ECG Tips
21/2/11
FANZCA Notes
Life in the Fast Lane
Crit-IQ
PY Mindmaps
Stuart Lane Tutorial – Nepean Written Course (2011)
The 12 Lead ECG
- 10 physical leads
- 12 electrical leads
CALIBRATION
-
normal = 25mm/s
calibration = 5mm wide, 10mm high = 1mV
1 small square = 1mm = 0.04s = 40ms
1 large square = 5mm = 0.2s = 200ms
RATE
- QRS complexes on rhythm strip x 6 = rate/min
- number of large squares between R waves: 300-150-100-75-60-50
Tachycardia
- narrow complex vs wide complex?
- narrow:
Jeremy Fernando (2011)
-> AV node independent (ST, unifocal, mutlifocal, AF, Aflu)
-> AV node dependent (AVN re-entry, AV re-entry, junctional)
- wide:
->
->
->
->
VF
supra-ventricular tachycardia with BBB
VT
accelerated idioventricular rhythm
- regular or irregular?
- irregular:
-> multiple ventricular ectopics
-> AF with aberrancy
-> AF with BBB
-> AF with pre-excitation pathway
- regular:
-> sinus
-> junctional
Bradycardia
- sinus:
->
->
->
->
->
arrest
pauses
inappropriate bradycardia (vagal overactivity, myxoedema)
physical fitness
beta blockade
- AV node dysfunction:
-> 1st degree – prolongation of PR interval (>0.2s)
-> 2nd degree (Mobitz type I) – progressive lengthening of PR interval with eventual
dropped ventricular conduction
-> 2nd degree (Mobitz type II) – intermittent dropping of ventricular conduction
-> 2nd degree (2:1 type) – alternate p-wave not conducted to ventricles
-> 3rd degree – complete dissociation between atria and ventricular
RHYTHM
- SR or not?
AXIS
-
QRS positive in I and aVL = normal
I positive and aVF negative = LAD
I negative and aVF positive = RAD
I and aVF negative = extreme RAD or LAD
RAD
Jeremy Fernando (2011)
-
RVH
Left posterior hemiblock
Lateral myocardial infarction
Acute right heart strain (PE)
Normal in infants and children
LAD
-
AS
Dilated cardiomyopathy
AMI
IHD
HT -> aortic root dilation -> AR
Left anterior hemiblock
Extreme Axis Deviation
- situs inversus
- limb lead on backwards
- VT
P WAVE
= atrial depolarisation
-
look for in V1 and II (best seen)
must be negative in aVR (otherwise leads misplaced)
normal duration: 0.12s
normal eight: < 2mm
-
dual: heart transplant
bifid: LA enlargement (mitral stenosis)
peaked: RA enlargement (pulmonary hypertension) or LA enlargement
inversion: atrial ectopic, junctional rhythms, dextrocardia
variable morphology: multifocal atrial rhythms
PR INTERVAL AND PR SEGMENT
-
normal duration 0.12-0.2s (3 to 5mm)
long: 1st, 2nd (type I and II) and 3rd degree HB
short: WPW, LGL
depression: pericarditis, atrial ischaemia
Q WAVES
- normal: < 25% of R wave in I, aVL, aVF, V4,5,6.
- pathological: if long (>0.04s) and deep (>2mm)
QRS COMPLEX
- normal duration < 0.12s (3 small squares)
- normal transition point of R wave: V3-V4
Jeremy Fernando (2011)
- amplitude: normal, large, low voltage, alternans
- morphology: notched, RBBB, LBBB
Positive QRS in V1
- RVH
- posterior infarction
- WPW type 1
- RBBB
- Duchenne’s muscular dystrophy
- dextrocardia
- incorrect lead placement
- rare causes: LV ectopics, acute right heart strain, hypertrophic cardiomyopathy, normal
variant, Brugada syndrome
J WAVE
= positive deflection @ QRS and ST junction (J point)
1. Hypothermia (increases with severity)
2. Severe hypercalcaemia
ST SEGMENT
ST Elevation
1.
2.
3.
4.
5.
6.
7.
