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CVS > 14. ECG - Identifying Some Basic Disturbances of Rhythm > Flashcards

14. ECG - Identifying Some Basic Disturbances of Rhythm Flashcards

1
Q

What is bradycardia and tachycardia?

A

Bradycardia - heart rate < 60

Tachycardia - heart rate > 100

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2
Q

What are the supraventricular arrhythmias?

A
  • Atrial fibrillation
  • Atrial flutter
  • Atrio-ventricular nodal re-entrant tachycardia (AVNRT)
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3
Q

What are the ventricular arrhythmias?

A
  • Ventricular fibrillation

* Ventricular tachycardia

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4
Q

Which of the 2 types of arrhythmias are the most dangerous?

A
  • Ventricular arrhythmias

* Atria are not as essential to sustain life, ventricles are

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5
Q

What happens on the ECG if you have problems with coronary arteries (give an example)?

A
  • S-T segment can shift up or down

* Myocardial Infarction results in S-T segment elevation

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6
Q

What happens with people born with long QT syndrome?

A

Predisposed to arrhythmias and sudden cardiac death

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7
Q

What is the standard sweep speed of an ECG?

A

25mm/s

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8
Q 
What are the normal values of the following:
• P wave
• PR interval
• Q wave
• QRS complex
• QT interval
• ST segment
• T wave
A
  • P wave - < 0.11s; < 2.5mm (Lead II)
  • PR interval - 0.12 - 0.20s
  • Q wave - < 0.04s; < 25% of total QRS complex amplitude
  • QRS complex - <0.12s; < 25mm (V6)
  • QT interval - 0.38 - 0.42s
  • ST segment - should be isoelectric
  • T wave - may be inverted in Lead III, aVR, V1 & V2 without being abnormal
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9
Q

What does a prolonged PR interval indicate?

A

Abnormal conduction in the ventricles

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10
Q

What could a large amplitude in the QRS complex indicate?

A

Ventricular hypertrophy

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11
Q

What changes on the ECG during Myocardial Ischaemia?

A

ST segment

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12
Q

What is Sinus Tachycardia?

A
  • Abnormally fast resting heart rate (100-200 bpm)
  • Comes from the sinus node
  • Normal form of waves
  • Often physiological (response)
  • Very common
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13
Q

What is Atrial Fibrillation?

A
  • Irregular beat
  • Pattern of the (irregular) beat is irregular
  • Normal QRS complex
  • Inconsistent duration between QRS complexes
  • No P waves (due to no synchronous atrial contraction)
  • Wobbling baseline due to myocardium contracting at different times
  • Atria - 350-650 bpm
  • Ventricles - 100-180 bpm
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14
Q

What is Atrial Flutter?

A
  • Saw-tooth appearance of P wave with no isoelectric line - constant atrial activity
  • This constant activity distinguishes it from atrial fibrillation
  • Some of the atrial depolarisation is conducted down to the ventricles (around every 3rd atrial beat)
  • This shows the AV node is still doing is job - protecting the ventricles from beating too fast (atrioventricular block)
  • Normal QRS
  • ST segment and T wave would look normal, but they are buried under the waves of atrial depolarisation
  • Atria - 250-350 bpm
  • Ventricles - 150 bpm (2:1 atrioventricular block)
  • Regular ventricular rhythm
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15
Q

What is Supraventricular Tachycardia (SVT)? (2 types)

A

• Atrioventricular Nodal Reentrant Tachycardia (AVNRT)
- depolarisation is rotating within the AV node
- simultaneous depolarisation of the atria and ventricles
- lots of (regular) QRS complexes
- no clear P waves - buried within QRS complexes
- re-entrant circuit within the AV node
- adenosine responsive (medication can block the AV node)
• Atrioventricular Reentrant Tachycardia (AVRT) - circuit within the atrium and ventricle
- re-entrant circuit through accessory pathways

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16
Q

What is Pre-excitation Syndrome?

A
  • AV node usually makes sure that only rates below 200 bpm get to the ventricles
  • Some people born with an accessory pathway (congenital connection)
  • Atrial conduction can’t be controlled
  • No isoelectric PR segment and it’s abnormally short (<0.12s)
  • Delta wave - slurred QRS upstroke due to activation via accessory pathway, rapid upstroke in the second segment due to activation via the normal route
17
Q

What is Wolff-Parkinson-White Syndrome?

A
  • Accessory pathway leading to ventricular pre-excitation
  • Short PR interval
  • Delta wave
  • Predisposes to AVRT - conduction comes down one way and back up the other making a loop
  • 1/3 conduct antegradely (WPW) - downwards
  • 2/3 conduct retrogradely (concealed pathways) - upwards
18
Q

What is the treatment for Wolff-Parkinson-White Syndrome?

A

Radio frequency ablation to burn away the accessory pathway

19
Q

What is a 1st Degree AV Nodal Block?

A
  • Type of Bradyarrhythmia
  • Long PR (by around 2x) due to long pause between atria and ventricles contracting
  • Still 1 P wave associated with 1 QRS complex
  • Largely asymptomatic
20
Q

What is a 2nd Degree AV Nodal Block (2 types)?

A

• Type of Bradyarrhythmia
• Some beats do not get conducted from the atria to the ventricles
• Some P waves are no followed by QRS complexes
• Mobitz Type 1 (Wenckebach)
- gradual prolongation of the PR interval culminating in a single dropped beat
- PR interval gradually gets longer until the AV node can’t cope and blocks conduction - mixed QRS complex
• Mobitz Type 2
- dropped beats but no pattern of gradual prolongation of the PR interval
- fixed PR intervals, then a dropped beat
- 2:1 = every other P wave isn’t followed by a QRS complex
- probably symptomatic and treatment involves fixing a pacemaker

21
Q

What is a 3rd Degree AV Nodal Block?

A
  • Type of Bradyarrhythmia
  • AV node doesn’t function
  • No conduction from the atria to the ventricles
  • Ventricles start firing on their own
  • P waves and QRS complexes are completely dissociated
  • May occur at regular intervals but fire independently of each other
  • AV dissociation on ECG signifies a complete heart block
22
Q

What do Bundle Branch Blocks result in?

A

• If the block is in the right bundle branch, conduction only goes down the left and spreads slowly across the myocardium (from left side to right side)
• Depolarisation has to spread slowly from the left side to the right side
• QRS complex widens (> 0.12s) (bunny ears often seen with first smaller than second)
• QRS morphology changes (depending on ECG (chest) lead and if it is a right or left bundle branch block)
(• QRS complex is the time taken for all ventricular myocytes to be depolarised)

23
Q

How do you distinguish between a Right and Left Bundle Branch Block?

A

• Left - wide QRS complex with unique shape in leads overlying the right ventricle
- V1 = W
- V6 = M (bunny ears)
• Right - wide QRS complex with unique shape in leads overlying the left ventricle
- V1 = M (bunny ears)
- V2 = W

24
Q

What is Ventricular Tachyarrhythmia?

A
  • Fatal
  • Rapid, regular, broad QRS complex pattern
  • Rapidness can cause light headedness or passing out
  • Can become ventricular fibrillation if left for long
25
Q

What is Ventricular Fibrillation?

A
  • Broad, irregular QRS complexes
  • No pattern
  • Defibrillator needed to try and fix the irregular contraction
  • High heart rate

CVS (21 decks)

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