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LSS Cadiovascular System > practical cardiovascular physiology > Flashcards

practical cardiovascular physiology Flashcards

electrocardiogram (ECG): demonstrate ability to perform an ECG and recognise normal ranges

1
Q

normal duration of P wave

A

80ms

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2
Q

normal duration of R wave (QRS complex)

A

80-120ms

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3
Q

normal duration of T wave

A

160 ms

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4
Q

normal duration of of PR segment

A

50-120ms

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5
Q

normal duration of ST interval

A

320ms

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6
Q

normal duration of QT interval

A

350-450ms

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7
Q

horizontal: how many seconds does 5mm (5 squares) on an ECG correspond to

A

0.2 seconds

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8
Q

vertical: how many mV dows 5mm (5 squares) on an ECG correspond to

A

0.5mV

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9
Q

what does an upward deflection denote

A

wave of depolarisation towards cathode (+) or repolarisation away from cathode (+)

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10
Q

what does a downward deflection denote

A

wave of depolarisation towards anode (-) or repolarisation away from anode (-)

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11
Q

what is the gradient equal to

A

velocity of action potential

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12
Q

what is the width equal to

A

duration of event

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13
Q

what happens during P wave

A

SAN autorhythmic myocytes depolarise, causing P-wave and atrial depolarisation, with wave moving across from right to left ventricle via internodal fibres, and slightly towards cathode

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14
Q

what happens in the PR segment

A

AVN depolarises in PR segment and is isoelectric as delayed impulse allowing for ventricular filling

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15
Q

what happens during Q wave: isoelectric section

A

isoelectric as bundle of His rapidly conducts wave of depolarisation down septum

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16
Q

what happens during Q wave

A

septum depolarises away from cathode

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17
Q

what happens during R wave

A

ventricular depolarisation due to Purkinje fibres, with wave spreading towards cathode

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18
Q

what happens during S wave

A

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

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19
Q

what happens during ST segment

A

depolarised ventricles produce an isoelectric ECG

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20
Q

what happens during T wave

A

ventricular repolarisation moving towards cathode

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21
Q

what happens during the U wave (may not be obeserved as small size)

A

Purkinje fibre repolarisation towards cathode

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22
Q

what are electrodes

A

conductive material in contact with skin

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23
Q

what do cables/wires attach to

A

electrodes

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24
Q

why is conductive gel put on electrode and arm before ECG

A

human body not particularly good at conducting

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25
Q

where are the 4 limb leads placed

A

right arm, left arm, left leg, right leg

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26
Q

what are the chest leads

A

V1-V6

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27
Q

where is V1 placed

A

4th intercostal, right sternal border

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28
Q

where is V2 placed

A

4th intercostal, left sternal border

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29
Q

where is V3 placed

A

in-between V2 and V4 (on top of 5th rib)

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30
Q

where is V4 placed

A

5th intercostal, mid-clavicular line

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31
Q

where is V5 placed

A

5th intercostal, anterior axillary line (usually halfway between V4 and V6)

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32
Q

where is V6 placed

A

5th intercostal, mid-axillary line

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33
Q

what is the speed an ECG runs at

A

25mm/sec

34
Q

what is Einthoven’s triangle

A

imaginary formation of three limb leads in triangle, formed by arms and legs, forming inverted equilateral triangle with heart at centre, producing zero potential when voltages summed

35
Q

what is limb lead I from

A

right arm to left arm

36
Q

what is limb lead II from

A

right arm to left leg - normal ECG lead

37
Q

what is limb lead III from

A

left arm to left leg

38
Q

what plane does Einthoven’s triangle use to measure movement of electricity away from heart

A

coronal

39
Q

why are limb leads I, II and III bipolar

A

have physical anodes and cathodes

40
Q

in bipolar leads, what is a net deflection equal to

A

sum of net deflections in other 2 leads

41
Q

what are the unipolar leads (and midpoint of which limb leads)

A

aVF (limb lead I), aVL (limb lead II), aVR (limb lead III)

42
Q

what do unipolar leads measure potential difference between

A

null point with relative 0 potential at centre of triangle (midpoint between two limb electrodes)

43
Q

what do precordial leads use as cathodes and measure

A

chest leads, so measure electrical activity flowing from heart towards chest leads

44
Q

what 3 cardiac arteries are involved with ECG and what heart position do they correlate to

A

left circumflex (LCx) - lateral, right coronary (RCA) - inferior or anterior, left anterior descending (LAD) - septal

