ELECTROCARDIOGRELECTROCARDIOGRAMAM

Marco Christopher G. Marco Christopher G. Montaos, MD.Montaos, MD.

Internal MedicineInternal Medicine

ELECTROCARDIOGRAMELECTROCARDIOGRAM

is a graphical record of electric is a graphical record of electric potentials generated by the heart muscle potentials generated by the heart muscle during each cardiac cycle. The signals during each cardiac cycle. The signals are detected on the surface of the body are detected on the surface of the body using electrodes attached to the using electrodes attached to the extremities and chest wall. These signals extremities and chest wall. These signals are then amplified by the are then amplified by the electrocardiograph machine and electrocardiograph machine and displayed on special graph paper.displayed on special graph paper.

Indications :Indications : RateRate RhythmRhythm AxisAxis HypertrophyHypertrophy Ischemic or InfarctionIschemic or Infarction

Indications for ordering an Indications for ordering an electrocardiogramelectrocardiogram

1. To determine cardiac rate1. To determine cardiac rate

2. To accurately define cardiac rhythm2. To accurately define cardiac rhythm

3. To diagnose old or new myocardial 3. To diagnose old or new myocardial infarctioninfarction

4. To identify intracardiac conduction 4. To identify intracardiac conduction disturbancesdisturbances

5. To aid in the diagnosis of ischemic 5. To aid in the diagnosis of ischemic heart disease, pericarditis, heart disease, pericarditis, myocarditis, electrolyte abnormalities myocarditis, electrolyte abnormalities and pacemaker malfunctionand pacemaker malfunction

Position of the chest leadsPosition of the chest leads

LeadsLeads Position in the chestPosition in the chestV1V1 4th ICS at the right sternal border4th ICS at the right sternal borderV2V2 4th ICS at the left sternal border4th ICS at the left sternal borderV3V3 Halfway between V2 and V4Halfway between V2 and V4V4V4 5th ICS at the left midclavicular line5th ICS at the left midclavicular lineV5V5 5th ICS at the left anterior axillary line5th ICS at the left anterior axillary lineV6V6 5th ICS at the left mid-axillary line5th ICS at the left mid-axillary lineV3RV3R Halfway between V1 and V4RHalfway between V1 and V4RV4RV4R 5th ICS at the right midclavicular line5th ICS at the right midclavicular line

I. RateI. RateA. Rate Interpretation has three A. Rate Interpretation has three

possibilities:possibilities:1. Bradycardia - (< 60 beats/min.)1. Bradycardia - (< 60 beats/min.)2.Normal Rate – ( 60 – 100 beats per 2.Normal Rate – ( 60 – 100 beats per minute )minute )3. Tachycardia – ( > 100 beats per minute )3. Tachycardia – ( > 100 beats per minute )

B. Rate Analysis:B. Rate Analysis:Mnemonic: Memorize “ 300,150,100…Mnemonic: Memorize “ 300,150,100…

75,60,50”75,60,50”= if R to R interval > 5 big squares: = if R to R interval > 5 big squares:

BradycardiaBradycardia= if R to R interval between 3-5 big squares: = if R to R interval between 3-5 big squares:

Normal RateNormal Rate= if R to R interval < 3 big squares: = if R to R interval < 3 big squares:

TachycardiaTachycardia

FORMULAFORMULA

Heart Rate = 1500 or Heart Rate = 1500 or 300 300 ------------ ------------ ------------- -------------

# of small boxes # of # of small boxes # of big boxesbig boxes

II. RHYTHMII. RHYTHM

A. Common Rhythm Interpretations:A. Common Rhythm Interpretations:

1. Sinus Rhythm1. Sinus Rhythm

2. Common Supraventricular 2. Common Supraventricular Arrythmias:Arrythmias:

a. Atrial Fibrillationa. Atrial Fibrillation

b. Atrial Flutterb. Atrial Flutter

c. Supraventricular c. Supraventricular TachycardiaTachycardia

3. Heart Blocks3. Heart Blocks a. First degree AV blocka. First degree AV block b. Second degree AV block Mobitz type I b. Second degree AV block Mobitz type I

( Wenckebach )( Wenckebach ) c. Second degree AV block Mobitz type IIc. Second degree AV block Mobitz type II d. Third degree AV blockd. Third degree AV block e. Left or Right Bundle Branch Block e. Left or Right Bundle Branch Block

