This document provides information on interpreting EKGs, including: 1. It outlines the 6 main steps to interpret an EKG: identify P waves, measure PR interval, measure QRS complex, identify rhythm, determine heart rate, and interpret strip. 2. It describes common EKG components like the P wave, QRS complex, T wave, and explains how to measure intervals like PR and heart rate. 3. It discusses various arrhythmias and conduction abnormalities like heart blocks, junctional rhythms, atrial fibrillation, and provides characteristics to identify them on an EKG.

1. 6 - steps method EKG interpretation
1. Identify + examine the P waves
2. Measure the PR interval
3. Measure the QRS complex
4. Identify the rhythm
5. Determine the heart rate
6. Interpret strip
P wave =atrial depolarization
= 2 atriums Contract
QRS complex =ventricular
depolarization
= 2 ventricles Contract
T wave =ventricular repolarization
= 2 ventricles relax
!! Atrial repolarziation( relaxation )
occur after the P wave and could
be found in the QRS complex
amiodarone, hypocalcemia) increase the QT

2. P wave = should be present and upright
Inverted = junctional rhythm
Absent = ventricular
fi
brillation
PR interval = distance between P wave and the beginning of QRS
complex . What we do ??
We count the number of small boxes in between and multiply it by
0.04 seconds
!! Normal PR should be 0.12-0.20
> 0.20 = heart blocks
QRS complex: measure the small boxes in between the QRS
!! Normal = 0.08-0.12
>0.12 = PVC “ Premature ventricular contractions”
To identify the rhythm: measure the distance between R …R
Distance should be the same otherwise they will be
Irregular.
Heart rate :
1) 6 second method
Only If there are these lines then this is EKG is a 6 second strip
From the
fi
rst line to the third = 6 second strip
So we do 6 second method : we count the number of R between
these 3 lines and multiply by 10
Example this
fi
gure above: we have 6 R … 6*10= 60 Heart beat/min
!! Left atrial (LA) abnormality may cause broad, often
notched P waves in the limb leads and a biphasic P
wave in lead V1

3. INFO:
ABG “arterial blood gases”
= measurements of acidity and alkalinity of the arterial
circulation+ measure gases( ex: oxygen + carbon dioxide)
4 main components of ABG = PH + CO2+ HCO3
“bicarbonate” + PaO2”oxygen”
Heart blocks
May be found between SA node and the AV node or between
the AV node and the bundle of his to the purkinjie
fi
bers .
Causes : scarring of cardiac cells due to aging , heart attacks
, valve infections by endocarditis / medications “ex: digoxin”.
4 Types :
1. First degree heart block : partial block between the sa
node and the av node .
EKG: consistent prolonged PR interval ( measure the small
boxes of PRI and multiply by 0,04)
2) big box method
Divide 300 by the number of big boxes between 2 R
300/5 =60 BPM

4. 2. second degree heart block type 1”wenckebach”
Progressive block between av and sa node
ECG: begin with normal PRI then Progressive longer PRI
then dropped QRS .
!! Longer PRI is because of the delay from the conduction
from sa node to purkinje
fi
bers
3. second degree heart block type 2 / mobitz II
Intermittent block between sa and av node , block is complete
not partial.
ECG: drop in
QRS complex
+constant PR
interval
4. third degree heart block
” Complete heart block “+ bradycardic rhythm
ECG: no correlation between P waves and QRS complex
P waves have the same distance also QRS has same distance ,
but there is no correlation … p waves occur because atriums are
contracting ….and QRS occur because ventricles are
contracting, but they are independent .

5. Junctional Rhythms
Here the SA node fails / it has weak impulse…. Then the AV node will take
place and generate it’s own impulse…. That makes the typical junctional
heart rhythm= 40-60/min.
Characteristics :
1. HR 40-60 bpm
2. P wave is inverted / absent … also there may be a “ retrograde
impulse” where the inverted P wave goes after the QRS complex
Classi
fi
cation :
Junctional rhythm 40-60 bpm
Accelerated Junctional rhythm 60-100 bpm
Junctional tachycardia >100 bpm
Junctional Bradycardia < 40 bpm
!! The only thing that di
ff
erentiate between them is the heart rate ,,,, and
has one thing in common which is that the P wave is inverted /absent .
! Other Classi
fi
cation
Premature junctional complex (PJC)
Wandering junctional pacemaker dysrhthmyia
P wave -retrograde

6. Atrial
fi
brillation + Atrial Flutter
In atrial
fi
brillation:
Instead of having just the SA node conducting the
fi
rst
impulse toward the AV node … we will have several
cardiac cells in atriums ,,, they conduct their own impulse
with the SA node causing both atriums to contract much
faster than normal .
Characteristics :
1.“Regularly irregular rhythm “= distance between R
intervals will be di
ff
erent
2. No de
fi
nite P-waves
We call these in circles “ quiver waves
Types
Determined by the HR …
if 60-100 bpm = controlled atrial
fi
brillation
If < 60 bpm = atrial
fi
brillation with slow ventricular
response
If 101-150 = atrial
fi
brillation with rapid ventricular
response
If > 150 bpm = uncontrolled atrial
fi
brillation
In Atrial
fl
utter :
There is only one extra cardiac cell on top of SA node
either in left or right atrium.
-Saw-tooth waves
-Regular rhythm

7. Chest Leads
v1-v6”
precordial
leads”
The chest leads look at the heart in a horizontal
plane
V1 the right most view and V6 the left most .
!! In normal conduction, depolarization of the septum
starts from the left bundle going to the right toward v1
away from v6 , the left ventricle is larger so
the movement is to the left away from v1 to
v6 .
This causes negative wave in V 1 and
positive wave in v6.
—From v3-v4 it is isoelectric with
similar pos + neg de
fl
ections ..known as
transitional zone .
If transition happens in V2 = early transition/
rightward shift / counterclockwise
rotation .
2
ty
pes of leads
1) six chest leads v1-v6 ( examine the
fl
ow of depolarization
and repolarization of the heart in horizontal plane )
2) frontal leads ( examine the electrical events in verticalplane)

8. If it happened after V4 = late transition /
leftward shift / clockwise rotation
Causes may be : incorrect placement of
electrodes ( too low /high) / Anatomical
variations
— increase in R wave from V1-V5 known as
R wave progression
!! clockwise rotation more likely pathological
Example : COPD , anterior myocardial infarction ,
dilated cardiomyopathy
!! counterclockwise rotation more common in healthy
individual
Clinical causes ex: condition problems “ posterior MI”
Electrical shift to the right “RVH”
!! If transitional zone is absent / unclear = pathological
In this case we look at the R wave progression ,,, non/
poor progression …R wave stay low and S wave
remains deep in all chest leads = extensive anterior MI
— reverse progression of R wave ,,tall Wave in V1 /v2=
seen in right ventricular hypertrophy ( because
increased muscle mass in the right ventricle result in
net electrical movement toward the right chest leads.

9. Frontal leads
2 groups : standard limb ( I II III ) + augmented
vector ( aVR aVL aVF )

10. !!! These groups of leads do not only analyze
cardiac electrical events in the anatomical area
indicated
lead V1 : fourth intercostal space to the right of the sternum
lead V2: fourth intercostal space, just to the left of thesternum
lead V3 : midway between V2 and V4; lead V4, midclavicular line,
fi
fth intercostal
space
lead V5 : anterior axillary line, same level as V4
lead V6 :midaxillary line, same level as V4 and V5. A

11. Myocardial infarction
ECG (during / following MI ) :
1.Pathological Q waves
2.New QRS axis deviation
3.Poor R wave progression
4.Conduction block “AV block, bundle
branch block )