ECGs Flashcards
What does myocardial damage present as in an ECG?
A raised ST segment
What leads represent the Lateral leads (left lateral wall)?
I, aVL, V5 and V6
What leads represent the Inferior leads?
II, III and aVF
What leads represent the Anterior leads?
V3 and V4
What leads represent the Septal leads?
V1 and V2
What axis does lead I compare?
aVR - aVL
What axis does lead II compare?
aVR - aVF
What axis does lead III compare?
aVL - aVF
What is the major conduction pathway in the heart?
SA - AV - His - BB’s - Purkinje
Why is lead II best to monitor?
Hearts depolarisation is in the same axis as the lead
What mechanically does a p wave represent?
Atrial contraction
What mechanically does the QRS complesx represent?
Ventricular contraction
What mechanically does the T wave represent?
Relaxation of the myocardium
How much time does one large box represent?
0.2 seconds
How much time does one small box represent?
0.04 seconds
What does the P-R interval represent?
The timescale of atrial activity
atrial depolarisation
What does the QRS complex represent?
Time taken for full ventricular myocardium depolarisation
What does the Q - T interval represent?
Total duration of ventricular activity (depolarisation and repolarisation)
What lead is always negative in a normal ECG?
aVR
What can ‘pathological q waves’ represent?
LBBB
aMI (late sign)
Scar tissue
Conduction issues
What can an increased PR interval represent?
AV node blocks
What can a decreased PR interval represent?
Wolff-Parkinson-White
What can a prolonged QT interval lead to?
Torsades de Pointes
What can pronlonged QRS intervals be a sign of?
Bundle Branch Blocks
PVC
Venricular Rhythms
What does ST depression likely indicate?
Ischaemia (narrowing for a coronary artery)
What does ST elevation likely indicate?
Necrosis of the myocardium
MI
What occurs in sinus arrhythmia?
Sinus with a variable rate
HR increases with inspiration and decreases with expiration
What causes sinus arrhytmia?
SA node pacemaker activity varies reflexively with respiration
What is ‘p pulmonale’ and what does it indicate?
Tall peaked p wave indicating R atrium enlargement
What is ‘p mitrale’ and what does it indiicate?
Broad notched p wave
indicating LA enlargement (mitral valve disease)
Why does atrial fibrilliation occur?
Atrial depolarisation is disorganised leading to a chaotic ventricular rhythm
What are some causes of AF?
Hypertension IHD Alcohol Mitral valve disease Myocarditis
What ECG pattern is usually seen in atrial flutter?
Sawtooth pattern
What 4 characteristics are generally seen in a pericarditic ECG?
- Widespread ST elevation
- ST elevation concave upward
- T wave inversion
- Lack of Q waves
What is an atrial ectopic?
A premature discharge of an abnormal focus in either atrium
What will an atrial ectopic look like on an ECG?
Earlier than expected
Abnormal confirmation
When do junctional rhythms occur?
When electrical signal origionates further down the conduction system (near but not the AV node)
