AP and Antiarrhythmics Flashcards
What is the process of electrical conduction in the heart?
- SA node fires
- Excitation spreads through atrial myocardium
- AV node fires
- Excitation spreads down AV bundle
- Purkinje fibers distribute excitation through ventricular myocardium
What do pacemaker cells have?
Automaticity
What are the channels in the sodium channels?
Voltage gated, Nav1.5
What are the channels in the calcium channels?
N type Cav2.2, t type Cav3.x
What are the channels in the potassium channels?
Kir, Kv
What are the channels in the HCN channels?
HCN1, HCN4
What is the channel to avoid when developing new drugs?
hERG
What are pacemaker cells?
- Specialized, non-contractile cells
- Physiologically depolarized
- High automaticity
- Ca dependent spikes
What are ventricular myocytes?
- Contractile cells
- Hyperpolarized
- Low automaticity
- Na dependent spikes
What drugs are in the class 2 beta adrenergic antagonists?
Esmolol, Acebutolol, Propranolol
What are the clinical uses of class 2 beta adrenergic antagonists?
- Arrhythmias involving catecholamines
- Atrial arrhythmias (protect ventricular rate)
- Post MI prevention of ventricular arrhythmias
- Prophylaxis in long QT syndrome
Specifics of esmolol:
- Cardioselective (b1 AR)
- 9 min half life due to plasma esterase hydrolysis
- Given IV
Specifics of acebutolol:
- Cardioselective
- Weak partial agonist at b1 AR (sympathomimetic)
- Weak Na channel blockade
Specifics of propranolol:
- Non selective
- Weak Na channel blockade
What drugs are in the class 4 Ca channel blockers?
Verapamil, Diltiazem
Specifics of verapamil:
- Frequency dependent block of Ca1.2 channels
- Selective block for channels opening more frequently
- Accumulation of blockade in rapidly depolarizing tissue (ie tachycardia)
Specifics of diltiazem:
- Block re-entrant arrhythmias involving AV node
- Protect ventricular rate in atrial flutter and afib
What is the drugs in class 1A Na channel blockers?
Quinidine, Procainamide, Disopyramide
What is the drugs in class 1B Na channel blockers?
Lidocaine, mexiletine
What is the drugs in class 1C Na channel blockers?
Flecainide, Propafenone
What are the effects of class 1A drugs on action potential?
- Mixed block: Na and K channels
- Blocks open state
- Moderate, incomplete dissociation
- Widen QRS
- Prolonged QT
What are the effects of class 1B drugs on action potential?
- Na channel block
- Blocks open and inactivated state
- Rapid, complete dissociation
- Slight narrowing of action potential
- No clinically sig effect on ECG
What are the effects of class 1C drugs on action potential?
- Strong Na channel block
- Blocks open state
- Very slow, incomplete dissocation
- Widen QRS
What is the MOA of class 3 K channel blockers?
- Block Ikr, prolong action potential duration and QT interval
- Increases effective refractory period
- IN re-entrant circuit, increased ERP above conduction time around circuit will terminate re-entry
