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Dysrhythmias Flashcards

1
Q

What is a dysrhythmia?

A

Any disturbance of heart rate or rhythm

Synonym: Arrhythmia (technically, no rhythm).

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2
Q

How common are dysrhythmias in the UK?

A

Over 2 million people have a dysrhythmia

Risk increases with age.

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3
Q

What is the most common type of dysrhythmia?

A

Atrial fibrillation

Accounts for 1.6% of NHS budget.

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4
Q

What are the classifications of dysrhythmias based on site of origin?

A
  • Ventricular
  • Supraventricular
  • Atrial
  • Nodal
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5
Q

What are the classifications of dysrhythmias based on effect on rate or rhythm?

A
  • Bradycardia
  • Tachycardia
  • Fibrillation
  • Flutter
  • Block
  • Paroxysmal
  • Sinus
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6
Q

What are some examples of dysrhythmias?

A
  • Atrial fibrillation
  • Paroxysmal supraventricular tachycardia
  • Sinus bradycardia
  • AV node block
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7
Q

What are some causes of dysrhythmias?

A
  • Structural damage
  • Ischaemia
  • Past heart attack
  • Genetic disorder
  • Metabolic disorder
  • Hyperthyroidism
  • Electrolyte imbalances
  • Increased ANS activity
  • Drugs (e.g., caffeine)
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8
Q

What are the five main mechanisms of dysrhythmias?

A
  • Ectopic pacemaker
  • After-depolarization
  • Heart block
  • Re-entry circuits
  • Accessory pathways
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9
Q

What is an ectopic pacemaker?

A

Abnormal site generating electrical impulses distinct from the SA node

All cardiac muscle has automaticity.

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10
Q

What are the two classes of after-depolarization?

A
  • Early – prolonged calcium influx in phase 2/reduced potassium efflux in phase 3
  • Delayed – calcium build-up in the cytoplasm
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11
Q

What is heart block?

A

Damage to the conduction system

Three degrees: first-degree, second-degree, third-degree.

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12
Q

What characterizes first-degree heart block?

A

Delayed conduction by AV node

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13
Q

What characterizes second-degree heart block?

A

Not all P waves transmitted to ventricles

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14
Q

What characterizes third-degree heart block?

A

No AV node conduction; ventricular tissue takes over as a slow pacemaker

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15
Q

What is a re-entry circuit?

A

Occurs when impulse loops through conduction system or muscle

Can be local (e.g., AV node) or global.

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16
Q

What is the most common type of accessory pathway dysrhythmia?

A

Wolff-Parkinson-White syndrome

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17
Q

What is atrial fibrillation?

A

Most common dysrhythmia; atrial rate up to 600 bpm

Increases risk of thromboembolism.

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18
Q

What is ventricular fibrillation?

A

Ventricles cease beating in a coordinated way, leading to no cardiac output

Rapidly fatal; may require DC shock for restoration.

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19
Q

What is the Vaughan Williams system used for?

A

Classification of drugs used to treat dysrhythmias

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20
Q

What are the four classes in the Vaughan Williams system?

A
  • Class I: Sodium channels
  • Class II: Beta 1 adrenoceptor
  • Class III: Potassium channels
  • Class IV: Calcium channels
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21
Q

What is the mechanism of action of amiodarone?

A
  • Blocks potassium channels
  • Inhibits beta adrenoceptors
  • Blocks calcium channels
  • Inhibits sodium channels
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22
Q

What are the side effects of amiodarone?

A
  • Lung fibrosis
  • Eye deposits
  • Liver toxicity
  • Skin discoloration
  • Thyroid function interference
  • Can worsen bradycardias or AV node block
23
Q

What is the mechanism of action of verapamil?

A

Negative chronotropic effect on SA node and slows AV node conduction

24
Q

What are common side effects of verapamil?

