Basics
EKG paper→
-Small squares of 1 X 1 mm, large squares of 5 X 5 mm
-Horizontal axis (time): one small square = 0.04 secs, large square = 0.2 secs
-Vertical axis (voltage): one small square = 0.1 mV, large square = 0.5 mV
Leads→
-Six limb leads (3 standard, 3 augmented) for frontal plane
*Inferior leads: II (+60), III (+120) , and AVF (+90)
*Left lateral leads: I (+0), AVL (-30)
*AVR (-150)
-Six precordial leads for horizontal plane
*V1 – V4 anterior leads, V5 – V6 left lateral leads
*V1 (smallest)-V5 (largest) see R wave progression
*V3 to V4 see transition zone, where QRS complex goes from being predominantly negative too predominantly positive
-Anterior (V1, V2, V3, V4), lateral (I, AVL, V5, V6), inferior (II, III, AVF), AVR
Normal times/values
P wave < 0.12 secs and < 2.5mm
PR interval (beg of atrial depolar→beg of ventricular depolar) 0.12-0.2 secs
QRS interval (start to end of ventricular depolarization) 0.06 – 0.1 secs
P Wave
Small, usually positive in left lateral and inferior leads
Often biphasic in leads III, and V1
Most positive in lead II, most negative in lead AVR
Beginning of P wave = RA component; end of P wave = LA component
Axis (Leads I and AVF)
Normal axis (between 0 and +90) , pos. lead 1, pos. lead AVF
Right axis deviation (between +90 and +180) neg. lead 1, pos. lead AVF
Left axis deviation (between 0 and -90) pos. lead 1, neg. lead AVF
Extreme right axis (between +90 and +180) neg. lead 1, neg. lead AVF
*find lead where QRS complex biphasic, then either subtract or add 90deg to determine the axis precisely
Atrial enlargement
*look at lead II because nearly parallel to atria current flow (most + )
*look at lead V1 because nearly perpendicular, therefore biphasic QRS
RA enlargement (P pulmonale)
1) P wave amplitude > 2.5mm in inferior leads
2) No change in P wave duration
3) Possible R axis deviation
LA enlargement (P mitrale)
1) Terminal (negative) component of P wave amplitude > 1mm below isoelectric line in lead V1
2) Increase in P wave duration, with terminal (negative) portion > 0.04 secs, or 1 small block
3) No significant axis deviation
Ventricular hypertrophy
RVH
1) Right axis deviation, with QRS axis > +100
2) R wave > S wave in V1, S wave > R wave in V6
LVH (based on voltage criteria, may see secondary repolarization abnormalities)
Precordial leads (criteria does not apply in pts < 35yo)
1) R wave in V5 or V6 plus S wave in V1 or V2 > 35mm
2) R wave in V5 > 26mm
3) R wave in V6 > 18mm
4) R wave in V6 > R wave in V5
Limb leads
1) R wave in AVL > 13mm
2) R wave in AVF > 21mm
3) R wave in lead I > 14mm
4) R wave in lead I plus S wave in lead II > 25mm
*Left axis deviation > -15
**Secondary repolarization abnormalities include asymmetric T wave inversion and down-sloping ST segment depression
September 16th 2010