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Cardiovascular 2 > Drugs for Arrhythmias - Konorev > Flashcards

Drugs for Arrhythmias - Konorev Flashcards

1
Q

Sodium channel gates in a voltage-gated Na channel

A

M gates = open during activation (depolarization)

H gates = close during inactivation (repolarization)

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2
Q

The resting membrane potential is largely regulated by ____ channels

A

Potassium

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3
Q

In the resting (polarized) state, ____ potassium channels are open.

Is there a current through them?

A

Inwardly-rectifying

NO current - electric gradient in equilibrium with concentration gradient

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4
Q

During phase 3 of the action potential (repolarization), ____ potassium channels open up.

Function?

A

Voltage-gated

Limit the frequency and duration of action potentials and refractory period

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5
Q

Which cardiac tissues use a FAST action potential?

A

Myocytes and purkinje fibers

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6
Q

Which cardiac tissues use a SLOW action potential?

A

SA and AV nodes

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7
Q

Flow of which ion (channel) is responsible for phase 2 (plateau) of the fast action potential?

A

Slow voltage-dependent calcium (inward flow)

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8
Q

Flow of which ion is responsible for phase 0 (rise) of the fast action potential?

A

Sodium

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9
Q

Phase 0 channels

A

Voltage-gated fast Na+

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10
Q

Phase 1 ion flow (brief repol.)

A

Voltage-gated K+ OPEN

Fast Na+ CLOSE

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11
Q

Phase 3 ion flow (start of rapid repol.)

A

Ca+ channels close

K+ begins to exit more rapidly

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12
Q

Restoration of resting membrane potential (refractory period)

A

Na/K ATPase and Na/Ca exchanger

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13
Q

Phase 4 channels of pacemaker potential

A

Funny Na+ current (open during hyperpolarization)

Slow Ca+ T-type channels (just before depolarization)

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14
Q

Phase 0 channels of pacemaker potential

A

L-type (long-acting) Ca+ channels

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15
Q

Phase 3 of pacemaker potential

A

K+ efflux, closing of Ca+ channels

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16
Q

3 factors that influence the rate of the pacemaker

A
  • Rate of spontaneous depolarization in phase 4
  • Threshold potential (more negative = easier to depol.)
  • Resting potential (less negative = easier to depol.)
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17
Q

Function of sympathetics on pacemaker rate (pathway of events) - KNOW THIS

A

Beta-1 –> increased AC –> increased cAMP –> increased funny channel flow rate and decreased calcium channel threshold –> increased pacemaker speed

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18
Q

Function of parasympathetics on pacemaker rate (pathway of events) - KNOW THIS

A

M2 –> decreased AC and increased K+ opening –> slower funny currents, higher threshold (via less cAMP/PKA for Ca++ channels), and lower resting potential

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19
Q

What is an early afterdepolarization? Cause?

A

Another rapid depolarization during phase 2 or 3 of the previous action potential – caused by impaired K+ channels and prolonged repolarization period

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20
Q

Torsades de pointes - will see ______

A

Long QT syndrome (prolonged repolarization)

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21
Q

Do not give a Torsades de Pointes (long QT) inducing drug IF ______

Which ones are long-QT inducing?

A

QT is > 450 ms

  • Class 1A or Class C antiarrhythmics
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22
Q

What is a delayed afterdepolarization? Cause?

A

Another partial depolarization during phase 4 (hyperpol.) DUE TO INCREASED CYTOSOLIC Ca++

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23
Q

3 causes of increased cytosolic Ca++

A

Digoxin toxicity, catecholamine excess, myocardial ischemia/reperfusion

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24
Q

A patient is on Digoxin, but starts experiencing heart beat issues. Explain.

A

Digoxin –> spontaneous Ca++ release from SR after an action potential –> 3Na/Ca exchanger –> net depolarization of membrane –> premature ventricular beats (bigeminy)

25
Q

Class 1 antiarrhythmic drugs - function

A

Sodium channel blockers

26
Q

Class 1A drugs - names

A
  • Quinidine
  • Procainamide
  • Disopyramide
27
Q

Class 1B drugs - names

A
  • Lidocaine

- Mexiletine

28
Q

Class 1C drugs - names

A
  • Flecainide

- Propafenone

29
Q

Class 2 antiarrhythmic drugs - function

Names?

A

Beta blockers

  • Esmolol
  • Propranolol
30
Q

Class 3 antiarrhythmic drugs - function

Names?

A

K+ channels blockers

  • Amiodarone
  • Dronedarone
  • Sotalol
  • Dofetilide
31
Q

Class 4 antiarrhythmic drugs - function

Names?

