Electrocardiography

Question 1

describe pathway of limb lead I

Answer 1

between L and R arms

Question 2

describe pathway of limb lead II

Answer 2

along the long axis of the heart, between L foot and R arm

Question 3

describe pathway of limb lead III

Answer 3

between L foot and L arm

Question 4

Which plane are the limb leads in?

Answer 4

frontal plane

Question 5

Which plane are the augmented vector leads in?

Answer 5

frontal plane

Question 6

Which plane are the precordial/chest leads in?

Answer 6

horizontal plane

Question 7

Where are the electrodes placed for the standard limb leads?

Answer 7

L foot, L and R arms

Question 8

Where are the electrodes placed for the augmented vector leads, and how does it work?

Answer 8

positive electrodes at L foot, L and R arms

negative central terminus calculated mathematically, near centre of heart

Question 9

Where are the electrodes placed for the precordial/chest leads, and how does it work?

Answer 9

six positive electrodes placed: RA to apex, and around lateral left ribs
negative central terminus calculated mathematically, near centre of heart

Question 10

electrical event associated with P wave

Answer 10

atrial depolarization

Question 11

mechanical event occurring during P wave

Answer 11

end of diastasis

Question 12

PR interval

Answer 12

less than 200 ms

Question 13

electrical events associated with PR segment

Answer 13

atrial depolarization, impulse continues through the AV node, stops at Bundle of His

Question 14

QRS interval

Answer 14

less than 100 ms

Question 15

electrical event associated with the QRS complex

Answer 15

ventricular depolarization (bundle branches and Purkinje fibres)

Question 16

component of ECG associated with bundle branch stimulation

Answer 16

QRS complex

Question 17

component of ECG associated with atrial depolarization only

Answer 17

P wave

Question 18

component of ECG associated with atrial contraction

Answer 18

PR segment

Question 19

factors that affect QRS amplitude/height

Answer 19

directly related: muscle thickness

inversely related: body mass, pericardium (thickness and amount of fluid)

Question 20

affect of body mass on QRS amplitude

Answer 20

larger body habitus = greater distance from electrodes = poor through-energy/muffled conduction

Question 21

affect of pericardial effusion on QRS amplitude

Answer 21

more paricardial fluid = greater distance from electrodes = poor through-energy/muffled conduction

Question 22

affect of thickened pericardium on QRS amplitude

Answer 22

poor through-energy/muffled conduction

Question 23

affect of hypertrophic cardiomyopathy on QRS amplitude

Answer 23

more muscle = more impulses = more intensity

Question 24

component of ECG associated with ventricular depolarization

Answer 24

QRS complex

Question 25

component of ECG associated with Purkinje fibre stimulation

Answer 25

QRS complex

Question 26

electrical event associated with the ST segment

Answer 26

ventricular electrical plateau before repolarization, and atrial repolarization

Question 27

mechanical event occurring during QRS complex

Answer 27

atrial contraction (late filling)

Question 28

electrical event associated with the T wave

Answer 28

ventricular repolarization and atrial resting phase

Question 29

mechanical event occurring during ST segment

Answer 29

ventricular contraction

Question 30

mechanical event occurring during T wave

Answer 30

end of ventricular contraction and IVRT

Question 31

When does early filling occur on the ECG?

Answer 31

during the ventricular resting phase, in the electrical plateau between the T and the P waves

Question 32

QT interval

Answer 32

less than 440 ms

includes QRS and ST segments, QRS=100ms, systole=300ms

Question 33

ST interval

Answer 33

variable (though systole/ventricular contraction is about 300 ms)

Question 34

Which lead is used to diagnose rhythms in most echocardiography labs?

Answer 34

limb lead II