basic of ecg and easy interpretation

BASICS OF ELECTROCARDIOGRAPHY

Dr Mushfiq Newaz Ahmed Medical Officer Department Of Anaesthesia, Comilla Medical College & Hospital

OUTLINE1. Review of the conduction system & Action Potential2. ECG leads and recording 3. ECG waveforms and intervals4. Normal ECG and its variants5. Basic Interpretation Steps of ECG6. Arrhythmia & ECG7. MI & ECG8. EI & ECG9. Thyroid Disorder & ECG10. Emergency ECG

ACTION POTENTIAL OF CARDIAC CELL

BUT THE IRONY OF FATE IS……

WHAT IS AN ECG?

An ECG is the recording (gram) of the electrical activity(electro) generated by the cells of the heart(cardio) that reaches the body surface.

USEFUL IN DIAGNOSIS OF…

Cardiac Arrhythmias Myocardial ischemia and infarction Pericarditis Chamber hypertrophy Electrolyte disturbances

ECG LEADS

ECG LEADSLeads are electrodes which measure the difference in electrical potential between either:

1. Two different points on the body (bipolar leads)

2. One point on the body and a virtual reference point with zero electrical potential, located in

the center of the heart (unipolar leads)

ECG LEADS

The standard ECG has 12 leads: 3 Standard Limb Leads

3 Augmented Limb Leads

6 Precordial Leads

The axis of a particular lead represents the viewpoint from which it looks at the heart

STANDARD LIMB LEADS

EINTHOVEN’S TRIANGLE

PRECORDIAL LEADS

PRECORDIAL LEADS

SUMMARY OF LEADS

Limb Leads Precordial Leads

Bipolar I, II, III(standard limb leads)

-

Unipolar aVR, aVL, aVF (aug-mented limb leads)

V1-V6

ANATOMIC GROUPS(SEPTUM)

ANATOMIC GROUPS(ANTERIOR WALL)

ANATOMIC GROUPS(LATERAL WALL)

ANATOMIC GROUPS(INFERIOR WALL)

ANATOMIC GROUPS(SUMMARY)

Localising the arterial territory

InferiorII, III, aVF

LateralI, AVL, V5-V6

Anterior / SeptalV1-V4

SPECIAL SITUATION Amputation or burns or bandages should be placed

as closely as possible to the standard sites

Dextrocardia right & left arm electrodes should be re-versedpre-cordial leads should be recorded from V1R(V2) to V6

OTHER PRACTICAL POINTS

Effective contact between electrode and skin is essen-tial.

Electrical Artifacts: external or internal-External can be minimized by straightening the lead

wires-Internal can be due to muscle tremors, shivering ,

hiccups

ECG PAPER

ECG PAPER BASICSECG graphs:– Small Square -Height 1 mm and width 0.04 s– Large Square -Height 5 mm and width 0.04X5=0.2s Paper Speed:– 25 mm/s( As 0.2 s=5 mm,1 s=25 mm)Voltage Calibration: – 1 mV= П 10 mm( 10 small square) Half strength 5mm/mV Double strength 20 mm/mV

ECG PAPER BASICS

ECG WAVES

WAVE FORMS

P WAVE Denotes Atrial depolarization Shape-Rounded, neither peaked nor notched Width/Duration-2.5 small sq Height-2.5 small sq Better seen in Lead II/Lead V1 Upright in every lead except aVR May be Biphasic in lead V1(Equal upward and downward

deflection)

PR INTERVAL Distance between onset of P wave to the beginning of Q

wave(in absence of Q wave beginning of R wave) Denotes time interval impulse travelling from SA node to

Ventricular muscle through AV node Normal Range:3 to 5 small Sq Short if ‹3 small sq and long if ›5 small sq

NORMAL QRS COMPLEX Denotes Ventricular depolarization Normal width of QRS-2 to ‹3 small sq Narrow complex if less than 2 small sq and

Broad Complex if more than or equal to 3 small sq

COMPONENT OF QRS COMPLEXo Q wave-width 1 small sq and depth 2 small sq and ‹25%

of following R wave (Pathological if width›1 small sq,depth›2 small sq and

›25% of following R Wave)o R wave height varies, but must remember the thing that

R wave progresses from V1 to V6(2-3 small square to les than 25 small sq/5 large sq)

(Pathological if height›25 small sq/5 large sq)o S wave follow R wave, depth varies,progressively dimin-

ishes from V1 to V6

T WAVE Same direction as the preceding QRS complex Blunt apex with asymmetric limbs Height < 5 small sq in limb leads and <10 small square in

precordial leads Smooth contours May be tall in athletes

ST SEGMENT

Merges smoothly with the proximal limb of the T wave No true horizontality

QT INTERVAL Distance between beginning of QRS to the end Of T

wave Reciprocal relation with heart rate Normal 8-‹11 small sq If arrhythmia is present( HR less than 60 or more than

100 bpm) then QT interval should be corrected. Corrected QT(QTc)=QT/√RR

U WAVE Best seen in midprecordial leads Height < 10% of preceding T wave Isoelectric in lead aVL (useful to measure QTc) Rarely exceeds 1 small sq in amplitude May be tall in athletes (2 small sq)

HEART RATE, RHYTHM AND AXIS

DETERMINING THE HEART RATE

Rule of 300

10 times/20 times method

RULE OF 300Take the number of “Large Square” between neighboring QRS complexes, and divide this into 300. More accuracy can be achieved if the number of “small square” between neighboring QRS complexes divided into 1500

Although fast, this method only works for regular rhythms.