A

Cardioactive CCBs

  • Verapamil
  • Diltiazem
32
Q

Miscellaneous antiarrhythmic agents

A
  • Adenosine

- Magnesium

33
Q

State-dependent blocks

A

Drugs block ion channel during certain stage in the cycle (active, inactive, resting)

34
Q

Functions of class 1A antiarrhythmics

A
  • Slow impulse conduction and reduce rate of pacemaker cells
  • Binds ACTIVE sodium channels
  • Blocks potassium channels
  • Prolong action potential, QRS duration, and QT interval
35
Q

Procainamide

  • Uses? (6)
  • Function?
  • Adverse effects?
A
  • WPW, PAC, PVC, A fib, V tach, A flutter
  • Depress SA and AV nodes (sodium channel blocker)
  • QT prolong (TdP), lupus-like syndrome, hypersensitivity reactions
36
Q

Quinidine

  • Functions? (3)
  • Uses?
  • Adverse effects?
A
  • Slows velocity of conduction system, decreased automaticity of ectopic foci, and prolongs refractory period in heart
  • MAT, PAC, PVC, A. fib, V. tach.
  • QT prolongation (TdP), many neural symptoms, thrombocytopenic purpura
37
Q

Disopyramide

  • Uses? (3)
  • Adverse effects?
A
  • A fib, V tach, PAC

- QT prolongation (TdP), excess sympathetics effects

38
Q

Functions of class 1b antiarrhythmics

Benefit of these?

A
  • Binds INACTIVE sodium channels, mostly in depolarized (damaged) tissue
  • Shorten action potential
  • Do NOT block K+ channels –> no prolonging QT or AP
39
Q

Lidocaine

  • Uses? (4)
  • Functions?
  • Adverse effects?
A
  • WPW, V tach, PVC, V fib
  • Silences ectopic foci, increases conduction in His-Purkinje system
  • Hypotension via inhibited contractility, neurologic deficits
40
Q

Mexiletine

  • Uses? (2)
  • Functions?
  • Adverse effects?
A
  • Life-threatening ventricular arrhythmias (VT), PVC
  • Silences ectopic foci and slows AV node, prolongs refractory period for junctional and ventricular pathways
  • Hepatotoxicity, seizures
41
Q

Functions of class 1c antiarrhythmics

A

Binds ACTIVE sodium channels and some potassium channels

42
Q

ECG effect of class 1c drugs

A
  • LONG QRS
43
Q

Flecainide

- Clinical use?

A
  • Chronic therapy for long-term V. tach, supraventricular arrhythmias
44
Q

Propafenone - adverse effects

A
  • Metallic taste
  • Constipation
  • Exacerbation of ventricular arrhythmias or HF
45
Q

Propafenone - MoA (2)

A
  • Increase refractory period and decrease conduction velocity through heart
  • Weak BETA-BLOCKING ability
46
Q

Functions of beta blockers (class 2 drugs) (2)

A
  • Slow action potential (slow down SA and AV nodes)

- Prevent delayed afterdepolarizations (decrease Ca++ overload)

47
Q

Uses of Propranolol and Esmolol with arrhythmias

A
  • Stress-associated sinus tach.
  • AV nodal re-entrant tachycardia
  • A fib, A flutter
  • WPW syndrome
48
Q

Function of class 3 drugs

A
  • Block potassium channels – prolong AP and QT
49
Q

Amiodarone

  • Use?
  • Adverse effects?
A
  • Ventricular arrhythmias

- AV block, bradycardia, pulmonary fibrosis, hepatitis, blue-gray skin discoloration, optic neuritis, thyroid problems

50
Q

Dronedarone

  • Functions?
  • Use?
  • Adverse effects?
  • CONTRAINDICATION?
A
  • Blocks K+ channels, Na+ current, L-type Ca++ current
  • A. fib/flutter
  • Worsening heart failure, GI stuff
  • INCREASED MORTALITY w/ decompensated HF
51
Q

Sotalol

  • Functions?
  • Uses?
  • Adverse effects?
A
  • Beta-blocker AND AP prolonger
  • Vent. arrhythmias, maintianing sinus rhythm w/ A. fib.
  • Cardiac depression, TdP INDUCTION
52
Q

Dofetilide

  • Function?
  • CAUTION?
  • Use?
  • Adverse effect?
A
  • Blocks rapid part of rectifier K+ current (lower HRs)
  • NARROW THERAPEUTIC WINDOW
  • Converts AF to sinus rhythm
  • QT prolongation, risk of ventricular arrhytmias
53
Q

Function of class 4 drugs

A
  • Blocks all L-type calcium channels
  • Decreased slope of phase 0 depolarization
  • Prolong SA and AV node APs and refractory periods
54
Q

Uses of Cardiogenic CCBs

A
  • Prevent paroxysmal SVT

- Control rate in AF and A. flutter

55
Q

Adverse effects of cardiogenic CCBs

A
  • AV block, weaken contractility, hypotension, CONSTIPATION (VERAPAMIL)
56
Q

Function of Adenosine

A
  • Activate K+ current, inhibit Ca++ and funny currents –> hyperpolarization of SA and AV nodes
57
Q

Use of Adenosine

Adverse effects?

A
  • Convert paroxysmal SVT to sinus rhythm

- SoB, bronchoconstriction, chest burning

58
Q

Uses of magnesium

A
  • Digitalis arrhythmia

- TdP

Cardiovascular 2 (20 decks)

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