45
Q

lead I: heart region, artery, cathode, anode

A

lateral, LCx, left arm, right arm

46
Q

lead II: heart region, artery, cathode, anode

A

inferior, RCA, left leg, right arm

47
Q

lead III: heart region, artery, cathode, anode

A

inferior, RCA, left leg, left arm

48
Q

aVR: heart region, artery, cathode, anode

A

n/a, n/a, right arm, halfway between leg arm and left leg

49
Q

aVL: heart region, artery, cathode, anode

A

lateral, LCx, left arm, halfway between right arm and left leg

50
Q

aVF: heart region, artery, cathode, anode

A

inferior, RCA, left leg, halfway between right arm and left arm

51
Q

V1: heart region, artery, cathode, anode

A

septal, LAD, V1, heart

52
Q

V2: heart region, artery, cathode, anode

A

septal, LAD, V2, heart

53
Q

V3: heart region, artery, cathode, anode

A

anterior, RCA, V3, heart

54
Q

V4: heart region, artery, cathode, anode

A

anterior, RCA, V4, heart

55
Q

V5: heart region, artery, cathode, anode

A

lateral, LCx, V5, heart

56
Q

V6: heart region, artery, cathode, anode

A

lateral, LCx, V6, heart

57
Q

what is the axis of a wave or complex

A

direction wave of depolarisation is moving in on coronal plane (not using precordial leads)

58
Q

what is the normal cardiac axis

A

-30 to +120

59
Q

lead I axis

A

0

60
Q

lead II axis

A

60

61
Q

lead III axis

A

120

62
Q

aVL axis

A

-30

63
Q

aVF axis

A

90

64
Q

aVR axis

A

-150

65
Q

diagram of leads and axis

A

benjis

66
Q

how do you calculate the axis

A

select 2 leads at 90 degrees, work out net QRS depolarisation on each lead, form triangle by drawing x mm along numerical lead, and y mm perpendicular from lead, take theta as tan^-1 ( augmented lead net depolarisation (y)/numerical lead net depolarisation (x)); cardiac axis = numerical lead axis - theta

67
Q

axis and corresponding ECG

A

benjis

68
Q

systematic approach to interpretation

A

correct recording → signal quality and leads → voltage and paper speed → patient background (CVS/resp disease as axis moves on COPD) → heart rate (300/no. big squares) → durations of P, PR, QRS, ST, QT, T → QRS axis

69
Q

features of sinus rhythm

A

Ps followed by QRS 1:1; regular rate and normal; otherwise unremarkable

70
Q

features of sinus bradychardia

A

Ps followed by QRS 1:1; regular rate and slow; can be healthy/medication/vagal stimulation

71
Q

features of sinus tachycardia

A

Ps followed by QRS 1:1; regular rate and fast; often physiological or decreased venous return

72
Q

features of sinus arrhythmia

A

Ps followed by QRS 1:1; irregular rate and normal-ish rate; R-R varies with breathing

73
Q

features of atrial fibrillation

A

oscillating baseline so asynchronous atria contraction; irregular and slow rhythm; turbulent flow pattern increases clot risk

74
Q

features of atrial flutter

A

regular saw-tooth pattern in baseline on II, III, aVF; atrial:ventricular beats 2:1, 3:1 or higher; not visible in all leads as some flutters hidden in QRS complex

75
Q

features of 1st degree heart block

A

prolonged PR due to slower AV conduction; regular rhythm of P:QRS; mostly benign

76
Q

features of 2nd degree heart block (Mobitz 1)

A

increasing PR until missed QRS; regularly irregular due to diseased AVN; Wenckebach

77
Q

feaures of 2nd degree heart block (Mobitz 2)

A

no PR elongation and some QRS complexes missed; regularly ireregular with fixed ratio of successes to failures (e.g. 2:1); can rapidly deteriorate to 3rd degree

78
Q

features of 3rd degree heart block

A

regular P waves and QRS complexes but no relationship; AVN/myocardium can be auto-rhythmic; non-sinus with backup pacemakers; P waves regular and fast, QRS regular and slow

79
Q

features of ventricular tachycardia

A

P waves hidden in dissociated atrial rhythms; ventricles beating rapidly and very hard; rate regular and fast; risk of deterioration to ventricular fibrillation; shockable rhythm; all vectors look the same

80
Q

features of ventricular fibrillation

A

heart rate irregular and >250bpm; no output; shockable; vectors will change and don’t all look the same

81
Q

features of ST elevation

A

P waves visible and followed by QRS; regular normal rate; ST-segment elevated >2mm above isoelectric; caused by infarction

82
Q

features of ST depression

A

P waves visible and followed by QRS; regular normal rate; ST-segment depessed >2mm below isoelectric; caused by ischaemia

LSS Cadiovascular System (40 decks)

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