing their automaticity.
It does not affect the SA node itself as much.
What do antiarrhythmic drugs do to depolarized tissue primarily?
- Reduce conduction and excitability
- Increase refractory period
Effect is more pronounced in depolarized tissue rather than polarized.
What are the 4 classes of antiarrhythmic drugs?
- Class I: fast sodium channel blockers
- Class II: BBs
- Class III: Potassium channel blockers
- Class IV: CCBs
What are the 3 subclasses of class I antiarrhythmics based on and what are the 3 subclasses?
Defined by their effects on purkinje fiber AP
- Class 1a: slow the rate of rise of the AP and prolong its duration (moderate depression of the phase 0 upstroke) (Quinidine, procainamide, disopyramide)
- Class 1b: Shorten AP (minimal depression of the phase 0 upstroke) (lidocaine, mexiletine)
- Class 1c: Dissociates from channel with slow kinetics (no change in AP duration) (flecainide, propafenone)
What is the main purpose of quinidine and what is it often used with?
- Class 1a drug that works as an anticholinergic on SA and AV nodes.
- Often combined with BBs, non-DHP CCBs, or digoxin to prevent increased ventricular rate.
Proarrhythmic that can cause torsades
What does procainamide do?
- Similar to quinidine but lacks anticholinergic activity.
- Prolongs QT interval = torsades risk
- MC ADE: Lupus
- Main use: WPW
Class 1a
Treats Wolff, can cause wolf
What is the profile of disopyramide?
- Class 1a
- Potent anticholinergic and negative inotrope
- QT prolongation
- CI in pts with HFrEF
What is lidocaine selective for in the heart?
Ischemic tissue, primarily active fast sodium channels below the AV node
Class 1b
Class 1a antiarrhythmic mnemonic
Double Quarter Pounder
- Disopyramide
- Quinidine
- Procainamide
When is lidocaine used?
Ventricular dysrhythmias, especially those associated with MI.
What kind of patients should we be cautious of injecting lidocaine into?
Hepatic impairment
What is the difference between lidocaine and mexiletine?
Mexiletine is oral
class 1b
What is mexiletine often used with combination with?
Class 1a and III for refractory ventricular dysrhythmias
What is the main SE of mexiletine?
GI use (limits the use of them)
What is the profile of flecainide?
- Slows conduction velocity in the purkinje and AV node
- MC use: afib/aflutter
- May cause rapid VT in someone with structural abnormalities
Class 1c
Class 1b antiarrhythmic mnemonic
Lettuce Tomato Mayo
- Lidocaine
- phenyToin
- Mexilitine
Liddy’s Mexican Pub
T is actually for tocainide, but we didn’t learn about it
What is the profile of propafenone?
- Slows conduction velocity in the purkinje fibers and AV node + mild non-selective BB effect
- lengthens PR and QRS => bradycardia or heart block
- MC use: Afib/Aflutter
- Avoid in structural heart disease
- Additional SE of metallic taste
Class 1c
Similar to flecainide
What patients should never get class 1c antiarrhythmics?
Structural Heart Disease
What are BBs mainly used for?
- Decrease automaticity, prolong AV conduction, prolong refractory period
- Suppressing ventricular dysrhythmias and SVTs
Class 1c antiarrhythmic mnemonic
Fries Please
- Flecainide
- Propafenone
