Anti-arrhythmics

Question 1

What is the Mechanism of Action of Digoxin?

Answer 1

Depending on the indication

• negatively chronotropic (reduces HR) and
• Positively inotropic

AF+ Atrial flutter
* increases parasympathetic tone indirectly –> reduction of conduction at AV node –> reduction of ventricular rate

Heart Failure
* Inhibition of NA+/K+ ATP-ase–> Na+ accumulation in the cells
* Higher NA+ –> higher intracellular Ca+ (as Ca+ expulsion requires low intracelluar NA+)
* Increased contractile force

Question 2

What are the main indications for Digoxin?

Answer 2

1. AF and ATrial Flutter (usually not until Betablocker or CCB used, used less because is uneffective with high sympathetic activity (exercise + stress))
2. Severe heart failure

Question 3

What are side-effects and contraindications of Digoxin?

Answer 3

Can worsen conduction abnormalities so contraindicated in
* 2nd and 3rd degree Heart block
* Ventricular arrythmias

Question 4

What are signs of Digoxin toxicity/ overdose?

Answer 4

Can be unspecific but halmarks include

• Abdominal pain
• nausea, vomiting
• and yellow-tinged, blurry vision (chronic poisoning)
• Unspecific Arrythmias (can cause any arrythmia, particularly bradyarrythmias

ST-segment depressions can occur at therapeutic dose and don’t have to be signs of toxicity

Question 5

Explain the conduction of the modified valsalva maneuver

Answer 5

1. Patient blowing against resistance (e.g. into a 10ml syringe) for 15s
2. Afterwards the patient is laid supine and the legs are passively elevated to 45° for 15 seconds.
3. Return to the semirecumbent position for 45 seconds before reassessing rhythm