Inotropes Flashcards
What is digoxin?
Cardiac glycoside that competes with K+ and blocks Na+/K+ pump leaving more Na+ in the cell to pump out in exchange for Ca2+ on Na/Ca exchanger
Does digoxin inc HR?
No, inc inotropy w/o inc in HR
List some pharmacological properties of digoxin
- long half-life
- oral
- Quick onset
How is digoxin eliminated?
Renal
What does digoxin do to the CO?
Inc
What does digoxin do to the LVEF?
inc
What does digoxin do to the LVEDP?
Decrease (ie preload)
What does digoxin do to exercise tolerance?
Inc
What does digoxin do to natriuresis?
Inc (Excretion of Na and H2O from kidney)
What does digoxin do to the neurohormonal activation?
Dec
-Hrt works better, body doesn’t need as many hormones
What does digoxin do to the levels of plasma norpei
Dec
What does digoxin do to the peripheral NS activation?
dec
What does digoxin do to the RAAS activity?
Dec
What does digoxin do to vagal tone?
Increases, helps with HR control and normalizes arterial baroreceptors (were desensitized before administration of drug–>drug dec preload)
What is digoxin’s effects on the Atrial and AV node?
Decreases “automaticity” via increase in vagal tone and decrease in sympathetic activity (i.e. dec how quickly cells can cycle and fire again)
Increases refractory period of AV node in toxicity (high levels) and can lead to bradycardia and heart block
–>i.e. increase in PR invterval
What are digoxin’s effects on the ventricles?
Increases isotropy at therapeutic doses
At toxic doses, can inc sympathetic tone and directly inc automaticity leading to increased risk of ventricular tachycardia and fibrillation
What are inotropes?
Agents that increase cardiac contractility for our purposes by increasing intracellular Ca2+ and cAMP
Why are inotropes helpful in HF?
In HF, there is a reduction in the rate and extent of Ca2+ delivery to myofilaments, resulting in reduced contractility
What do inotropes do to the frank-starling curve?
Shifts them upward and left (greater end diastolic volume/preload and greater SV)
What are the clinical uses of Digoxin?
- A fib with rapid ventricular response (increase AV nodal refractory period, more effective at rest than with exercise)
- CHF symptoms despite medical therapy (don’t give an asymptomatic person the drug because you’ll only get the negative effects without the pos dec in symptoms)
- Can be combined with other drugs
What are the negative long term effects of digoxin?
Increased MIs
More serious arrhythmias–vent tacky or fib
What are the positive long term effects of digoxin?
Fewer hx admissions for heart failure
What factors predispose people to digoxin toxicity?
Hypokalemia, hypomg, hypothyroidism, hypoxia
Drug interactions are common!