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PHAR20300 > CARDIAC CONDUCTION > Flashcards

CARDIAC CONDUCTION Flashcards

1
Q

How does an electrocardiogram ( ECG) work?

A

Detects very small differences in electrical potential at two points in the body due to movement of cellular depolarisation along the axis of measurement points

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2
Q

How many electrodes are placed on the skin in an ECG?

A
  • 10 electrodes (6 around the heart + 4 on the extremities)
  • one electrode acts as +ve and the other acts as -ve = difference gives us the lead
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3
Q

How many leads are measured in an ECG and what is the relevance of a lead?

A

12 - each lead gives a different electrical picture of the heart

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4
Q

What does a P wave show?

A

Atrial depolarisation

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5
Q

What does the QRS complex show?

A

Ventricular contraction (or ventricular depolarization)

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6
Q

What does a T wave show?

A

Ventricular repolarisation

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7
Q

What does the QT interval show?

A

Duration of the action potential

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8
Q

What does the ST segment show?

A

The plateau phase of the action potential (after ventricles have depolarized)

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9
Q

What does the R-R interval show?

A

Time between heartbeats

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10
Q

What does amplitude (height) of an ECG wave represent?

A

Height of waves - is directly proportional to the mass of the cardiac tissue generating it

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11
Q

What does the shape of an ECG wave depend on?

A

Type of electrode and the direction

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12
Q

How to measure heart rate?

A
  • 300 ÷ by the number of large boxes between two R waves (ONLY FOR regular rhythm) - For irregular rhythms – 10 x number of R waves in 6 seconds
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13
Q

What factors must one look at to analyse the ECG?

A
  • Identify QRS complex (ventricular contraction)
  • Heart rate
  • Heart rhythm
  • P waves
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14
Q

When decides whether there is conduction problems above ventricles (supraventricular e.g. SA/AV node or atria), what factors should you look at?

A
  • P wave
  • PR interval
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15
Q

If the P wave’s shape is altered, what does this represent?

A

AVN block

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16
Q

If the PR interval is too long, what does this represent?

A

AV Block

17
Q

If the PR interval is too short, what does this represent?

A

Wolff-Parkinson-White syndrome

18
Q

When decides whether there is conduction problems in ventricle (ventricular arrhythmia), what factors should you look at?

A
  • QRS interval
  • QT interval
19
Q

If the QRS interval is deep & wide, what does it represent?

A

Myocardial infraction

20
Q

If the QRS interval is notched, what does it represent?

A

Right or left bundle block

21
Q

If the QT interval is prolonged, what does it represent?

A

Failure to repolarise quickly enough (long refractory period)

22
Q

If the QT interval is shortened, what does it represent?

A

Repolarisation too fast (short refractory period)

23
Q

What are different types of irregular rhythms?

A
  • Regularly irregular - recurrent pattern of irregularity
  • Irregularly irregular - (i.e. completely disorganised
24
Q

What is sinus tachycardia and sinus bradycardia?

A

Rhythm is regularly irregular; however, it is too fast or slow

25
Q

What does no P wave in an ECG possibly signify?

A

Atrial fibrillation as atrial myocytes are ectopic pacemakers (not the SA node)

26
Q

What condition produces an irregularly irregular ECG pattern?

A

Ventricular fibrillation - ectopic signals from many foci cause sections of ventricles to contract independently (no pattern)

27
Q

What condition causes a gradual change in amplitude and a twisting of the QRS complex?

A

Torsade de Pointes

28
Q

What does a long P-Q interval possibly signify?

A

First degree heart block (AV block) - conduction through AV node slowed

29
Q

What does missed QRS complexes (ventricular beats) signify?

A

Second-degree heart block - some impulses don’t go through AVN = no ventricles depolarisation

30
Q

What condition causes the P wave to be absent or disconnected from QRS?

A

Third-degree heart block - AVN doesn’t produce any impulses

31
Q

What is a STEMI?

A

A myocardial infarction that has ST elevation (but can occur without MI)

PHAR20300 (25 decks)

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