ECG in IHD

Topics will be covered• ECG basics• How to identify normal ECG• How to identify abnormal findings in ECG

– Atrial hypertrophy - Hyperkalaemia– Atrial fibrillation - Hypokalaemia– Atrial flutter- Pericarditis– Heart blocks– Chambers enlargement– IHD– AMI

Topics will not be covered• Signs and symptoms of the diseases with

abnormal ECG • Treatments of those diseases

What is ECG?• ECG is a medical device capable of

recording the electrical activity of the heart from electrodes placed on the skin in specific locations.

Standard ECG leads• Limb leads

Bipolar limb leads – I, II, IIIUnipolar limb leads – aVL, aVR, aVF

• Chest leadsV1 - V6

Right Arm

Right Leg

Left Leg

Left Arm

• Limb leads are typically placed on the inside of the wrists and ankles

• To help reduce artifacts you can use the upper arms and thighs

• Do not place limb leads on the torso

Limb leads

Chest Leads look at the heart in Chest Leads look at the heart in a horizontal plane.a horizontal plane.

• V1: right sternal edge (4th)V1: right sternal edge (4th)• V2: Left sternal edge (4th)V2: Left sternal edge (4th)• V4: the patient’s apex V4: the patient’s apex

beatbeat• V3: half-way b/t V2 and V4V3: half-way b/t V2 and V4• V5: anterior axillary lineV5: anterior axillary line• V6: mid-axillary lineV6: mid-axillary lineV5 and V6 are in the same V5 and V6 are in the same

horizontal plane as V4horizontal plane as V4ChestLeads

Interpretation of an ECGPatient identificationStandardization1.Rate2.Rhythm3.Axis4.P wave5.PR interval6.QRS complex7.ST segment8.T wave9.U wave10.QT interval

Conduction system of heart

Wave. Interval. Complex.• One letter = wave

– Eg = P, T• Need to check height and width

• Two letters = interval– PR interval

• Need to check length

• 3 letters = complex– QRS complex

• Need to check height, width and shape

• Name• Age • ID number• DOB• Father’s name

Patient identification and standardization

• Regular RhythmRate = 300÷numbers of large square

• Irregular RhythmNumbers of R in 6 sec x 10 (6s method)

Rate determination

Regular Rhythm

Irregular Rhythm

Using 6-sec ECG rhythm strip to calculate heart rate: 7×10 = 70 bpm.

P wave• Atrial depolarization• Best seen at Lead II• Normal Height <2 ⅟2 small square Width <2 ⅟2 small square

Causes of ST depression• Angina

• NSTEMI

• LVH

ST depression

• A – upward may be normal• B – down sloping strain / digoxin effect• C – planar ischaemia***

Angina Pectoris• Imbalance between myocardial oxygen

demand and supply• ST depression and/or T inversion

Causes of ST elevation

• AMI

• Pericarditis

Acute Myocardial Infarction• Hyper acute T • ST elevation – myocardial injury• T inversion – myocardial injury• Q wave – myocardial necrosis

Q wave• NormalLateral leads (I,aVL,V5,V6)III alone mb present1:1:4 =Physiological Q(height <1 ssq, width < 1ssq,Q <1/4 R)

-Old MI

Standard ECG leads• Limb leads

Bipolar limb leads – I, II, IIIUnipolar limb leads – aVL, aVR, aVF

• Chest leadsV1 - V6

Infarction Leads

Inferior II,III,aVF

Lateral I,aVL,V5,V6

Septal V1,V2

Anterior V1-V4

Localizing the Infarct

Inferior Infarction

• Right coronary artery

• Leads II, III, aVF

Inferior Infarction

I II III aVR aVL aVF V1 V2 V3 V4 V5 V6

Right coronary artery

Lateral Infarction

• Left circumflex artery

• I, aVL, V5, V6

• Usually associated with another infarction

Lateral Infarction

I II III aVR aVL aVF V1 V2 V3 V4 V5 V6

Left circumflex artery

Anterior Infarction

• Left anterior descending artery

• V2-V4

• V1-V4 = antero-septal infarction

• V1-V6 = extensive anterior infarction

Anterior Infarction

I II III aVR aVL aVF V1 V2 V3 V4 V5 V6

LADA

Pericarditis

T wave• Normal1/8 R < T < 2/3 R

• Tall T– Peak T wave (> 50% of preceding R)– Hyperkalaemia(Tall T , Small P, Wide QRS)

U wave• Slow repolarization of papillary muscle

• Normal – V1, V2

• Prominent U wave – hypokalaemia

Interpretation of an ECGPatient identificationStandardization1.Rate2.Rhythm3.Axis4.P wave5.PR interval6.QRS complex7.ST segment8.T wave9.U wave10.QT interval

P wave : Duration: 0.08 sec ( 2 small squares ) Height: < 2.5 mm ( 2 small squares )

PR interval: Duration: 0.12 - 0.20 sec (3-5 small squares)

QRS Complex : Duration: 0.07–0.10 sec(2 – 2½ small squares)

ST segment : Isoelectric

T wave : 1/8 previous R < T < 2/3 previous R

Important intervals and durations

Thank You