Treatment of dysrhythmias

Question 1

Treating dysrhythmias with drugs can often make the problem worse. How else could we treat?

Answer 1

Eliminate the cause:

1. ) lower dose of digitalis
2. ) Relieve ischaemia
3. ) Withdraw drug causing long QT
4. ) Withdraw drug causing sympathetic overstimulation (dobutamine)
5. ) Implant a pacemaker

Question 2

Another way to target dysrhythmia is to prevent transmission from bad cell. How do we do this?

Answer 2

By reducing the overall activity of the heart

Question 3

What are the 4 classes of anti-dysrhythmic drugs?

Answer 3

1. ) block voltage gated sodium channels
2. ) Beta adrenoceptor antagonist (bblocker)
3. ) Increase AP length
4. ) Voltage gated ca2+ channel blocker

Question 4

How do each of these classes work?

Answer 4

1. ) Na+ is essential in activating an AP = blocking makes it harder to stimulate without a large stimuli
2. ) Arrhythmia is often associated with an overactive SNS =more noradrenaline is released which acts on b-receptors to increase HR. B-blockers dampen down these effects and slow HR
3. ) Increase AP lenght by blocking voltage gated k+ channel = takes longer for cell to repolarise = refractory period is longer = slows HR down but if increase length too much will get a ca2+ overload and this will make problem worse
4. ) Good in DAD. Reduces amount of intracellular ca2+ = reduced the activity of sodium calcium exchanger.