Cardiology - ECG Flashcards
Which part of the ECG is always down
Q
Which part of the ECG is always up
R
What part of the ECG represents dead myocardium
Q waves
Determining the rate - ECG
300/no’ large squares
How many QRS in 10s
Determining the rhythm ECG
Sinus - Each P wave = followed by QRS
Constant PR interval
Normal cardiac axis
I + II = +ve
RAD
I negative
III positive
LAD
II + III negative
P wave appearance RAH
Peaked/tall
P wave appearance LAH
Notched/broad
Def PR interval
Time from beginning of P wave to beginning of QRS
Normal range PR interval
0.12 - 0.2
Or
3-5 small squares
What does prolonged PR interval indicate
1st degree heart block
What does a wide QRS indicate
Bundle branch block
Tall R waves in V1 indicate
RVH
Tall R waves V6 indicate
LVH
2 conditions –> ST elevation (2)
MI
Pericarditis
2 conditions –> ST depression
Ischaemia
Digoxin
In what leads is T wave inversion considered normal
aVR
III
V1/2
Where can Q waves be normal
I
VL
V5/6
Def QT interval
From beginning of QRS to end of T wave
Normal value QT interval
<0.45 s
Or 2 large squares
What is a sinus rhythm
When electrical activity starts in SAN
Hence P wave
What is a normal axis
-30 –> +90
Conditions –> R axis deviation (10)
Infancy PE Cor pulmonale ASD seculum rvh RBBB L post hemiblock Dextrocardia LV ectopic rhythm Congenital heart disease
Conditions –> L axis deviation (7)
L ant hemi block LVH WPW syndrome RV ectopic beats Mechanical shift Normal ASD primum
Hyperkalaemia ECG
Tall tented T waves
More PQT waves
Hypokalaemia ECG
Flatter T waves
Def bradycardia
<40-60bpm
Def tachycardia
> 120 bpm
Def S wave
Any deflection below baseline following R wave
Narrow QRS complexes originate from
Above AVN
Wide QRS complexes are often x in origin
Ventricular
examples of conditions –> T wave inversion
Ischaemia
Ventricular hypertrophy BBBB
Digoxin - sloped ST segments
What is meant be: ST segment should be isoelectric
The same level apart between the T wave and the next P wave
J point
Between end of QRS complex and start of T wave
What is re-entry tachycardia
Impulse –> depolarisation twice in a row at faster rate than norm
= 180-200bpm
Why does re-entry tachycardia occur
Nodal re-entry pathways within AVN
What is WPW syndrome
Accessory pathway allows electrical signal from ventricles to enter atria –> earlier than norm contraction
–> repeated stim of AVN
What is sinus arrhythmia
HR varies between 40-120
Due to irreg discharge SAN
Most common cause sinus arrhythmia
Breathing
Due to fluctuations in vagal tone
What is Atrial ectopic?
Premature discharge of ectopic atrial focus
Appearance ECG atrial ectopic
P wave shape different
Occurs early before next P wave due
What are supraventricular ectopics
Ectopic beats originating in AVN or atria
What do patients with atrial ectopics complain of
Skipped beat or irreg pulse
What condition can atrial ectopics lead to
AF
Causes AF
use PIRATES PE IHD/Idopathic Rheumatic valve disease Anaemia/alcohol/age Thyroid (hyper) Elevated BP Sleep apnoea/sepsis
ECG appearance AF
Irreg baseline
no P waves
Irreg QRS rate
How many atrial contractions /min in AF
450-600
What is atrial flutter
Atrial rate >250 and no flat baseline between P waves
Appearance ECG atrial flutter
Saw toothed baseline
diff between AF and atrial flutter
Similar than in both - normal coordination of atria is lost
But in flutter, there is some element of synchronicity
Appearance ventricular ectopic ECG
Broad QRS
Possible inverted P waves
Bigeminy
Appearance ventricular tachycardia ECG
Broad abnormal QRS in all 12 leads
HR > 100bpm
Torsades de Pointes
In VT which signs indicate immediate electrical cardioversion (4)
BP <90mmHg
Chest pain
HF
Rate >150
In VT, in abscence of signs indicating ECV, what Mx should be done
300mg loading dose amiodarone over 30 mins
What is VF?
Individual mm fibres can’t contract independently, hence = fibrillating –> no cardiac output
VF ECG appearance
No QRS
ECG totally disorganised
What is branch block?
Depolarisation reaches septum normally (norm pR interval)
But abnormal condition through L/R bundle branches of his –> Wide QRS
Right bundle branch block
IV septum depolarised from Left normal Hence R wave V1 + small Q V6 Later R depolarisation --> 2nd R wave Excitation LV --> S wave V1 + R in V6 RV depolarises after L --> R' V1 and deep S wave
Which lead is RBBB best seen in?
V1
MarroW - M shape V1
W shape V6
Left bundle branch block
Septum depolarises from R–>L
Hence Q wave V1 R wave V6
RV depol before LV –> small R V1 and S in V6
Subsequent LV depol –> S wave V1 + S wave V6
Also assoc w/ T wave inversion Lateral leads
Which lead is LBBB best seen in?
V6
WilliaM - W shape V1
M shape V6
If LBBB is asymp - what condition should be considered
Aortic stenosis
If LBBB is associated with chest pain, what condition should be considered
acute MI
What is a hemiblock?
LB divides into ant and posterior fascicles
= hemi block if 1 fasicle blocked
Left anterior block - ECG changes
Upward + leftward directoin
Hence LAD >-45’
Rs complex lead III
Left posterior block - ECG changes
Bulk depolarisation downward and to right
RAD +>120
S wave I
q wave III
Why does QRS not widen in hemiblocks
Because other fascile is intact
Causes hemiblocks (4)
Acute MI
Coronary aa disease
HTN
Congenital heart disease + cardiomyopathies
What is the voltage criteria for LVH?
Combined height R wave in V5/6 + depth S wave V1 should not exceed 25mm
What is heart block
Abnormal conduction from SAN to ventricles
PR interval 1st degree heart block
> 0.22s
What is 1st deg heartblock
Each wave SAN depolarisation = spread to ventricles
But = delay somewhere along pathway
What can 1st degree heart block indicate? (4)
CAD
Acute rheumatic fever
Electrolyte disturbance
Digoxin toxicity
What is Sinoatrial block?
SAN depolarises as normal, but fails to rad atria
ECG appearance Sinoatrial block
P wave fails to appeare in expected place
Hence no QRS
Subsequent P waves in norm place
2nd degree heart block
Excitation intermittently fails to pass through AVN/bundle of his
What are the 3 types of 2nd degree heart block
Mobitz II
Wenckebach/Mobitz I
2:1/3:1
Mobitz II phenomenon
Constant PR interval
Sometimes = atrial contraction w/ no ventric contraction
Most P followed by QRS
Occasionally, P not followed by QRS
Wenckebach phenomenon
Progressive PR lengthening until atrial beat is not conudcted - no QRS
Then cycle repeats
2:1 or 3:1 conduction
2x or 3x as many waves as QRS complexes
What is complete/3rd degree heart block
Atrial contraction normal
No beats conducted to ventricles
Complete heart block - ECG appearance
P waves dissoc from QRS
Wide QRS - escape rhytm
What is AV dissociation
If escape rhythm from AV junction or ventricles occurs during sinus brady C
AV dissociation ECG appearance
QRS slightly higher than P wave rate
