Mechanisms of Cardiac Arrhythmias Flashcards

1
Q

What causes cardiac arrhythmias?

A

They are caused by disturbances in impulse formation, impulse conduction, or both.

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2
Q

Describe the mechanism of altered automaticity.

A

Alterations in pacemaker rate that normally exist in pacemaker cells.

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3
Q

What is tachycardia?

A

HR > 100 bpm

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4
Q

What is bradycardia?

A

HR < 60 bpm

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5
Q

What are some causes of tachycardia?

A
  • Norepinephrine
  • Stimulants
  • Ischemia
  • Ventricular aneurysm
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6
Q

What are some causes of bradycardia?

A
  • Anti-arrhythmics
  • Beta blockers
  • Ca2+ antagonists
  • Digitalis
  • Barbituates
  • Ischemia
  • Aging (fibrosis)
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7
Q

What are EKG manifestations of tachycardia?

A
  • Sinus tachycardia
  • Premature atrial contraction
  • Premature ventricular contraction
  • Atrial/Ventricular tachycardia
  • Supraventricular tachycardia
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8
Q

What are EKG manifestation of bradycardia?

A

-Sinus bradycardia

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9
Q

Describe the mechanism of reentry of excitation.

A

It is the most common arrhythmia and it is caused by electric signal circling around the heart.

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10
Q

What are the 3 requirements for reentry of excitation?

A

1 - Geometry for conduction loop
2 - Slow or delayed conduction
3 - Unidirectional conduction block

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11
Q

What are some possible causes of reentry of excitation?

A
  • Ischmia
  • Infarct
  • Congenital bypass tracts (Wolf-Parkinson White)
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12
Q

Describe the mechanism of triggered activity.

A

Can occur in the atria or ventricles and are the result of Delayed Afterdepolarizations (DADs)

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13
Q

How are DADs caused?

A

They are due to elevated INTRACELLULAR [Ca2+] which is taken up by the SR. APs will cause an abnormal release of Ca2+ into the cell and it is extruded by Na/Ca exchanger. The incoming Na cause an inward current that can cause an AP if it reaches threshold.

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14
Q

What are Early Afterdepolarizations and how are they caused?

A

EADs are related to the elongation of the AP duration and it is believed to be due to abnormal activation of the inward Ca2+ current.

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15
Q

What is sinus tachycardia?

A

Fast HR caused by inspiration

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16
Q

What is sinus bradycardia?

A

Slow HR caused by expiration

17
Q

What is Wolf-Parkinson White syndrome and what can it cause?

A

Wolf-Parkinson-White is where there is a bypass that connects the RA and the RV with the characteristics of Purkinje (rapid conduction and long refractory period) -> prolonged QRS. This can lead to reentry of excitation.

18
Q

What HR levels can lead to DADs? What levels can lead to EADs?

A

Higher HR can lead to DADs

Lower HR can lead to EADs

19
Q

What are some anti-arrhytmic therapies?

A
  1. Drugs
  2. Radio-frequency ablation
  3. DC cardioversion
  4. Implantable Cardioverter-Defibrillator (ICD)