( complete and incomplete )( complete and incomplete )

4. Ventricular Arrythmias4. Ventricular Arrythmias a. Premature Ventricular Contractionsa. Premature Ventricular Contractions b. Ventricular Tachycardia ( sustained and b. Ventricular Tachycardia ( sustained and

unsustained )unsustained ) c. Ventricular Fibrillation c. Ventricular Fibrillation

B. Rhythm Analysis:B. Rhythm Analysis:1. Identify the P wave1. Identify the P wave Determine from the configuration if this is a sinus PDetermine from the configuration if this is a sinus P2. Check the relation of P wave to QRS2. Check the relation of P wave to QRSa. P wave is before QRS ( normal )a. P wave is before QRS ( normal )b. P wave is buried or after QRS ( e.g. SVT, complete heart b. P wave is buried or after QRS ( e.g. SVT, complete heart

block )block )3. Check PR interval ( Normal PR interval: 0.12 – 0.20 sec. )3. Check PR interval ( Normal PR interval: 0.12 – 0.20 sec. )a. Short PR ( WPW syndrome )a. Short PR ( WPW syndrome )b. Normal PR b. Normal PR c. Prolonged PR ( 1st or 2nd degree AV block )c. Prolonged PR ( 1st or 2nd degree AV block )4. Check QRS duration ( Normal QRS duration < 0.10 sec. )4. Check QRS duration ( Normal QRS duration < 0.10 sec. )a. Normal QRSa. Normal QRSb. Wide QRS ( Bundle branch blocks )b. Wide QRS ( Bundle branch blocks )5. Check the relation of R-R and P-P interval5. Check the relation of R-R and P-P intervala. Equal R-R and P-P interval ( Normal )a. Equal R-R and P-P interval ( Normal )b. P-P interval shorter than R-R interval ( Complete heart b. P-P interval shorter than R-R interval ( Complete heart

block )block )c. P-P interval longer than R-R interval ( AV dissociation )c. P-P interval longer than R-R interval ( AV dissociation )

III. AXISIII. AXIS

A. Axis Interpretation has Four A. Axis Interpretation has Four Possibilities:Possibilities:

1.Normal Axis1.Normal Axis

2. Left Axis Deviation ( LAD )2. Left Axis Deviation ( LAD )

3. Right Axis Deviation ( RAD )3. Right Axis Deviation ( RAD )

4. Indeterminate Axis4. Indeterminate Axis

B. Axis Analysis:B. Axis Analysis:

Getting the Axis DeviationGetting the Axis Deviation

( + ) QRS deflection: Average ( + ) QRS deflection: Average QRS vector above the baseline in QRS vector above the baseline in leads I or AVFleads I or AVF

( - ) QRS deflection: Average QRS ( - ) QRS deflection: Average QRS vector below the baseline in vector below the baseline in leads I or AVFleads I or AVF

Normal AxisNormal Axis ++ ++

Left Axis Left Axis DeviationDeviation

++ --

Right Axis Right Axis DeviationDeviation

-- ++

Indeterminate Indeterminate AxisAxis

-- --

LEAD I LEAD AVF

Differential diagnosis for left and Differential diagnosis for left and right axis deviationright axis deviation

QRS Left Axis DeviationQRS Left Axis Deviation

1.1. normal variant ( short normal variant ( short fat individuals)fat individuals)

2. left ventricular 2. left ventricular hypertrophyhypertrophy

3. inferior wall infarction3. inferior wall infarction

4. left bundle branch 4. left bundle branch blockblock

5. left anterior fascicular 5. left anterior fascicular blockblock

6. WPW syndrome6. WPW syndrome

QRS Right Axis DeviationQRS Right Axis Deviation

1.1. normal variant (thin tall normal variant (thin tall individuals)individuals)

2. right ventricular 2. right ventricular hypertrophyhypertrophy

3. lateral wall infarction3. lateral wall infarction

4. pulmonary embolism4. pulmonary embolism

5. left posterior fascicular 5. left posterior fascicular blockblock

6. WPW syndrome6. WPW syndrome

IV. HypertrophyIV. HypertrophyA. Hypertrophy interpretation has A. Hypertrophy interpretation has

6 possibilities:6 possibilities:1.1. no hypertrophyno hypertrophy2.2. LVHLVH3.3. RVHRVH4.4. LAELAE5.5. RAERAE6.6. a combination of the abovea combination of the above

