Anti-arrythmics

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 1

What are the main indications for Digoxin?

Answer 1

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 2

What are side-effects and contraindications of Digoxin?

Answer 2

Can worsen conduction abnormalities so contraindicated in

• 2nd and 3rd degree Heart block
• Ventricular arrythmias

Question 3

What are signs of Digoxin toxicity/ overdose?

Answer 3

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 4

Explain the conduction of the modified valsalva maneuver

Answer 4

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

Question 5

What is amiodarone?

What is the MOA?

Answer 5

Complex effect on many channels but overall

1. reduces spontaneous depolarasation
2. slow conduction velocity
3. and increased resistance to depolarisation, including the AV node

–> reduction of Ventricular rate in AF and atrial flutter

Question 6

What are the main indications for the use of Amiodarone?

Answer 6

Many tachyarrythmias

1. AF, Atrial flutter and SVT
2. VT and VF

usually only if other treatements ineffective or contraindicated

Question 7

What are the side-effects and contraindications to use of Amiodarone?

Answer 7

Contrainicated in

• severe hypotension
• heart block
• active thyroid disease (due to iodine core)

Side effects

• very few acutely
• but long term inlcude pneumonitis, bradicardia AV block, hepatitis, photosentiivity and thyroid diseae (+ has extremely long (months) half-life + needs loading dose when starting)

Question 8

In what point of the ALS algorythm should amiodarone be given?
Why?

Answer 8

1. If VF or pulseless VT after 3rd shock
2. 300mg IV followed by flush (10ml saline or 5% glucose)

Question 9

What is Adenosine? What is the MOA?

Answer 9

It is an anti-arrythmis drug (adenosine receptor agonist) causing

Reducing HR and increases AV node refractory period:

• reducing the frequency of sponaneous depolarisation
• increasing the resistance to depolarisation

Question 10

What is the indication for Adenosine?

Answer 10

Emergency drug and first line (after valsalva) in SVT without life-threatening features (otherwise electrical cardioversion)

Question 11

What are the contraindications to Adenosine?

Answer 11

hypotension
coronary ischaemia
decompensated Heart failure
Asthma (due to bronchoconstriction)

Caution on people with

• COPD
• Heart transplans

Question 12

What is the dose of adenosine in medical treatment of SVT?

Answer 12

6mg IV once, in ineffective followed by 12mg and then 18mg as rapid injection

but cuases very unpleasent experience (and might cause brief, transient asystole and severe bradicardia during administration and seconds after) + must be done with cardiac monitoring