ECG Flashcards
What is P?
atrial depolarisation
How long does P usually last?
0.08-0.10seconds
What is the QRS complex?
ventricular depolarisation
How long does the QRS complex usually last?
less than 0.10 seconds
What is T?
ventricular repolarisation
What occurs in the PR interval?
largely AV nodal delay
How long is the PR interval usually?
0.12-0.2 seconds
What occurs in the ST segment?
ventricular contraction
What occurs in the TP interval?
ventricular relaxation
What is the ECG paper speed?
25mm/second
How do you calculate the heart rate if it is regular?
300 divided by the number of large squares between two beats (R-R interval)
How do you calculate the heart rate if it is irregular?
number of QRS complexes in 30 large squares multiplied by 10
How many seconds does one large box stand for?
0.2
How many seconds does one small box stand for?
0.04
Where do the limb electrodes go?
RA, LA, LL and RL (neutral)
What are the 6 limb leads?
I, II, III, aVF, aVL, aVR
Why is aVR inverted?
the predominant vector is depolarisation moving away from the electrode
Why are the P and T waves poorly resolved in limb lead III?
the predominant vector is approx. perpendicular to the lead axis
The predominant vector is approx. parallel to lead axis in limb lead II. What does this result in?
well resolved P and T waves
What is a lead?
imagine a line between two electrodes
Where is the neutral, reference electrode?
RL
Where is V1?
right sternal edge, 4th intercostal space
Where is V2?
left sternal edge, 4th intercostal space
Where is V3?
half way between V2 and V4
Where is V4?
5th intercostal space, midclavicular line
Where is V5?
anterior axillary line
Where is V6?
mid axillary line
What does broad complex tachycardia show?
A ventricular problem
What do narrow QRS complexes show?
Atrial origin
What do broad QRS complexes with slurred upstroke on the R/delta wave show?
Wolff-Parkinson-White syndrome
What does an absent P wave show?
sinoatrial block
Bifid P wave?
LA hypertrophy e.g. in mitral stenosis
Peaked P wave?
RA hypertrophy e.g. pulmonary HT, tricuspid stenosis
ST depression?
myocardial ischaemia
ST elevation?
Acute MI
‘Saddle’ shaped ST elevation?
acute constrictive pericarditis
Irregularly irregular rhythm?
AF
Sawtooth rhythm strip?
atrial flutter
long PR interval?
1st degree heart block
Describe Mobitz type I on an ECG.
PR interval gradually decreasing from cycle to cycle until the AV node completely fails and a QRS complex is missing
PR interval is constant, but every nth QRS is missing?
Mobitz type II
W pattern in V1, M pattern in V6?
LBBB
M pattern in V1, W pattern in V5?
RBBB
dissociation between P waves and QRS complexes?
complete heart block
What are the lateral ECG leads? e.g. for describing an MI
I, aVL, V5-6
What are the septal ECG leads?
V1-2
What are the inferior ECG leads?
II, III, aVF
What are the anterior ECG leads?
V3-4
