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ECG Interpretation for

Primary Care PhysicianAamir A. Cheema M.D.



Welcome

Pakistan

Society of FamilyPhysicians



ECG Grid



6 Steps

1. Rate

2. Rhythm

3. Axis

4. Intervals

5. Hypertrophy

6. Infarction/Ischemia



Rate

300-150-100-75-60-50

300-150-100-75-60-50



What if rate is <50/min or rhythm is

irregular ?

Count the number of R waves in a 6 second stripand multiply by 10.

For example, if there are 7 R waves in a 6 secondstrip, the heart rate is 70 (7x10=70).



Rhythm

1. Locate the P wave

If absent and rhythm is irregular, think of atrial

fibrillation.

If present- check rate: If <60, bradycardia. If >100,

tachycardia. In general, if narrow-complex tachycardia is present and

heart rate is

100-150, think of sinus tachycardia

150-250, think of SVT (supraventricular tachycardia)

250-350, think of atrial flutter

>350, think of atrial fibrillation



Rhythm

2. Establish the relationship between Pwave and QRS complex

If 1:1, it is normal

If more P waves than QRScomplexes, think of AV block

If more QRS complexes than Pwaves, think of accelerated junctional or ventricular rhythm



Rhythm

3. Analyze the QRS morphology

If normal duration (<120 msec),

think of supraventricular origin e.g.normal sinus rhythm or

supraventricular tachycardia

If wide (>120 msec), think of ventricular origin e.g. ventricular

tachycardia



Axis



Intervals

PR interval: <200 msec(one big box)

QRS complex:<100 msec(2½ small boxes)

ST segment: evaluatefor elevation or depression

below baselineQT segment: roughly lessthan half of R-R interval

At high or low heart rates, calculate corrected QT intervalQTc = QT interval ÷ square root of the RR interval (in sec)

The normal value for the QTc is <440 msec (2½ big boxes)



Hypertrophy

Left ventricular hypertrophy criteria

Sum of S wave in V1 and R wave inV5 or V6 3.5 mV (35 mm)

and/or

R wave in aVL 1.1 mV (11 mm)



Normal ECG



Infarction

Clinically significant ST segmentelevation is considered to be presentif it is greater than 1 mm (0.1 mV) in

at least two contiguous precordialleads or in at least two adjacent limbleads.



Diagnosis?



One or more of the precordial leads (V1-V6) and leads I

and aVL suggest anterior wall ischemia or infarction

Leads V4 to V6 suggest apical or lateral ischemia or

infarction



Diagnosis?



Leads V1 to V3 suggest

anteroseptal ischemia or infarction.







Diagnosis?



Leads II, III, and aVF suggest inferior

wall ischemia or infarction





Diagnosis?



Acute infero-postero-lateral myocardialinfarction

1. ST depression in V2 and V3 (posteriorwall MI)

2. ST elevation in II, III and aVF (inferiorwall MI)

3. T wave inversion in V4-6 (lateral wall MI)



Posterior wall MI

The ST elevations of acute posterior MIare usually associated with reciprocal STdepressions in leads V1 to V3.

Posterior inferior wall MI can bedifferentiated from anterior wall ischemiaby the presence of ST segment elevationsin the inferior (II, III, aVF). Relatively tallR waves may also appear in leads V1-V3,corresponding to the appearance of pathologic Q waves (loss of depolarizationforces) in the posterior leads.





Diagnosis?



Ischemia

ST depression is defined by an STsegment which is depressed >1 mmbelow the baseline

Typically there are ST segmentchanges associated with T waveflattening or inversion; isolated T

wave changes are not usually seenwith ischemia.



Diagnosis?



New LBBB: Treat as ST Elevation

MI i.e. rush to cath lab for PCI

LBBB Diagnosis:Slurring of S wave in V5 and V6 and

QRS duration > 100 msec (i.e more than 2½ small squares)



Abnormal Q wave

According to the new criteria, anabnormal Q wave is any Q wave inleads V1 to V3 or a Q wave 30 msec

in leads I, II, aVL, aVF, or V4 to V6;the Q wave must be present in anytwo contiguous leads and 1 mm in

depth.(European Society of Cardiology (ESC) and

American College of Cardiology (ACC) 2000)



Diagnosis?



Ventricular Tachycardia

Tachycardia

Wide complex

Regular





Atrial Fibrillation:•Absent P waves

•Irregulary irregular rhythm









Sinus rhythm with complete (third-degree) heart block. There is independentatrial (as shown by the P waves) andventricular activity, with respective ratesof 83 and 43 beats/min.





Mobitz type I (Wenckebach) seconddegree AV block

A progressively increasing PRinterval until a P wave is notconducted (arrow)



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