RULE OF 300It may be easiest to memorize the following table:

Number of large square

Rate

1 300

2 150

3 100

4 75

5 60

6 50

7 43

10 TIMES/20 TIMES RULE

Count the number of R in 30 large square(equivalent to 6 second) and multiply it by 10 would become rate in 60 sec. If small strip-counting the number in 15 large square(equivalent to 3 second) and multiply it by 20

This method works well for irregular rhythms.

DETERMINING RHYTHM

AXIS DETERMINATION

The QRS axis represents the net overall direction of the heart’s electrical activity.

Abnormalities of axis can hint at:Ventricular enlargementConduction blocks (i.e. hemiblocks)

THE QRS AXISBy near-consensus, the nor-mal QRS axis is defined as ranging from -30° to +90°.

-30° to -90° is referred to as a left axis deviation (LAD)

+90° to +180° is referred to as a right axis deviation (RAD)

DETERMINING THE AXIS

The Quadrant Method

The Degree Method

THE QUADRANT METHODExamine the QRS complex in lead I/lead aVL and lead III/lead aVF to determine if they are predominantly positive or predominantly negative. The combination should place the axis into one of the 4 quadrants below.

COMMON CAUSES OF LAD May be normal in the elderly and very obese Due to high diaphragm during pregnancy or ascites Inferior wall MI Left Anterior Hemi block Left Bundle Branch Block Emphysema

COMMON CAUSES OF RAD Normal variant Right Ventricular Hypertrophy Anterior MI Right Bundle Branch Block Left Posterior Hemiblock

THE NORMAL ECG & VARIATION WITH RESPIRA-TION

NORMAL SINUS RHYTHM Originates in the sinus node Rate between 60 and 100 beats per min Monomorphic P waves Normal relationship between P and QRS Some sinus arrhythmia is normal

APPROACH TO INTERPRET

STEP-1:LEAD POSITIONNormal-P wave upright in lead I & II and QRS should be

downward in aVR & V1, R wave progresses from V1 to V6(height increases)

Lead Malposition-P wave downward in lead I & II and QRS should be upright in aVR & V1, R wave progresses from V1 to V6(height increases)

Dextrocardia- P wave downward in lead I & II and QRS should be upright in aVR & V1, R wave regresses from V1 to V6(height decreases)

Lead Malposition

Dextrocardia

STEP 2: VOLTAGE OR AMPLITUDE Normal ECG paper- voltage or amplitude 10 mV Half Voltage,5 mV used specially when severe LVH causes very

large QRS complex which merges with QRS complexes of above or below leads

Electrical Alternans-Alternate beat variation in direction, ampli-tude and duration of any component of ECG. It can be found in-Pericardial Effusion, Pericardial Mesothelioma, Pericardial TB, Myocarditis, Hypothermia

STEP 3:RHYTHM & RATE Rhythm Assessment- By Paper & Pencil Method or

Caliper Method

Rate Measurement-By 300 times method/20 times method

STEP 4: AXIS Normal- QRS of lead I(+aVL) and QRS of lead II+(III &

aVF) is in the same direction

LAD- QRS of lead I(+aVL) upward and QRS of lead II+(III & aVF) downward

RAD- QRS of lead I(+aVL) downward and QRS of lead II+(III & aVF) upward

Negative in I, positive in aVF RAD

Positive in I, negative in aVF LAD

STEP 5: BUNDLE BRANCH BLOCK(CLUE: WIDE QRS)

RBBB- M pattern in QRS in Lead V1( or V2/V3). May be nor-mal

LBBB-M pattern in QRS in Lead V6( or V4/V5). T inversion can be found. New onset always Alarming

Bifascicular block- RBBB+ Left posterior Hemiblock----›features of

RBBB+RAD(Ostium Secundum ASD) RBBB+ Left anterior Hemiblock ----›features of

RBBB+LAD(Ostium Primum ASD)

RIGHT MARROW(RBBB) LEFT WILLOW( LBBB)

STEP 6:CHAMBER ENLARGEMENT Right Atrial Enlargement- Tall peaked P wave

Left Atrial Enlargement-Broad/M Pattern/Wide/Bifid or notched P wave

Right Ventricular Enlargement-Tall R in V1 and deep S in V5/V6

Left Ventricular Enlargement-Unusually tall R in V5/V6 and unusually deep S in V1(R+S>35 mm)

