Lecture 10: Inotropic Agents and Pharmacology of Heart Failure Flashcards
What drug class is Digoxin?
Cardiac Glycosides
What are the 3 primary mechanisms by which inotropes (increase heart muscle contractions) affect cardiac muscle?
- Increasing intracellular Ca2+ (Cardiac Glycosides = Digoxin)
- Increasing intracellular cAMP (Symphatomimetics = Dobutamine)
- Decreasing breakdown of cAMP (PDE III inhibitors)
Explain calcium-induced calcium release (6)
- Na influx causes depolarization
- After depolarization, calcium flows in
- Calcium binds to RyR receptors and causes conformational change releasing calcium from SR
- Calcium from SR causes contraction
- Na/Ca exchanger removes calcium from the cytosol
- Na/K pump releases calcium to maintain gradient
Review slide 6
Review slide 6
Pharmacodynamics of Digoxin
How does digoxin affect heart failure (3)?
- Decreases sympathetic tone
- Decreases plasma norepinephrine
- Decreases RAAS activity
What are the pharmacodynamics of Digoxin (2)?
- Positive inotropic effect
- Increases vagal tone (increases sodium in the cell = depolarization = increases vagal tone)
- Also inhibits Na/K pump in neurons
Digoxin Clinical Use
How does Digoxin treat heart failure?
- inotropic agent
- helps the heart contract and pump
Digoxin Clinical Use
How does Digoxin treat atrial fibrillation?
- Controls ventricular response rate
- Prevents ventricular tachy or fib
Digoxin Clinical Use
How does Digoxin treat atrial fibrillation in heart failure?
rate control
What are the clinical effects of Digoxin in heart failure (4)?
- Improve symptoms
- Modest reduction in hospitalization
- Lower plasma concentrations in the therapeutic range improve survival
- Higher plasma concentrations in the therapeutic range may increase mortality
Therapeutic range is very low
What are the consequences of cell depolarization by Digoxin (5)?
- Increases vagal activity = increases Na deploarization of vagal neurons
- Decreases S-A Node Rate
- Increases Automaticity
- Increases ectopic beats
Slide 10
Na can _____ so much that it will _____ the antiporter. 3 Na out and 1 Ca in
- increase
- reverse
Review slide 12
Review slide 12
What are the electrical signs of toxicity (3)?
- Loss of plateau
- RMP becomes more positive
- Delayed after depolarization
Review slide 13
Review slide 13
What are the cardiac adverse reactions of Digoxin (5)?
- Asystole = increases vagal tone
- Atrial tachycardia
- AV block
- Premature ventricular contractions (PVCs)
- Syncope
What are the non-cardiac (increases parasympathetic) adverse reactions of Digoxin?
- Diarrhea
- Nausea/Vomiting
What is the therapeutic index for Digoxin?
2
Want 10
What are Digoxin contraindications that affect cardiac muscle (2)?
- Ventricular fibrillation (absolute contraindication)
- Ventricular arrhythmias/tachycardia
Increases cardiac muscle b/c increases excitability of heart
What are Digoxin contraindications that affect the vagus nerve (4)?
- Wolf-Parkinson-White Syndrome
- AV block
- Bradycardia
- Sick sinus syndrome
Increases vagus nerve b/c increases AV node
Digoxin toxicity
What is the treatment for 1st degree heart block and ectopic beats?
reduce dose
Digoxin toxicity
What is the treatment for advanced heart block?
Atropine
block parasympathetic
Digoxin toxicity
What is the treatment for increased automaticity?
KCL
K and digoxin competing for same binding site
Digoxin toxicity
What is the treatment for toxic serum concentration ; acute toxicity?
Fab antibodies
What occurs when heart failure progresses (3)?
- Heart damage = blood is not pumping
- RAAS/Sympathetic increases
- Heart is trying to compensate = causes more damage
Slide 18
What is the severity of Stage A?
- **High risk **for developing HF
- **No structural heart disease **