Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Y1 LSS CVS > ECG > Flashcards

ECG Flashcards

THE CONDUCTING SYSTEM: Normal durations, how recordings are obtained, Einhovens triangle, cardiac axis, systematic approach to interpretation, common abnormalities vs normal sinus rhythm PRACTICAL CARDIOVASCULAR PHYSIOLOGY: Ability to perform an ECG and recognise normal ranges, cardiac investigations

1
Q

What is the normal duration of the P wave?

A

80ms

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is the normal duration of the QRS complex and the QRS interval?

A

80-120ms

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is the normal duration of the T wave?

A

160ms

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is the normal duration of the PR segment?

A

50-120ms

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What is the normal duration of the ST segment?

A

80-120ms

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is the normal duration of the PR interval?

A

120-200ms

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What is the normal duration of the ST interval?

A

320ms

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What is the normal duration of the QT interval?

A

350-450ms

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

How is an interval measured on an ECG?

A

From the start of a wave to the end of the last letter

e.g. QT interval from start of Q to end of T

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

How is a segment measured on an ECG?

A

From the end of the wave to the start of the next

e.g. ST segment from end of S to start of T

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What does the gradient on an ECG represent?

A

Velocity of the action potential

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What does the width of a wave on an ECG represent?

A

Duration of the event

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What does the P wave represent?

A

SAN myocytes depolarise causing atrial depolarisation

Wave moves across from right to left ventricle via internodal fibres slightly towards the cathode

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What does the PR segment represent?

A

Depolarisation of the AVN

Isoelectric to delay impulse and allow ventricular filling

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What does the Q wave represent?

A

@Start of Q wave - bundle of His rapidly conducts wave of depolarisation down septum
rest of Q wave - septum depolarises away from cathode

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What does the R wave represent?

A

Ventricular depolarisaton due to Purkinje fibres that carry wave UP towards the cathode

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What does the S wave represent?

A

Purkinje fibres carry wave up myocardium for late ventricular depolarisation, moving away from the cathode

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What does the ST segment represent?

A

Depolarised ventricles produce isoelectric ECG

19
Q

What does the T wave represent?

A

Ventricular repolarisation moving towards the cathode

20
Q

How are ECG recordings obtained?

A 
3 bipolar leads that measure potential difference between the limbs
I RA to LA  - to +
II RA to LL 
III LA to LL
3 augmented limb leads 
aVF
aVL
aVR
6 chest leads
21
Q

How are augmented limb leads formed?

A

Comparison of a single +ve electrode with a combination of the other two
aVR RA-(LA+LF)
aVL LA-(LF+RA)
aVF LF-(RA+LA)

22
Q

Where are the 6 chest leads placed?

A

V1 - right 4th intercostal space, parasternal
V2 - left 4th intercostal space, parasternal
V3 - Left midway between V2 and V4
V4 - Left 5th intercostal space @ midclavicular line
V5 - Same horizontal level as V4 but along anterior axillary line
V6 - same horizontal level as V4, but along mid axillary line

23
Q

What is the systematic approach to reading and analysing an ECG, and the expected readings for a normal ECG?

A

1) Ensure it is correct recording
2) Check signal and quality of leads
3) Voltage and paper speed
4) Patient background
THEN
1) Rate and rhythm (regular R-R intervals, 60/rr interval between 60 and 100)
2)P wave and PR interval (80ms, 120-200ms)
3) QRS duration (80-100ms)
4) QRS axis (between 30° and 120°)
5) ST segment (80-120ms, not isoelectric)
6) QT interval (420ms)
7) T wave (160ms)
DOUBLE CHECK EVERYTHING

24
Q

What is Einhoven’s triangle?

A

Imaginary triangle formed by the bipolar limb leads
Used to measure movement of electrical activity away from the heart
Augmented leads measure the potential difference from centre of triangle out to each corner of triangle (LL RA LA)
Chest leads act as cathodes

25
Q

What are the lead axes angles?

A 
Centre of Einhoven's triangle is centre ∴
Lead I 0°
Lead II 60°
Lead III 120°
aVL -30°
aVF 90°
aVR -150°
26
Q

How can the cardiac axis be calculated and what does it show?