B. Hypertrophy analysis:B. Hypertrophy analysis:Three LVH ECG Criteria: these are Three LVH ECG Criteria: these are

distorted by the presence of a distorted by the presence of a complete LBBB but not by complete complete LBBB but not by complete RBBBRBBB

1. S wave in V1 + R wave in v5 or v6 > 1. S wave in V1 + R wave in v5 or v6 > 35mm (commonly used)35mm (commonly used)

sensitivity 43%, Specificity 97%sensitivity 43%, Specificity 97%2. R in AVL > 11mm2. R in AVL > 11mm

sensitivity 11%, specificity 100%sensitivity 11%, specificity 100%3. Romhilt and Estes Criteria (Best 3. Romhilt and Estes Criteria (Best

Criteria)Criteria)sensitivity 50%, specificity 95%sensitivity 50%, specificity 95%

a. amplitudea. amplitude 3 points3 points

largest R or S wave in the limb leads largest R or S wave in the limb leads >= 20mm>= 20mm

s wave in v1 or v2 >= 30mms wave in v1 or v2 >= 30mm

r wave in v5 or v6 >= 30mmr wave in v5 or v6 >= 30mm

b. ST-T segment changes typical of LV b. ST-T segment changes typical of LV strain patternstrain pattern

without digitaliswithout digitalis 3 3 pointspoints

with digitaliswith digitalis 1 point1 point

c. LAE: terminal negativity c. LAE: terminal negativity 3points3points

of the P wave in v1 is of the P wave in v1 is

1mm or more in depth 1mm or more in depth

with a duration of 0.04s or morewith a duration of 0.04s or more

d. LAD: 30 degrees or mored. LAD: 30 degrees or more 2 points2 points

e. QRS duration >= 0.09s but < 0.12se. QRS duration >= 0.09s but < 0.12s 1 1 pointpoint

f. intrinsicoid deflectionf. intrinsicoid deflection 1 point1 point

in v5 and v6 >= 0.05sin v5 and v6 >= 0.05s

interpretation of total score:interpretation of total score: possible possible LVH 3 pointsLVH 3 points

probable LVH probable LVH 4points4points

definitive LVH definitive LVH >= 5 \>= 5 \

pointspoints

Four RVH ECG CriteriaFour RVH ECG Criteria

1. right axis deviation of 110 1. right axis deviation of 110 degrees or more, with any of the degrees or more, with any of the ffff

2. lead v1 R wave > S wave2. lead v1 R wave > S wave

3. deep s wave in v5 and v63. deep s wave in v5 and v6

4. ST depression and t wave 4. ST depression and t wave inversion in v1-v3inversion in v1-v3

LAE ECG criteria: any of the ffLAE ECG criteria: any of the ff

1. v1: wide terminal component of 1. v1: wide terminal component of P wave which is >= 1mm wide P wave which is >= 1mm wide and>= 1mm deepand>= 1mm deep

2. in any lead: P wave wider than 2. in any lead: P wave wider than 0.12s or with a >= 1mm notch 0.12s or with a >= 1mm notch in the middlein the middle

RAE ECG criteria: any of the ffRAE ECG criteria: any of the ff

1. v1: tall initial component of P 1. v1: tall initial component of P wave which is >= 2mm wide and wave which is >= 2mm wide and >= 2mm tall>= 2mm tall

2. in any lead: P wave >= 2.5mm 2. in any lead: P wave >= 2.5mm talltall

Biventricular Hypertrophy Biventricular Hypertrophy Diagnostic ECG criteria: any of Diagnostic ECG criteria: any of

the ffthe ff1.1. the ECG meets one or more of the ECG meets one or more of

the diagnostic criteria for the diagnostic criteria for isolated left and right isolated left and right ventricular hypertrophyventricular hypertrophy

2.2. the precordial leads show signs the precordial leads show signs of left ventricular hypertrophy, of left ventricular hypertrophy, but the QRS axis in the frontal but the QRS axis in the frontal plane is > 90 degreesplane is > 90 degrees

Biatrial enlargement Biatrial enlargement diagnostic ECG criteriadiagnostic ECG criteria

