how to read 12 lead ecg

How to read ECGPG corner

Mr do not Miss

Lead reversal and ECG artefacts

Technology does not understood science of ECG

Do not believe in COMPUTERIZED ECG INTERPRETATIONS

At least 14 observationsbefore answering

Standardization

Usual 1 mV = 10 mm In special cases ECG may be intentionally recorded at

one-half standardization (1 mV =5mm) or two times normal standardization (1 mV = 20 mm). However, overlooking this change in gain may lead to the mistaken diagnosis of low or high voltage.

Rhythm

Sinus rhythm bradycardia or tachycardia SR with APBs or VPBs SR with AV block

Nonsinus:PSVT), Afib or flutter, VT and AV junctional escape

Sinus rhythm

Discrete P waves that are always positive (upright) in lead II (and negative in aVR

Heart Rate

Normally, the ventricular (QRS) rate and atrial (P) rates are the same (1:1 AV conduction)

Tachycardia >100

Bradycardia <60

Irregular Regularly irregular :Wenchebach’s Irregularly irregular :Fib

PR Interval

The normal PR interval (measured from the beginning of the P wave to the beginning of the QRS complex) is 0.12 to 0.2 sec

First-degree AV block

A short PR interval with sinus rhythm and with a wide QRS complex and a delta wave is seen in the Wolff-Parkinson-White (WPW) pattern

A short PR interval with retrograde P waves (negative in lead II) generally indicates an ectopic (atrial or AV junctional) pacemaker.

P wave

Normal not exceed 2.5 mm in amplitude and is less than 3 mm (120 ms) wide in all leads

Tall, peaked P waves may be a sign of right atrial overload (P pulmonale)

Wide (and sometimes notched P) waves are seen with left atrial abnormality.

QRS Interval

0.1 sec (100 ms) or less, measured by eye

110 ms if measured by computer

QT/QTc Interval

Shortened :hyperkalaemia and digitalis effect

Prolonged:hypocalcemia or hypokalemia, drug effects (quinidine, procainamide, amiodarone, or sotalol), or myocardial ischemia

QRS Voltage

Stick to criteria for Normal /LVH/RVH

QRS Axis Frontal plane

Normal: −30° to +100°

R wave progression

Inspect leads V1 to V6

Normal increase in R/S ratio occurs as you move across the chest

Poor: (small or absent R waves in leads V1 to V3) AWMI

The term reversed R wave progression Tall R waves in lead V1 that progressively decrease in

amplitude:RVH, posterior (or posterolateral) infarction, and dextrocardia

Q,T,U Document changes

U Wave U Waves Look for prominent U waves. These waves,

usually most apparent in chest leads V2-V4, may be a sign of hypokalemia or drug effect or toxicity (e.g., ami-odarone ami-odarone, dofetilide, quinidine, or sotalol).

Normal frontal loop:1.q in II/III/aVF2.No q in I/AVL

Counter clock loop in frontal plane:1.q in AVL2.No q in II/III/AVF

(1) standardization—10 mm/mV; 25 mm/sec(2) rhythm—normal sinus (3) heart rate—75 beats/min (4) PR interval—0.16 sec (5) P waves—normal size (6) QRS width—0.08 sec (normal) (7) QT interval—0.4 sec (slightly prolonged for rate) (8) QRS voltage—normal(9) QRS axis—about 30° (biphasic QRS complex in lead II with positive QRS complex in lead I) (10) R wave progression:early precordial transition with relatively tall R wave in lead V2 (11) abnormal Q waves—leads II, III, and aVF (12) ST segments: elevated in leads II, III, aVF, V4, V5, and V6 slightly depressed in leads V1 and V2 (13) T waves—inverted in leads II, III, aVF, and V3 through V6 (14) U waves—not prominent. Impression: This ECG is consistent with an inferolateral (or infero-posterolateral) wall myocardial infarction of indeterminate age, possibly recent or evolving. Comment: The relatively tall R wave in lead V2 could reflect loss of lateral potentials or actual posterior wall involvement

EXAMPLE

Calcium and 12 Lead ECG

What ECG findings may be present in pulmonary embolus?

Sinus tachycardia (the most common ECG finding)

Right atrial enlargement (P pulmonale)—tall P waves in the inferior leads

Right axis deviation

T wave inversions in leads V1-V2

Incomplete right bundle branch block (IRBBB)

S1Q3T3 pattern—an S wave in lead I, a Q wave in lead III, and an inverted T wave in lead III. Although this is only occasionally seen with pulmonary embolus, it is quite suggestive that a pulmonary embolus has occurred.

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