A

The mean electrical axis of the heart during ventricular depolarisation
Helps us recognise when a patient has a deviation of the cardiac axis
1) Calculate net QRS deflection for lead I and for aVF
2)Mark these on the respective axes
3)intercept perpendicular lines to get the cardiac axis vector
4) calculate cardiac axis w tan

27
Q

What is the normal direction of the cardiac axis?

A

between 0° and 90°

28
Q

What value of cardiac axis would be classed as left axis deviation and what could this be caused by?

A 
Axis lies between -90° and 0°
Left ventricular hypertrophy
Left bundle branch block
Hyperkalemia
Inferior myocardial infarction
Conditions that elevate diaphragm e.g. COPD, pregnancy, ascites, abdominal tumours
29
Q

What value of cardiac axis would be classed as right axis deviation and what could this be caused by?

A

Axis lies between +90° and 180°
Right bundle branch block
Right ventricular hypertrophy
Lateral wall myocardial infarction

30
Q

What value of cardiac axis would be classed as the indeterminant region and what could this be caused by?

A

Axis lies between -90° and -180°
Very rare
most commonly caused by leads wrong way round

31
Q

What is normal sinus rhythm?

A

each P followed by QRS wave
regular rate and normal HR
otherwise unremarkable

32
Q

How can sinus bradycardia be recognised and what can it be caused by?

A

Each P wave followed by QRS wave
regular rate, SLOW HR
Can be healthy, caused by medication or vagal stimulation

33
Q

How can sinus tachycardia be recognised and what could it be caused by?

A

Each P wave followed by a QRS wave
Regular rate, FAST HR
Often is a physiological response

34
Q

How can sinus arrhythmia be recognised?

A

Each P wave followed by a QRS wave
Rate IRREGULAR, normal -ish HR
R-R interval varies with breathing cycle

35
Q

How can atrial fibrillation be recognised?

A

Oscillating baseline - atria contracting asynchronously

Rhythm can be irregular and slow rate

36
Q

How can atrial flutter be recognised?

A

Regular saw tooth pattern in baseline of II,III, aVF
Atrial to ventricular beats at a 2:1 ratio or higher
(Saw tooth not always visible in all leads)

37
Q

How can 1st degree heart block be recognised and what could it be caused by?

A

Prolonged ST segment/interval caused by slower AV conduction
Regular rhythm 1:1 ratio of P waves to QRS complexes
Most benign heart block, but a progressive disease of ageing

38
Q

How can 2nd degree heart block Mobitz I (Wenckebach) be recognised and what could it be caused by?

A

Gradual prolongation of the PR interval until beat skipped
Most P waves followed by QRS, some not
Regularly irregular
Caused by diseased AV node

39
Q

How can 2nd degree heart block Mobitz II be recognised?

A

Regular P waves, only some followed by QRS
No PR prolongation like in Mobitz I
Regularly irregular
Can rapidly deteriorate into 3rd degree heart block

40
Q

How can 3rd degree heart block be recognised?

A

P waves regular, QRS regular, but no relationship
P waves can be hidden by bigger vectors
Truly non-sinus rhythm

41
Q

How can ventricular tachycardia be recognised?

A

P waves hidden - dissociated atrial rhythm
Rate regular and fast
High risk of deteriorating into fibrillation
Shockable rhythm

42
Q

How can ventricular fibrillation be recognised?

A

Irregular HR 250bpm and above
Heart unable to generate an output
Cardiac arrest
Shockable rhythm

43
Q

How can ST elevation be recognised and what can it be caused by?

A

P waves visible and always followed by QRS
Rhythm regular, rate normal
ST segment elevated >2mm above isoelectric line
Caused by infarction (tissue death due to hypoperfusion)

44
Q

How can ST depression be recognised and what can it be caused by?

A

P waves visible and always followed by QRS
Regular rhythm, normal rate
ST segment depressed >2mm below isoelectric line
Caused by myocardial ischaemia (coronary insufficiency)

Y1 LSS CVS (8 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions