ECG Flashcards
How fast is standard ecg paper travelling?
25mm/s
What is a large ecg square equal to?
5mm
0.2s
What is a small ecg square equal to?
1mm
0.04s
Which leads measure the inferior surface of the heart?
II
III
aVF
Which leads measure the anterior surface of the heart?
V1
V2
V3
V4
Which leads measure the lateral surface of the heart?
I
aVL
V5
V6
Which leads measure the right atrium and LV cavity?
V1
aVR
How do you perform a 15-lead ECG?
V4 to the right 5th IC space MCL
V5 round backwards to the inferior tip of scapula
V6 to midway between V5 and spinal column.
What is the P wave showing?
Spread of electrical activation through atrial myocardium starting from SA node
Atrial depolarisation
What is the PR interval showing?
Time taken by atrial depolarisation
Conduction of impulse through Av node
What is the QRS complex showing?
Ventricular depolarisation
What is the ST segment showing?
Pause in ventricular electrical activity before repolarisation
What is the T wave showing?
Ventricular repolarisation
What is the U wave showing?
Uncertain
Possible due to after potentials at beginning of systole
Repolarisation of the mid-myocardial cells, that is, those between the endocardium and the epicardium and the His-Purkinje system
What is the cause of a U wave?
Hypokalemia
Hypercalcemia
Can be normal (athletes)
What is a sinus rhythm on ecg?
Regular p waves followed by QRS complex
What is the difference between atrial fibrillation and atrial flutter?
Atrial fib = irregular ventricular rate
Atrial flutter = regular ventricular rate
How do you calculate ventricular rate?
Count number of large squares from R to R
Divide by 300
How do you calculate atrial rate?
Count number of large squares from P to P
Divide by 300
What is a left axis?
QRS + in I
- in aVF
What is a right axis?
QRS - in I
+ in aVF
What is a normal axis?
QRS + in I and + in aVF
What is an extreme right axis?
QRS - in I and - in aVF
Give causes of left axis deviation
Systemic hypertension
IHD
AMI
Increased LV
Give causes of right axis deviation
COPD
Increased RV
Pulmonary hypertension
Pulmonary embolism
What does a tall peaked P wave in leads II, III and aVF show?
Right atrium hypertrophy