eLFH - The Electrocardiogram Part 3 Flashcards
ECG features of AF
Narrow complex tachyarrhythmia
Absence of P waves
Irregularly irregular ventricular response
Common causes of AF
Electrolyte disturbance - especially low K+ or low Mg2+
Dehydration
Valvular (especially mitral) disease
IHD
HTN
Hyperthyroidism
Main considerations of AF patients
Consider anticoagulation - risk of thromboembolic events
Rate control - tachycardia may provoke heart failure
ECG features of Atrial Flutter
Narrow complex tachyarrhythmia
Saw tooth baseline at rate of 300 bpm
Variable conduction to ventricles - 2:1 = 150 bpm, 3:1 = 100 bpm
Drugs to avoid in WPW with SVT
Drugs that slow AV conduction - e.g. Digoxin
Otherwise leads to direct transmission of atrial rate to ventricles via accessory pathway and results in VT
Differentials for broad complex tachycardia
Monomorphic ventricular tachycardia
Polymorphic ventricular tachycardia (Torsades de Pointes)
Ventricular fibrillation
SVT with aberrant conduction (i.e. bundle branch block)
Features which may differentiate VT from SVT with aberrant conduction
VT more likely if presence of:
- P waves
- Capture beats
- Fusion beats
Above features indicate there is independent atrial and ventricular activity occurring
ECG example of P waves in VT
Capture beat definition
Independent atrial depolarisation occasionally reaches AV node at appropriate time to ‘capture’ cardiac conduction to produce narrow QRS complex within the VT rhythm
Fusion beat definition
Similar to capture beat - atrial depolarisation timed such that it arrives simultaneously with ventricular depolarisation
QRS morphology is part way between broad VT complex and narrow complex
Left atrial hypertrophy causes
Aka P mitrale
Mitral valve disease
LAH can predispose to AF
Left atrial hypertrophy ECG changes
Increased P wave amplitude > 2.5 mm and duration > 0.12 s
Notched P wave (looks like an M shape - M for P Mitrale)
Right atrial hypertrophy causes
Aka P pulmonale
Seen in chronic lung disease tricuspid valve disease
Right atrial hypertrophy ECG changes
Only increased P wave amplitude > 2.5 mm
Duration of P wave not prolonged
Best seen in II, III, aVF
Left ventricular hypertrophy causes
Hypertensive disease
AS
HOCM
Left ventricular ECG changes
Various criteria can be used - most common is:
S wave in V1 + R wave in V5 or V6 (whichever is largest) >=35 mm
LVH can also be associated with LV strain (ST depression)
Cause of strain pattern in LVH
Likely due to more severe hypertrophic disease
Increased muscle mass causes higher LV diastolic pressures when coronary perfusion occurs - results in less coronary perfusion and myocardial ischaemia
Right ventricular hypertrophy causes
RV overload
E.g. Pulmonary hypertension
Right ventricular hypertrophy ECG changes
Dominant R wave in V1
Right axis deviation
Coronary blood supply
ECG territories associated with Anterior-septal ischaemia and Coronary artery associated
V1-V3
Left anterior descending artery
ECG territories associated with Anterior-lateral ischaemia and Coronary artery associated
V1-V6
Left main stem
ECG territories associated with High lateral ischaemia and Coronary artery associated
I and aVL
Circumflex
ECG territories associated with inferior ischaemia and Coronary artery associated
II, III and aVF
Right coronary artery
Most likely to be associated with atrioventricular heart blocks
ECG territories associated with posterior ischaemia and Coronary artery associated
V1 and V2 - inverse of usual changes (ST depression, R wave rather than Q wave)
Right coronary artery or circumflex depending on which system is dominant
May be associated with inferior or lateral infarct depending on affected artery
ECG territories associated with Subendocardial ischaemia
Any leads
ECG changes with coronary ischaemia seen within first hours
ST elevation
ECG changes with coronary ischaemia seen in days
Abnormal Q waves appear
T wave inversion may be seen
ECG changes with coronary ischaemia seen in weeks
ST segments resolve to normal
Q waves remain present
ECG changes with high Mg2+
Prolonged PR
Wide QRS
ECG changes with low Mg2+
Prolonged PR
ST depression
Flat T waves or Peaked T waves
Wide QRS
Long QT
U waves
ECG changes with high Ca2+
Short QT
ECG changes with low Ca2+
Long QT
ECG changes with high K+
Tall tented T waves
Wide QRS
Prolonged PR
Flattened P waves
VT / VF / Asystole
ECG changes with low K+
Prolonged PR
ST depression
Flattened or inverted T waves
U waves
VF / ventricular ectopics