A
  • Bradycardia
  • Worsens heart block
  • Vasodilation effects (flushing, hypotension)
  • Constipation
25
What is the role of atropine in dysrhythmias?
Used to treat bradycardias, especially in emergency situations ## Footnote Mechanism involves down-regulation of the SA node by the vagus nerve.
26
What system is critiqued for its weaknesses in drug classification?
Vaughan Williams system ## Footnote The Vaughan Williams classification system categorizes antiarrhythmic drugs but has limitations that necessitate expansion.
27
What is atropine primarily used to treat?
Bradycardias, especially in emergency situations ## Footnote Atropine is often administered during surgery to manage heart rate.
28
What type of receptor mediates the effect of the vagus nerve on the SA node?
M2 mAChR ## Footnote M2 muscarinic acetylcholine receptors are involved in heart rate regulation.
29
What are common side effects of atropine?
* Constipation * Blurred vision * Dry mouth * Higher doses: confusion, delirium ## Footnote Atropine acts as a non-selective mAChR antagonist.
30
What is the role of adenosine in the cardiovascular system?
Signal in its own right ## Footnote Adenosine interacts with specific receptors (A1, A2A, A2B, A3) to affect heart function.
31
Which receptor is important in the AV node and is coupled to Gi?
A1 receptor ## Footnote The A1 receptor plays a crucial role in regulating heart rhythm at the AV node.
32
What is the duration of action for adenosine when given as an IV bolus?
20-30 seconds ## Footnote Adenosine has a very short plasma half-life, making it effective for rapid interventions.
33
What are some uses of adenosine?
* Terminating dysrhythmias * PSVT * AV node dependent tachycardias in WPW ## Footnote Adenosine has largely replaced verapamil for these uses.
34
What side effects can adenosine cause?
* Bradycardia * Worsening heart block * Facial flushing * Chest pain * Bronchospasm ## Footnote Adenosine interacts with other stimulants like caffeine and theophylline.
35
What compounds from grapefruit can affect drug metabolism?
* Bergamottin * Dihydroxybergamottin * Citrus furanocoumarins ## Footnote These compounds can irreversibly inhibit CYP3A4, leading to drug interactions.
36
What is the success rate of catheter ablation surgery?
90% + ## Footnote Catheter ablation is a second-line treatment for various dysrhythmias when medications fail.
37
What is the purpose of cardioversion?
Quickly restore heart to natural rhythm ## Footnote This can be done pharmacologically or electrically, often synchronized with the R wave.
38
What is the difference between defibrillation and cardioversion?
Defibrillation is non-synchronized; cardioversion is synchronized ## Footnote Defibrillation is used for pulseless ventricular tachycardia or ventricular fibrillation.
39
What is an implantable cardioverter defibrillator (ICD)?
Device placed inside the patient that monitors heart and delivers shocks ## Footnote ICDs are used to manage life-threatening dysrhythmias.
40
What are artificial pacemakers primarily used to treat?
Bradycardias and heart block ## Footnote They are often used following AV node ablation.
41
What is the connection between ether a-go-go and long QT syndrome?
EAG and hERG interactions ## Footnote Long QT syndrome can be drug-induced and is linked to hERG mutations.
42
What is a common reason for drug failure during development?
hERG interactions ## Footnote Many drugs have been withdrawn due to long QT syndrome linked to hERG.
43
Who is known for early use of cocaine in medicine?
Koller and Halsted ## Footnote Cocaine was used in dental surgery and as a safer alternative to ether and chloroform.
44
Fill in the blank: Cocaine was commonly used in the ______ century.
19th ## Footnote Cocaine had significant medical applications during this period.
45
What is the role of the AV node?
Delays the electrical impulse from the atria to the ventricles, ensuring they don’t contract simultaneously
46
What is the bundle of Kent?
An abnormal accessory pathway seen in Wolff-Parkinson-White syndrome that allows electrical signals to bypass the AV node, leading to tachycardia
47
What happens in Phase 0?
Rapid depolarisation
48
What happens in Phase1?
Brief repolarisation following depolarisation, marked by a slight outward flow of potassium ions
49
What happens in Phase 2?
The plateau phase of the cardiac AP = calcium ions enter the cell, balancing the flow of potassium
50
What happens in Phase 3?
Rapid repolarisation due to the continued outward flow of potassium ions
51
What happens in Phase 4?
Resting state of the AP = the heart is between beats, it is not a steady state in SA node cells due to the pacemaker potential
52
What is the P wave?
Represents atrial depolarisation or the electrical activity that causes atria to contract
53
What is the QRS complex?
Represents ventricular depolarisation or the electrical activity that causes ventricles to contract
54
What is the T wave?
Represents ventricular repolarisaton or the electrical recovery of the ventricles after contraction

Drugs: Molecules To Man (13 decks)

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