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CARDIOLOGY PHYSIOLOGY > Electrocardiogram - ECG > Flashcards

Electrocardiogram - ECG Flashcards

1
Q

How can an ECG be recorded?

A
  1. Active or exploring electrode connected to an indifferent electrode at zero potential (unipolar recording).
  2. Two active electrodes - bipolar reading.
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2
Q

How can Einthoven’s triangle be approximated?

A

Using the standard limb leads:
1. Electrode left arm.
2. Electrode right arm.
3. Electrode left leg.

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3
Q

What causes a positive deflection in an ECG?

A

Depolarisation moving towards an active electrode.

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4
Q

What causes a negative deflection in an ECG?

A

Depolarisation moving in the opposite directin from an active elctrode.

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5
Q

What produces the P wave?

A

Atrial depolarisation.

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6
Q

What produces the QRS complex?

A

Ventricular depolarisation.

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7
Q

What produces the T wave?

A

Ventricular repolarisation.

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8
Q

What are the bipolar leads?

A

Standard limb leads - I, II, III.

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9
Q

What doe the bipolar leads record?

A

Differences in potential between the two limbs.

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10
Q

Where are the electrodes in lead 1?

A

Left arm and right arm - an upward deflection is due to the left arm becoming positive relative to the right (left arm positive).

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11
Q

Where are the elctrodes in lead II?

A

Right arm and left leg - left leg is positive.

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12
Q

Where are the elctrodes in lead III?

A

Left arm and left leg - left leg is positive.

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13
Q

How many unipolar leads are there?

A

9.

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14
Q

What do the unipolar leads record?

A

Potential difference between an exploring electrode and an indifferent electrode.

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15
Q

What are the unipolar chest leads?

A

Precordial leads - V1-V6.

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16
Q

What are the unipolar limb leads?

A

Augmented limb leads:
1. aVR - right arm.
2. aVL - left arm.
3. aVF - left foot.

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17
Q

What do augmented limb leads record?

A

Between one limb and the other two limbs.

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18
Q

What happens during a PR interval?

A

Atrial depolarisation and conduction through the AV node.

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19
Q

How long is the PR interval?

A

0.12-0.2 seconds.

20
Q

What happens during the ARS complex?

A

Ventricular depolarisation and atrial repolarisaiton.

21
Q

How long is the QRS duration?

A

0.08-0.1 seconds.

22
Q

What happens during the QT interval?

A

Ventricular depolarisation and repolarisation.

23
Q

How long is the QT interval?

A

400 - 430 msec / 0.4-0.43 seconds.

24
Q

What happens during the ST interval?

A

Ventricular repolarisation - during T wave.

25
Q

Where are atria located in the chest?

A

Posteriorly.

26
Q

Where are ventricles located in the heart - anatomical?

A

Form the base and anterior surface of the heart.

27
Q

Where is the RV and LV?

A

RV is anterolateral to the left.

28
Q

What does the aVR lead look at?

A

Cavities of the ventricles.

29
Q

What moves away from aVR?

A
  1. Ventricular depolarisation.
  2. Atrial depolarisation.
  3. Ventricular repolarisation.
30
Q

What has negative deflections in aVR?

A
  1. P wave - atrial depolarisation.
  2. QRS complex - ventricular depolarisation.
  3. T wave - ventricular repolarisation.
31
Q

What do aVL and aVF lead look at?

A

The ventricles.

32
Q

What on the ECG has positive deflections in aVF and aVL?

A

P wave, QRS and T wave.

33
Q

What leads don’t have Q waves?

A

V1-2 - initial portion of the QRS complex is a small upward deflection due to ventricular depolarisation firstly moving across the midportion of the septum from left to right toward the exploring electrode. The wvae of excitation goes down the septum into LV and away from the electrode - produces large S wave. Goes back along the ventricular wall toward to electrode - return back to isoelectric line.

34
Q

What leads have small Q waves?

A

V4-V6 - left to right septal depolarisation and large R wave (septal and LV depolarisation).

35
Q

What does the deflection in each lead indicate?

A

Magnitude and direction in the axis of the lead of the electromotive force generated in the heart (cardiac axis).

36
Q

What is the mean QRS axis?

A

-30 to +110 degrees.

37
Q

What is left axis deviation?

A

Axis is to the left of -30 degrees.

38
Q

What is right axis deviation?

A

Axis is to the right of +110 degrees.

39
Q

What can cause right axis deviation?

A
  1. Right ventricular hypertrophy.
  2. Acute right ventricular strain e.g. PE.
  3. Lateral STEMI.
  4. COPD.
  5. Hyperkalaemia.
  6. Wolff-parkinson white.
40
Q

What can cause left axis deviation?

A
  1. Left ventricular hypertrophy.
  2. Left bundle branch block.
  3. Inferior MI.
  4. ventricular pacing/ectopy.
  5. Left anterior fascicular block.
41
Q

What leads to look at to determine axis?

A
  1. Lead 1.
  2. Lead 2.
42
Q

When determining the axis what do you look at?

A

QRS complex - need to see if it is positive, equiphasic or negative.

43
Q

What does a positive QRS mean?

A

R wave > S wave.

44
Q

What does it mean if both QRS complexes are positive in both lead 1 and aVF?

A

Normal axis - the quadrant of both combines and its in the lower right quadrant which is normal.

45
Q

What does it mean if QRS lead 1 is positive and QRS aVF is negative?

A

Possible LAD - upper right quadrant.

46
Q

What does it mean if QRS lead 1 is negative and QRS aVF is positive?

A

Right axis deviation.

47
Q

What does it mean if QRS lead 1 is negative and QRS aVF is negative?

A

Extreme axis deviation.

CARDIOLOGY PHYSIOLOGY (4 decks)

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