1.1. v1: presence of a large diphasic P v1: presence of a large diphasic P wave with the initial positive wave with the initial positive component >= 2mm tall and the component >= 2mm tall and the terminal negative component >= terminal negative component >= 1mm deep and >= 0.04s in duration1mm deep and >= 0.04s in duration

2.2. in any lead: increase in both the in any lead: increase in both the amplitude which is 2.5mm or greater amplitude which is 2.5mm or greater and duration of 0.12s or more of the and duration of 0.12s or more of the P waveP wave

V. Ischemia and InfarctionV. Ischemia and Infarction

A. interpretation has 4 possibilities:A. interpretation has 4 possibilities:

1.1. within normal limits (WNL). 50% within normal limits (WNL). 50% of patients w/ CAD or chronic of patients w/ CAD or chronic stable angina have normal ECGsstable angina have normal ECGs

2.2. non-specific ST-T wave changesnon-specific ST-T wave changes

3.3. myocardial ischemia changesmyocardial ischemia changes

4.4. myocardial infarction changesmyocardial infarction changes

B. Infarction and Ischemia analysis

Leads involvedLeads involved Corresponding Corresponding AreasAreas

II, III, AVFII, III, AVF Inferior wallInferior wall

I, AVLI, AVL High lateral wallHigh lateral wall

V1,v2V1,v2 Septal wallSeptal wall

V3, v4V3, v4 Anterior wallAnterior wall

V5, v6V5, v6 Lateral wallLateral wall

V1-v3V1-v3 Anteroseptal wallAnteroseptal wall

V3-v6, I, AVLV3-v6, I, AVL Anterolateral wallAnterolateral wall

V5, v6, II, III, AVFV5, v6, II, III, AVF Inferolateral wallInferolateral wall

Almost all leadsAlmost all leads Diffuse, global, Diffuse, global, massivemassive

Mirror image of Mirror image of v1, v2v1, v2

Posterior LV wallPosterior LV wall

V3R, v4RV3R, v4R RV wallRV wall

ECG findings in ischemia:ECG findings in ischemia:

1.1. at least 1mm ST-segment at least 1mm ST-segment depressiondepression

2.2. symmetrically inverted t wavesymmetrically inverted t wave

3.3. abnormallt tall T waveabnormallt tall T wave

4.4. normalization of abnormal T wavenormalization of abnormal T wave

5.5. prolonged QT intervalprolonged QT interval

6.6. arrhythmia, bundle branch arrhythmia, bundle branch blocks, AV blocksblocks, AV blocks

ECG criteria for infarct:ECG criteria for infarct:

1.1. ST elevation >= 2mm in 2 or more ST elevation >= 2mm in 2 or more chest leads or >= 1mm in 2 or chest leads or >= 1mm in 2 or more limb leadsmore limb leads

2.2. Q waves >= 0.04sQ waves >= 0.04s

Myocardial Infarction In the presence Myocardial Infarction In the presence of BBBsof BBBs

1.1. RBBB: usual myocardial criteriaRBBB: usual myocardial criteria

2.2. LBBB: diminishing R wave forces LBBB: diminishing R wave forces in the precordial leads or Q waves in the precordial leads or Q waves at v5 and v6at v5 and v6

Patterns that may mimic Patterns that may mimic MI:MI:

1.1. complete LBBBcomplete LBBB2.2. early repolarization patternearly repolarization pattern3.3. LV aneurysmLV aneurysm4.4. hyperkalemiahyperkalemia5.5. pericarditispericarditis6.6. intracranial hemorrhageintracranial hemorrhage7.7. idiopathic subaortic stenosisidiopathic subaortic stenosis8.8. WPW syndromeWPW syndrome9.9. electronic pacing of right ventricleelectronic pacing of right ventricle10.10. pulmonary disorderspulmonary disorders

VI. Miscellaneous ECG VI. Miscellaneous ECG findings:findings:

1.1. hypokalemiahypokalemia U wave as tall or taller than the T wave at U wave as tall or taller than the T wave at

leads v2 v3. leads v2 v3. 2.2. hyperkalemiahyperkalemia

in the chest leads, height of T waves >10mm in the chest leads, height of T waves >10mm in most leads. in most leads.

