What are th four classes of antiarrhythmics?
Class 1: sodium channel blockers
Class2 : Beta blockers
Class 3: K channel blockers
Class 4 : Ca channel blockers
What ions are involved in which stage of the action potential of a working cardiomyocyte?
What would an ECG overlayed on a working cardiomyocyte AP look like?
What do Na channel blockers (class I) do to the AP of a working cardiomyocyte?
What do K blockers (classIII) do to the AP of a working cardiomyocyte?
What ions are involved in the AP of a pacemaker cell?
What do beta blockers (class II) and calcium channel blockers (class 4) to the AP of a pacemaker cardiomyocyte?
What are the pharmocological and invasive treatment options for bradycardia? What kind of bradycardia is each most likely to work for?
Need to speed up the SA node:
- pacemaker to the ventricle
- inhibit PNS (atropine)
- stimulate SNS (epi or dopamine)
**pacing is required for conduction blocks**
**pharmacological works for sinus bradycardia**
What are the different kinds of tachycardia? Which ones are pathologic and need to be treated?
Sinus (can be either)
Atrial (ATach, A flutter, Afib, multifocal atrial tach...ALWAYS pathological)
AV node (always pathological)
Ventricular (always pathologic)
**the last three are usually generated by re-entry circuits, so are treated accordingly**
What are 2 non-pharmacological treatments for tachycardia (of any kind)
- radio-frequency ablation
What do phases 0,1,2,3,4 determine?
0: conduction speed
2/3: refractory period
4: speed of spontaneous depolarization (pacemaker cells)
How would you..
When would sinus tachycardia be pathological?
e.g hyperthyroidism, MI
Generally, class II and IV manipulate ______ and class I and III manipulate______
Class II and IV (b-blockers and Ca channel inhibitors) manipulate pacemaker action potential (lengthen phase 4 and 0 respectively)
Class I and III (Na and K channel blockers) manipulate working cardiomyocyte action potential (conduction speed and refractory period respectively)
How do you treat tachycardias? Hint: divide them into physiological and re-entry
- B-blockers (1st choice) and calcium channel blockers
- beware of clots
- try to break the re-entry circuit (Class 1 and class 3)
- if you can't break the circuit, can try electrical conversion
- if you still can't break the circuit you need to depress the AV node so the heart rate slows down (B-blockers, calcium channel blockers, digoxin)
- vagal maneouvres to "reset" AV node (valsalva, carotid massage)
- pharmcological slowing of AV node (B-blockers, Ca channel blockers, adenosine
- break re-entry circuit in working myocytes (Class I and class III)
***But really you can split them into SVT and VT, because all SVT involves supressing AV node**
Differentiate between cardioversion and defibrillation
Both deliver a shock, but cardioversion is timed to NOT coincide with the T wave (prevent VFib)
What does digoxin do?
Prolongs refractory period in pacemaker cells and increases inotropy
(reduces heart rate and increases stroke volume)
What does atropine do?
Atropine is a mAchR antagonist...it is anticholinergic. It will increase heart rate
Red as a beet
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