ECG INTERPRETATIONPart 2

ECG INTERPRETATIONPart 2

Coronal plane (Limb Leads)1. Bipolar leads - l , l l , l l l2.Unipolar leads - aVL,Avr aVF

Transverse planeV1 — V6 (Chest Leads)

10 electrodes

LIMB LEADS

Augmented limb leads

How to READ??

Standardization

Calibrate to 10mm/mV Rate at 25mm/s

Rhythm

“Constant Ps & Rs interval”. Every QRS must be preceded by a

P wave.

Heart rate

Regular: 300/RRbig or 1500/RR

For irregular Rhythm: 15 cm scalenumber of R waves in a 6-second

(30 big square) X 10.

AXIS

Neonate & infant: 90-150 child: 60-120 elder: “>12 years” 30-90

Left leaves

Right reaches

ECG INTERPRETATION PART 2

WAVES INTERVALS CHAMBER HYPERTROPHY

Waves

Physiological waves:P-wave:Best seen in Lead II Normally 2-3 small squares (0.08-

0.12 sec) duration & height “Simple 2.5X2.5”.

Height A tall P wave

(over 2.5mm) can be called P pulmonale

Occurs due to right atrial hypertrophy

Length A P wave with a

length >0.08 seconds (2 small squares) and a bifid shape is called P mitrale

It is caused by left atrial hypertrophy

QRS-waves

Q - First downward R - first upward R’ - 2nd upward S - first downward after 1st

upward QS

QRS-waves

QRS-waves

Duration: <3 small squares ( 0.12 secs )

Amplitude: Variable <2.0 mV or 4 big sq

Q wave: <3 small squares depth in “right leads” V1 , v2

QRS

Progression:A. Right to left: From mainly S in

V1 to mainly R in V6B. Age: From RV dominance in

neonates to LV dominance after age of 3 years.

R wave Progression

QRS

Narrow QRS Broad QRS RSR’ LVH vs RVH Delta slurring

T wave Repolarization begins in the last area of

the heart to have been depolarized, and then travels backward, in a direction opposite that of the wave of depolarization

both an approaching wave of depolarization and a receding wave of repolarization generate a positive deflection on the EKG,

T-wave:

V6 T - always upright. ( If inverted indicate LVH )

The amplitude, of T wave is one third to two thirds that of the corresponding R wave

V1 it is inverted from age of 1 week up to puberty “16 years”; upright after birth & after puberty.

T wave

Tall T wave Flat (< 0.5 mm negative ) Inverted (> 0.5 mm negative )

Pathological waves

1. Delta-wave2. J-wave (Osborne wave)3. R’ -wave4. U-wave

???

Interval /segment

Interval / segment

Intervals

PR Interval Normally, 2-5 small squares

(average 0.08-0.2 sec)

Long PR >5 Short PR <2

Q-T Interval

The duration of the QT interval is proportionate to the heart rate.

Q-T IntervalCount the number of small squares, then multiply by 0.04 seconds, that the QT in seconds.

Bazett Formula.

QTc = QT/square root of RR“RR: are the small squares between 2 R waves”

Crude normal value: 0.35-0.45 at rate between 60-100

Short Q-T: Hypercalcemia

Long Q-T: 5 Hypos “Thermia, Thyroidism,

Calcemia, Magnisemia & Kalemia” 2 Syndromes: Romano–Ward & Jervell

and Lange–Nielson “+Deafness” Drugs: e.g. Tricyclic Antidepressant

S-T segment

Elevated ST segment: Pericarditis / MI

Depressed ST segment: Ischemia ( Angina ) Hypokalemia.

Chamber size

RAE vs LAE RVH vs LVH

Chamber size

Right Atrial Enlargement: Tall P- wave “P pulmonale” ( >3 small squares )Lead II & V2

Left Atrial Enlargement:

Wide P- wave “P mitrale” >3 small squares (> 0.12 sec)Lead II & V6

RVH vs LVH

R wave Progression

Right Ventricular Hypertrophy

In lead V1, the R wave is larger than the S wave.

In lead V6, the S wave is larger than the R wave

With Right axis deviation

Left Ventricular Hypertrophy

R wave in V5 + S wave in > 35 mm.

R in V5 is 26mm, S in V1 in 15mm. The sum is 41 mm

Bi-Ventricular Hypertrophy

Sum of RS in V3 & V4 > 60

ECG INTERPRETATION PART 3

Arrythmias Heart block Myocardial infarction

Acute myocardial infarction

Three stages:

1. T wave peaking followed by T wave inversion

2. ST segment elevation3. Appearance of new Q waves

3 stages

Pathologic Q wave

The Q wave must be greater than 0.04 seconds in duration.

The depth of the Q wave must be at least one third the height of the R wave in the same QRS complex.

Lead AVR should not be considered when assessing possible infarction.

T wave inversion --- not diagnostic ST segment elevation is a reliable sign Appearance of new Q waves indicates

irreversible myocardial cell death has occurred

Reciprocal Changes --- at lead distant from an infarct ( ST segment depression )

Inferior infarction- inferior leads Lateral infarction - the left lateral

leads Anterior infarction - Any of the

precordial leads (V1 through V6) Posterior infarction- reciprocal

changes in the anterior leads, especially V1.

Arrythmia

Sinus arrythmia