In the limb leads, height of T waves > 5mm in In the limb leads, height of T waves > 5mm in most leads.most leads.

3.3. hypocalcemiahypocalcemia prolonged QT interval ( normal QT interval is prolonged QT interval ( normal QT interval is

less than half the RR interval)less than half the RR interval)4.4. hypercalcemiahypercalcemia

shortened QT intervalshortened QT interval5.5. digitalis effectdigitalis effect

manifested by prolonged PR interval, manifested by prolonged PR interval, scooping of the ST segment, and short QT scooping of the ST segment, and short QT intervalinterval

6. digitalis toxicity6. digitalis toxicity all types of arrythmias, usually PVC’s or paroxysmal all types of arrythmias, usually PVC’s or paroxysmal

atrial tachycardiaatrial tachycardia

7. electrical alternans of QRS complex7. electrical alternans of QRS complex height of QRS varies from beat to beatheight of QRS varies from beat to beat may be due to cardiac tamponade, large pericardial may be due to cardiac tamponade, large pericardial

effusion, low cardiac output, COPD, tension effusion, low cardiac output, COPD, tension pneumothoraxpneumothorax

8. poor R wave progression8. poor R wave progression height of the R wave in v3 is < 3mmheight of the R wave in v3 is < 3mm may be due to old anteroseptal wall MI, LVH, normal may be due to old anteroseptal wall MI, LVH, normal

variant of a heart rotated clockwise, LBBBvariant of a heart rotated clockwise, LBBB

9. persistent S wave in v5 v69. persistent S wave in v5 v6 prominent S waves in v5 and v6prominent S waves in v5 and v6 my be die to RVH, or the heart rotated clockwisemy be die to RVH, or the heart rotated clockwise

10. early repolarization changes10. early repolarization changes normal variant in young males (ST segment elevation normal variant in young males (ST segment elevation

of 2-3mm in leads v2-v4 usually found in males <40yrs of 2-3mm in leads v2-v4 usually found in males <40yrs old)old)

may be due to Acute anteroseptal wall MI, or acute may be due to Acute anteroseptal wall MI, or acute pericarditispericarditis

11. juvenile T wave inversion11. juvenile T wave inversion normal variant in young females (T wave inversion normal variant in young females (T wave inversion

in v1-v3 in females <30yrs old)in v1-v3 in females <30yrs old) may be due to acute anteroseptal wall ischemiamay be due to acute anteroseptal wall ischemia

12. low voltage QRS complexes12. low voltage QRS complexes the amplitude of the entire QRS complex in all the the amplitude of the entire QRS complex in all the

limb leads is <5mmlimb leads is <5mm may be found in normal elderly patients, obese or may be found in normal elderly patients, obese or

edematous patients, cardiac tamponade, large edematous patients, cardiac tamponade, large pericardial effusion, pneumothorax, pericardial effusion, pneumothorax, hypothyroidism, dilated cardiomyopathy.hypothyroidism, dilated cardiomyopathy.

13. high voltage QRS complexes13. high voltage QRS complexes large QRS complexeslarge QRS complexes may be found in patients <35yrs old, LVH, RVH, may be found in patients <35yrs old, LVH, RVH,

LBBB, RBBBLBBB, RBBB14. cerebral T waves of intracranial hemorrhage14. cerebral T waves of intracranial hemorrhage

wide, prominent, and deeply inverted T waves with wide, prominent, and deeply inverted T waves with a long QT intervala long QT interval

may be found in intracranial hemorrhage, may be found in intracranial hemorrhage, subendocardial MI, and MIsubendocardial MI, and MI

15. wrong lead placement15. wrong lead placement an upright P wave in lead AVR an upright P wave in lead AVR

accompanied by a normal R wave accompanied by a normal R wave progression in the precordial leadsprogression in the precordial leads

16. wrong speed16. wrong speed widened PR and QRS intervals and the widened PR and QRS intervals and the

patient’s heart rate does not jive with patient’s heart rate does not jive with the ECG heart rate.the ECG heart rate.

Speed used is 50mm/sec instead of the Speed used is 50mm/sec instead of the usual 25mm/secusual 25mm/sec

17. artifacts17. artifacts irregular spikes or undulations on the irregular spikes or undulations on the

ECG baseline are not found in the other ECG baseline are not found in the other segments.segments.