AMI
Pericarditis (with PR interval depression)
Tako-tsuba cardiomyopathy
LBBB
Brugada syndrome
Benign early repolarisation (isn’t so benign -> higher risk of cardiac death)
LV aneurysm
Contour
- horizontal
- upsloping
- downsloping
T WAVE
-
normal amplitude: < 2/3rds R wave
peaked
inverted
alternans
U WAVE
= small positive deflection following T wave
1. Hypokalaemic Periodic Paralysis
Jeremy Fernando (2011)
2. Bradycardia
3. Hypothermia
4. Drug OD – digoxin, phenothiazines, anti-arrhythmics (sotalol, amiodarone, quinidine,
procainamide)
5. Hypomagnaesaemia
6. Hypocalcaemia
7. Increased ICP
QT INTERVAL
-
rate dependent
should be less than 50% of R-R interval
measure in II or V5-6 (include large u wave that is fused with T wave)
QTc > 440ms (11 small squares) in men or > 460ms in women (11.5 small squares)
Causes of Prolonged QT
-
drugs: anti-arrhythmics, anti-histamines, macrolide, anti-depressants, methadone…)
electrolytes: hypokalaemia, hypoMg2+, hypocalcaemia
stroke: SAH
ACS
bradyarrhythmia
congenital
-> complication = Torsade de Ponte
OTHER CONDUCTION DISTURBANCES
RBBB
-
activation of the right ventricle is delayed
QRS > 120ms
RSR in V1 (‘M’), and ‘W’ in V6 (MARROW)
broad S wave in LV leads (I and V6)
normal axis
1.
2.
3.
4.
5.
Can be normal
Massive PE
RVH
IHD
Congenital heart disease
LBBB
-
septal depolarisation reversed (right to left) -> change in initial direction of QRS
QRS > 120ms
Q waves seen in left ventricular leads
WILLIAM (W in V1, M in V6)
normal axis
always pathological
1. IHD
2. Cardiomyopathy
3. LVH
Jeremy Fernando (2011)
Left anterior hemiblock – LAD, Q waves in I and aVL, small R in III (and absence of LVH)
Left posterior hemiblock – RAD, small R in I, small Q in III (and absence of RVH)
Bifascicular block
- RBBB + block of either left anterior or posterior fascicle.
- RBBB + left anterior fascicle block -> LAD
- RBBB + left posterior fascicle block -> RAD
Trifascicular block – 8 types:
(1)
(2)
(3)
(4)
(5)
(6)
(7)
(8)
Prolonged PR interval + LAD + RBBB
LBBB + RAD
AF + LAD + RBBB
Junctional rhythm + RAD + RBBB
Alternating BBB
RBBB + alternating fascicular block
BBB + second degree HB type II
Any bifascicular block + 1st or 2nd degree AV block
TRICKS AND TRAPS
Artifacts – tremor
Dextrocardia
- RAD
- P in I
- QRS complexes decrease in amplitude across the chest leads
HypoMg2+
-
wide QRS
peak T waves
R prolongation
TWI
U waves
VT -> Torsades
Lown-Ganong-Levine
- short PR interval < 0.12s
- no delta wave
- may have normal QRS (unless IVCD present)
Overdose -> Na+ channel blockade
1. Positive QRS in II
2. Dominant R wave in aVR
3. QRS duration > 100ms
Packing Spikes – failure to sense/capture/output
Jeremy Fernando (2011)
WPW
- PR interval < 0.12s
- QRS duration > 0.12s
- Delta wave
Cardiac Arrest in a Young Person
-
ARVD: RV strain and epsilom wave
Long QT: TW after 50% of R-R distance
Brugada: V1 and V2 have funny ST elevation
HOCM: LVH
WPW: see above
V5R – most sensitive lead for RV infarction (ST segment will be elevated)
Pericardial tamponade
- electrical alternans -> heart swinging in massive pericardial effusion (c/o change in
impedance)
ELECTROLYTE ECG CHANGES
Hyperkalaemia
-
tall T waves
flat P waves
prolonged PR
wide QRS
Hypokalaemia
-
ST depression
T wave flattening
U waves
SVT
VT
Torsades de Pointes
Hypermagnasaemia
- bradyarrhythmias
- cardiac arrest
Hypomagnasaemia
-
prolonged PR
wide QRS
ventricular arrhythmias
Torsades
Jeremy Fernando (2011)
Hypercalcaemia
- shortened QTc
- Osborn or J wave
Hypocalcaemia
- prolongation of ST segment and QT interval
- VT
Jeremy Fernando (2011)