Cardiac glycosides and inodilators Flashcards
Maybe know what the general cardiac ECG looks like
P wave: contracting auricles
QRS: sudden depolarization
T wave: potential starts to recover; see hyperpolarization
What species would be likely to see dilated cardiomyopathy?
Doberman
What species would be likely to see endocardiosis/
Cavalier king charles
What are the different classes of CHF?
Class I: only strenuous exercise limited
Class 2: Fatigue, shortness of breath, coughing on exercise
Class 3: Comfortable at rest but exercise is minimal
Class 4: No capacity for exercise, symptoms at rest
What would be used to treat CHF at classes 2-4?
Digoxin
Pimobendan
Ace inhibitors
What is the mechanism of action for cardiac glycosides?
Inhibits Na/K ATPase, which leads to a rise in intracellular Na
Na-Ca exchange system is slowed = increase in sarcoplasmic Ca
Rise in the release of Ca to interact with contractile proteins
Increase in force of contraction and CO; decrease HR
What is the overall effect of cardiac glycosides?
Increase the force of contraction and CO of the heart
decrease the HR
What is a positive inotropic action?
Increased force and velocity of contraction; can be seen in a normal and failing heart
What is a negative chronotropic effect?
slowing of the heart rate
What is the mechanism of a negative chronotropic effect?
Stimulation of the Vagus nerve and improved baroreceptor sensitivity countering sympathetics
What is a negative dromotropic effect?
Slowing of conduction at the AV node
What are some side effects of the cardiac glycosdie Digoxin?
Auricular arrhythmia/tachycardia
AV block
Ventricular arrhythmia
What are some symptoms seen with Digoxin toxicity?
Disturbances in the heart rhythm = extrasystole and coupled beats (pulsus bigemini)
GI disturbances like anorexia, vomiting, diarrhea
How would you treat Digoxin toxicity?
Withdraw Digoxin
Treat ventricular arrhythmias with lidocaine or propranolol
Give IV fluids to maximize renal clearance
What would Pimobendan be classified as?
Inodilator
What is the mechanism of action for Pimobendan?
Ca sensitizer and phosphodiesterase 3 inhibitor
So what does Pimobendan do?
Increases the binding of calcium to Troponin C
PDE 3 inhibitor prevents cAMP breakdown and increases pKA action = increases voltage-gated Ca currents and keeps Ca channels open longer
How does the body respond to Pimobendan or cardiac glycoside treatment?
Increased Cardiac output/decreased heart rate
Decreased venous pressure
Decrease in heart size
Increased water loss and reduced body weight
What are two clinical conditions in vet med that you would use cardiac glycosides?
Endocardiosis
Dilated cardiomyopathy
What is the half-life for Digoxin in dogs, cats, and horses?
Dogs: 23-39 hours
Cats: 25-78 hours; very variable
Horses: 13-23 hours
How is digoxin eliminated from dogs, cats, and horses?
Dogs and cats: mainly renal
What are some other positive ionotropic drugs and what do they do?
Dopamine: D5 receptors on heart increase cAMP
Dobutamine: Beta-1 agonist –> useful IV with acute, reversible heart failure
Amrinone: PDE 3 inhibitor; good for IV to increase cAMP which increases Ca influx
