ECGs Flashcards
What position must patient be in to perform an ECG?
Lying on bed at 30-40 degrees with one or two pillows supporting neck
Electrodes should be applied over bone or muscle to limit interference?
Bone
Explain placement of the limb electrodes?
RA = red LA = yellow LL = green RL = black (earthed)
Ride, your, green, bike (clockwise starting at right hand)
Explain placement of chest electrodes?
V1 - 4th ICS on right
V2 - 4th ICS on left
V3 - midway between V2 and V4
V4- 5th ICS midclavicular line
V5- same level as V4 anterior axillary line
V6 - same level as V4 and 5, mid axillary line
1 large box on an ECG is worth?
0.2 seconds (200 ms)
5 large boxes on an ECG are worth?
1 second
1 small box on an ECG is worth?
0.04 seconds (40 ms)
How do you calculate rate on an ECG?
Regular - large number of squares between 2R waves and divide into 300
Irregular - count the number of QRS complexes in 6 seconds
Lead 1 is positive and AVF is positive?
Normal axis
Lead 1 is positive and AVF is negative?
left axis
Lead 1 is negative, AVF is positive?
Right axis
Lead 1 is negative and AVF is negative?
Indeterminate axis
Define the PR interval and give normal length?
onset of P to onset of QRS, represents AV node delay, normal if 120-200 ms (3-5 small squares)
you should look at it and ask does the PR measure 1 big square or less
What is normal length of QRS?
120 ms or less (3 small boxes or less)
Define the QT interval and give normal length?
Start of QRS until end of T wave - 8-12 small boxes (varies a lot though and there can be formulas to work out what should be normal
Define a supra ventricular rhythm and list some examples
Supraventricular rhythms - originate above the AV node whether conducted through it or not
E.g. Sinus rhythm, sinus arrhythmia, AF, atrial flutter, AVNRT (WPW), wandering atrial pacemaker, SVT/ AVNRT
ECG meets all the criteria of sinus rhythm but the rhythm itself is irregular, the irregularity is caused by physiological changes in the cardiac timing caused by respiration, it is considered a normal variant
Sinus arrhythmia
Disorganised electrical activity in the atria, irregularly irregular QRS complexes and absent P waves
Atrial Fibrillation
Regular usually narrow complex tachycardia, saw tooth baseline, F waves, regular QRS complexes, rate divisible into 300
Atrial flutter
Rhythm originates at the AV junction, retrograde p waves can be seen, normal QRS morphology
Junctional rhythm
Sinus rhythm with differing morphologies of P waves on beats
Supraventricular ectopics
Define ventricular rhythms? are they ever normal? give some examples?
rhythms that originate in the ventricle - always pathological, always broad complexes QRS > 120 ms
E.g. ventricular premature complexes, ventricular tachycardia (monomorphic), polymorphic ventricular tachycardia (torsades de pointes), ventricular escape rhythm, ventricular fibrillation
Regular broad complex tachycardia with QRS > 120 ms
Ventricular tachycardia
What is torsades de pointes and what is it often associated with?
Polymorphic VT often associated with long QT interval and R on T phenomenon
Irregular random baseline with no discernible waveforms
VF
Define heart block?
Term given to a block in conduction between the atria and ventricle
Not to be confused with bundle branch block
Due to AV nodal dysfunction (drugs, ischaemia, age)
Define first degree heart block?
PR interval > 200 ms, no progressive lengthening, stable rhythm
Define Mobitz 1 second degree heart block?
mobitz 1 - progressive PR prolongation until a missed beat - not treated unless severe or HD compromise
Define mobitz 2 second degree heart block?
constant PR interval but every nth beat is dropped - always abnormal
Define 3rd degree heart block?
no relationship between P wave and QRS
Lateral leads?
1, AVL, V5, V6
Inferior leads?
2,3 and AVF
Anterior leads?
V1 V2 V3 V4
ST elevation?
More than 1mm in 2 contiguous limb leads
More than 2mm in two contiguous limb leads
contiguous = leads next to each other
Evolution of ST changes in MI?
Normal > Peaked t wave > ST segment elevation that gradually increases > Q wave formation and loss of R wave > T wave inversion
What is pericardial inflammation usually secondary to?
MI or Viral infection
Symptoms of pericarditis?
- Pleuritic chest pain (worst on inspiration)
- Fever
- Pericardial friction rub
ECG changes in pericarditis?
- Upward concave ST elevation
- Changes do not evolve (unlike MI)
- Widespread changes involving > 1 vascular territory e.g. inferior and anterior ST elevation
- Can be difficult to differentiate from ST elevation MI
- PR Depression is a useful diagnostic tool
How is ventricular hypertrophy shown on ECG?
increased height of QRS complexes
Left bundle branch block will be shown in ?
V5 and V6
QRS will be more than 0.12 secs
Right bundle branch block will be shown in ?
V1 and V2
QRS will be more than 0.12 secs
