ECG and Arrhythmias Flashcards
Measuring Axis
If QRS complexes are leaving each other between lead I and aVF = Left Axis Deviation
If QRS complexes are reaching = R axis deviation
Limb Electrode placement
RA: Red
LA: Yellow
LL: Green
RL: Black
Leads for parts of the heart
Lateral
Inferior
Septum
Anterior
Posterior
And which coronary vessel supplies that area
Lateral: I, aVL, V5, V6 - Lcx or LAD
Inferior: II, III and aVF - RCA or Left circumflex
Septum: V1 V2 - LAD
Anterior: V3 V4 - LAD
Posterior: Invert / flip the egg over looking at V1 - V3 (or stick more electrons to the back)
ECG wave form and what they represent
P wave and pathology (2)
PR interval (2)
P wave represents atrial depolarisation:
- P pulmonale - tall P wave due to right atrium hypertrophy
- P mitrale - bifid p wave due to left atrium hypertrophy
PR interval - reflects time taken to depolarise atria and conduction through the AV node:
<120 ms = accessory pathway (+delta wave in Wolff Parkinson white syndrome)
>120ms = AV heart block
QRS complex
Pathological Q waves
What should R waves do
How to look at QRS
Electrical Alternans
ST segment
T wave
QRS represents ventricular depolarisation
Pathological Q waves is if they are more than 25% of R wave and represents full thickness myocardium ischaemia
R waves should progressively get larger from V1 to 6
S wave (negative deflection after R wave)
Looking at QRS:
- Width: narrow <100ms, broad >120ms. Broad due to pacemaker, BBB etc.
- Voltage: height
- Morphology e.g. delta wave in WPW due to ventricles being stimulated faster due to accessory pathway
Electrical alternans - QRS waves alternate in height => pericardial effusion -> cardiac tamponade
ST segment should be isoelectric and measured from J point
ST elevation all over is pericarditis. In specific areas -> MI
T wave represents ventricular repolarisation - Tented in hyperkalaemia
QT interval
QTc
What can prolonged QTc result in? How do you treat?
U wave
Q wave to end of T wave 9time for ventricular de and depolarisation)
Prolonged QTc: - low electrolytes (K+, Mg2+ etc.)
- antipsychotics
Prolonged QTc can go into torsades (polymorphic VT) - treat with magnesium sulphate
Short QTc: hypercalcaemia
U wave - hypokalaemia
Calculating RATE
Rate - 300 / no. large squares between R waves
Rhythm
Regular?
Are there p waves?
Normal looking p waves? e.g. sawtooth in atrial flutter
P wave positive in lead II and negative in aVR = sinus rhythm
Each p wave followed by QRS in 1:1 relationship?
Bradyarrhythmias
Types
Mx
AV block
1st degree: not really clinically significant. Fixed prolonged PR interval
2nd degree: dropped beats/ QRS complex
Type 1 - PR prolongs until dropped beat
Type 2 - fixed PR interval with dropped beat occurring at a fixed interval e.g. 2:1
3rd degree: no connection between P wave and QRS
Complete Mx: Atropine and hold rate limiting drugs
Tachyarrhythmias
Regular:
- Narrow QRS: SVT (inc. AVRT, AVNRT - most common etc.)
- Broad QRS: VT
Irregular: Atrial fibrillation
Indications for DCCV cardioversion
4 adverse signs:
- reduced consciousness (i.e. syncope)
- shock (systolic <90)
- Myocardial ischaemia
- heart failure
Management of SVT
Management:
1. Vagal manouveurs e.g. carotid sinus massage, vasalva manoeuvre
- Adenosine IV 6mg first then 12 mg then 12 mg
(can’t give in asthma bc bronchoconstriciton so give verapamil instead)
Ongoing: rate control - best blockers, calcium channel blockers
Be aware AV blocking drugs (beta blocker, calcium channel blocker, adenosine) are contraindicated in Wolf Parkinson White syndrome
so use Flecanide instead
Management of Atrial Fibrillation
Rate control:
Beta Blocker
Calcium Channel Blocker
Digoxin
Rhythm Control: Amiodarone, Flecanide
Anticoagulation
Treat Cause
Management of Heart Block
Cardiovert if have 4 signs
Atropine 500 micrograms (repeat until 3 mg)
Long-term management: pace maker
Atrial Flutter
2:1 to 4:1 conduction so HR 75 or 150 bpm
Sawtooth atrial activity pattern
