Ecg interpretation

ECG Interpretation for ECG Interpretation for Primary Care PhysicianPrimary Care Physician

Aamir A. Cheema M.D.Aamir A. Cheema M.D.

WelcomeWelcome PPakistan akistan SSociety of ociety of FFamily amily PPhysicianshysicians

ECG GridECG Grid

6 Steps6 Steps

1.1. RateRate

2.2. RhythmRhythm

3.3. AxisAxis

4.4. IntervalsIntervals

5.5. HypertrophyHypertrophy

6.6. Infarction/IschemiaInfarction/Ischemia

Rate Rate

300-150-100-75-60-50

300-150-100-75-60-50

What if rate is <50/min or rhythm is What if rate is <50/min or rhythm is irregular ?irregular ?

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

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

RhythmRhythm

1. Locate the P wave1. Locate the P wave If absent and rhythm is irregular, think of atrial fibrillation.If absent and rhythm is irregular, think of atrial fibrillation. If present- check rate: If <60, bradycardia. If >100, If present- check rate: If <60, bradycardia. If >100,

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

heart rate is heart rate is

100-150, think of sinus tachycardia100-150, think of sinus tachycardia

150-250, think of SVT (supraventricular tachycardia)150-250, think of SVT (supraventricular tachycardia)

250-350, think of atrial flutter250-350, think of atrial flutter

>350, think of atrial fibrillation>350, think of atrial fibrillation

RhythmRhythm

2. Establish the relationship between P 2. Establish the relationship between P wave and QRS complexwave and QRS complex

If 1:1, it is normalIf 1:1, it is normal If more P waves than QRS If more P waves than QRS

complexes, think of AV blockcomplexes, think of AV block If more QRS complexes than P If more QRS complexes than P

waves, think of accelerated waves, think of accelerated junctional or ventricular rhythmjunctional or ventricular rhythm

RhythmRhythm

3. Analyze the QRS morphology3. Analyze the QRS morphology If normal duration (<120 msec), If normal duration (<120 msec),

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

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

AxisAxis

IntervalsIntervals

PR interval: <200 msec (one big box)

QRS complex:<100 msec (2½ small boxes)

ST segment: evaluate for elevation or depression

below baselineQT segment: roughly less than half of R-R interval

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

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

HypertrophyHypertrophy

Left ventricular hypertrophy criteriaLeft ventricular hypertrophy criteria

Sum of S wave in V1 and R wave in Sum of S wave in V1 and R wave in V5 or V6 3.5 mV (35 mm) V5 or V6 3.5 mV (35 mm)

        and/or and/or

R wave in aVL 1.1 mV (11 mm) R wave in aVL 1.1 mV (11 mm)

Normal ECGNormal ECG

InfarctionInfarction

Clinically significant ST segment Clinically significant ST segment elevation is considered to be present elevation is considered to be present if it is greater than 1 mm (0.1 mV) in if it is greater than 1 mm (0.1 mV) in at least two contiguous precordial at least two contiguous precordial leads or in at least two adjacent limb leads or in at least two adjacent limb leads. leads.

Diagnosis?Diagnosis?

One or more of the precordial leads (V1-V6) and leads I One or more of the precordial leads (V1-V6) and leads I and aVL suggest anterior wall ischemia or infarctionand aVL suggest anterior wall ischemia or infarctionLeads V4 to V6 suggest apical or lateral ischemia or Leads V4 to V6 suggest apical or lateral ischemia or

infarctioninfarction

Diagnosis?Diagnosis?

Leads V1 to V3 suggest Leads V1 to V3 suggest anteroseptal ischemia or infarction.anteroseptal ischemia or infarction.

Diagnosis?Diagnosis?

Leads II, III, and aVF suggest inferior Leads II, III, and aVF suggest inferior wall ischemia or infarctionwall ischemia or infarction

Diagnosis?Diagnosis?

Acute infero-postero-lateral myocardial Acute infero-postero-lateral myocardial infarctioninfarction

1.1. ST depression in V2 and V3 (posterior ST depression in V2 and V3 (posterior wall MI)wall MI)

2.2. ST elevation in II, III and aVF (inferior wall ST elevation in II, III and aVF (inferior wall MI)MI)

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

Posterior wall MIPosterior wall MI

The ST elevations of acute posterior MI are The ST elevations of acute posterior MI are usually associated with reciprocal ST usually associated with reciprocal ST depressions in leads V1 to V3. depressions in leads V1 to V3.

Posterior inferior wall MI can be Posterior inferior wall MI can be differentiated from anterior wall ischemia differentiated from anterior wall ischemia by the presence of ST segment elevations by the presence of ST segment elevations in the inferior (II, III, aVF). Relatively tall R in the inferior (II, III, aVF). Relatively tall R waves may also appear in leads V1-V3, waves may also appear in leads V1-V3, corresponding to the appearance of corresponding to the appearance of pathologic Q waves (loss of depolarization pathologic Q waves (loss of depolarization forces) in the posterior leads. forces) in the posterior leads.

Diagnosis?Diagnosis?

Ischemia Ischemia

ST depression is defined by an ST ST depression is defined by an ST segment which is depressed >1 mm segment which is depressed >1 mm below the baseline below the baseline

Typically there are ST segment Typically there are ST segment changes associated with T wave changes associated with T wave flattening or inversion; isolated T flattening or inversion; isolated T wave changes are not usually seen wave changes are not usually seen with ischemia. with ischemia.

Diagnosis?Diagnosis?

NewNew LBBB: Treat as ST Elevation LBBB: Treat as ST Elevation MI i.e. rush to cath lab for PCIMI 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 waveAbnormal Q wave

According to the new criteria, an According to the new criteria, an abnormal Q wave is any Q wave in abnormal Q wave is any Q wave in leads V1 to V3 or a Q wave 30 msec leads V1 to V3 or a Q wave 30 msec in leads I, II, aVL, aVF, or V4 to V6; in leads I, II, aVL, aVF, or V4 to V6; the Q wave must be present in any the Q wave must be present in any two contiguous leads and 1 mm in two contiguous leads and 1 mm in depth. depth.

(European Society of Cardiology (ESC) and (European Society of Cardiology (ESC) and American College of Cardiology (ACC) 2000)American College of Cardiology (ACC) 2000)

Diagnosis?Diagnosis?

Ventricular TachycardiaVentricular Tachycardia TachycardiaTachycardia Wide complexWide complex RegularRegular

Atrial Fibrillation:•Absent P waves

•Irregulary irregular rhythm

Sinus rhythm with complete (third-degree) Sinus rhythm with complete (third-degree) heart block. There is independent atrial (as heart block. There is independent atrial (as shown by the P waves) and ventricular shown by the P waves) and ventricular activity, with respective rates of 83 and 43 activity, with respective rates of 83 and 43 beats/min. beats/min.

Mobitz type I (Wenckebach) second Mobitz type I (Wenckebach) second degree AV block degree AV block

A progressively increasing PR A progressively increasing PR interval until a P wave is not interval until a P wave is not conducted (arrow) conducted (arrow)

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