RIGHT ATRIAL ENLARGEMENT

LEFT ATRIAL ENLARGEMENT

RIGHT VENTRICULAR HYPERTRO-PHY

RIGHT VENTRICULAR HYPERTRO-PHY

LEFT VENTRICULAR HYPERTRO-PHY

LEFT VENTRICULAR HYPERTRO-PHY

7. WAVE & INTERVAL ABNORMALITY

P WAVE ABNORMALITY Absent- Atrial Fibrillation -Atrial Flutter -Ventricular Tachycardia -SVT -Hyperkalaemia Single for every QRS complex Tall/Peaked-Right Atrial Hypertrophy/Enlargement Wide/Broad/Notched-LA Hypertrophy/Enlargement Multiple-AV Block(Either Partial Or Complete)

Q WAVE ABNORMALITY Pathological Q wave- Old MI - LVH - LBBB -Cardiomyopathy -Emphysema(due to axis change) -Pulmonary Embolism(lead III)

R WAVE ABNORMALITY Tall- LVH(in V5/V6) - RVH(in V1/V2) - True Posterior MI Small-Obesity -Emphysema -Pericardial Effusion -Hypothyroidism -Hypothermia Poor Progression of R wave-COPD -PE(left) -Pneumothorax (left) -Cardiomyopathy -Ant/Anteroseptal MI

QRS COMPLEX ABNORMALITY High Voltage-Thin Chest Wall, Ventricular Hypertrophy Low Voltage-Thick Chest wall, Hypothyroidism, Pericardial Effu-

sion, Emphysema, Hypothermia, Chronic constrictive Pericarditis Wide QRS-BBB -Ventricular Ectopic -VT -Ventricular Enlargement -Hyperkalaemia Narrow QRS-SVT

T WAVE ABNORMALITY Inversion-MI, Ventricular ectopic, Ventricular Hypertro-

phy with strain, Cardiomyopathy, Acute Pericarditis, BBB Tall Peaked-Hyperkalaemia, Hyper acute MI, Acute True

Post. MI Small- Hypokalaemia, Hypothyroidism, Pericardial Effu-

sion

U WAVE ABNORMALITY Inversion- Ischemic Heart Disease -LVH with strain Prominent-Hypokalaemia -Hypercalcemia -Hyperthyroidism

PR INTERVAL ABNORMALITY Prolonged- First Degree Heart Block(Causes- IHD, Acute

Rheumatic Carditis, Myocarditis, Hypokalaemia, Atrial Dilata-tion or Hypertrophy)

Short- WPW syndrome Variable-Second Degree Block( Type I and Type II) -Third Degree Block

ABNORMALITY OF ST SEGMENT

ST ELEVATION PATTERN

PROLONGED QTC (ABCDE) AntiArrythmic-Amiodarone,Flecainide,Disopyramide AntiBiotic-Macrolides AntiC(Psy)cotic-Chlorpromazine, Haloperidol AntiDepressant-TCAEI-Hypokalaemia, Hypomagnaesemia, Hypocalcemia

SHORTENED QT Digitalis effect Hypercalcemia Hyperthermia Vagal stimulation

ARRHYTHMIA & ECG

SINUS BRADYCARDIA

SINUS TACHYCARDIA

HEART BLOCK SA Block

AV Block -1st degree AV block -2nd degree AV block( Type I & Type II) -3rd degree AV block

BBB -RBBB -LBBB

SA BLOCK

Absence of one P-QRS-T complex Pause is multiple of P-P interval(or R-R interval)

IMPORTANT DIFFERENTIAL IS SA AR-REST…

Absence of one P-QRS-T complex Pause is NOT multiple of P-P interval(or R-R interval)

AV BLOCK

RBBB

LBBB

ATRIAL FIBRILLATION

ATRIAL FLUTTER

ATRIAL TACHYCARDIA/SVT

ATRIAL ECTOPIC/PAC

JUNCTIONAL ECTOPIC/PJC

VENTRICULAR ECTOPIC/PVC

MI & ECG

CHANGE IN INJURY, ISCHEMIA & INFARC-TION

RECIPROCAL LEADS

LATERAL MI

ANTEROSEPTAL MI

EXTENSIVE ANTERIOR MI

INFERIOR MI

POSTERIOR MI

ST depression in V2-V3 Tall, Broad R wave in V2-V3 Dominant R wave in V2(R>S) Upright T wave

Posterior MI confirmed by posterior lead V7, V8, V9V7=Left Post. Axillary line, same plane to V6V8=Tip of the scapulaV9=Left Paraspinal line

Same case with posterior leadST segment elevation in V7-V9

DIFFERENCE BETWEEN MI AND ACUTE PERICARDITIS

ST shape-Convex Up Location of ST change-

Territorial Reciprocal ST change-

Present Q wave change-May be

Present

ST shape-Concave up Location of ST change-

Limb & Precordial Reciprocal ST change-Ab-

sent Q wave change-Absent

Acute MI Acute Pericarditis

EI & ECG

HYPOKALEMIA

HYPERKALEMIA

HYPOCALCAEMIA & HYPERCAL-CEMIA

THYROID DISORDER & ECG

HYPOTHYROIDISM

HYPERTHYROIDISM/ THYROTOXICOSIS

EMERGENCY ECG

VENTRICULAR TACHYCARDIA

VENTRICULAR FIBRILLATION

ASYSTOLE

THANK YOU….