How to read ECG

( The Second Edition ） 23rd March 2020

CONTENTS • 1.Understanding Electrocardiogram………………………………………………………………………………………………………3

• 2.ECG Parameter……………………………………………………………………………………………………………………………….….4

• 3.RR Wave……………………………………………………………………………………………………………………………………..……..5

• 4.PR Interval……………………………………………………………………………………………………………………………………..…..6

• 5.QRS complex……………………………………………………………………………………………………………………………………...7

• 6.ST Segment…………………………………………………………………………………………………………………………………………8

• 7.T wave…………………………………………………………………………………………………………………………………………….….9

• 8.QT Interval……………………………………………………………………………………………………………………………………….10

• 9.Typical Patterns………………………………………………………………………………………………………………………………..11

• 10.Premature Contractions………………………………………………………………………………………………………………….12

• 11.Summary………………………………………………………………………………………………………………………………………..12

• 12.Reference……………………………………………………………………………………………………………………………………….13

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1.Understanding Electrocardiogram

ECG Axis -Vertical axis measurement unit : mv -Horizontal axis measurement unit: s -Width of 1 small square : 0.04s -Width of 5 small squares: 0.2s -Width of 2 large squares : 1 mv -Wave height measurement unit: mm, width of each small square 1mm

Gain : 10mm/mV， Speed：25mm/s

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2.ECG Parameter Parameter Reference Range

Average Heart Rhythm (HR) 60 ~100 bpm (static state)

RR Wave 0.6 s ~ 1.2S (15 to 25 small squares)

P Wave

Width<0.12s (less than 3 small squares) Amplitude < 0.25mV (less than 2.5 small squares)

PR Interval 0.12s ~ 0.20 s (3 to 5 small squares)

QRS Complex (QRS) 0.08s ~0.12 s (2 to 3 small squares)

ST Segment (ST) 0.08s ~ 0.12s (2 to 3 small squares)

T Wave

Width 0.1s ~ 0.25s (2.5 to 6.5 small squares) Amplitude (Man) : 6~10mm (6-10 small squares) (Woman) : 3~8mm (3-8 small squares)

QT 0.3s ~ 0.46 s (7.5 to 11.5 small squares)

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3.RR Wave

• Normal range: 0.6s ~1.2s (15 – 25 small squares) • Reference diagnostic: The width of RR reflects individual average heartbeat, which is measured by 1 minute per heartbeats, adult

normal resting heart rate between 60 – 100 beats per minute.

P Wave

-Normal range < 0.12s (less than 3 small squares), amplitude < 0.25mV (less than 2.5 small squares) -Reference diagnostic: P wave refers to atrial activity, if P wave does not exist and the heart rhythm is irregular, it indicates atrial fibrillation.

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4.PR Interval • Normal range: 0.12s ~ 0.2s (3-5 small squares) • Reference diagnostic: PR interval describes atrioventricular conducting system. Prolonged PR interval(＞0.2s): 1st First degree & 2nd degree AV block（Mobitz I & II）

Shortened PR interval (＜0.12s): Wolff Parkinson White syndrome

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5.QRS complex

• Normal range: 0.08s ~ 0.12s (2-3 small squares) • Reference diagnostic: QRS complex is composed of Q wave, R wave & S wave, all waves do not

necessarily exist at the same time, but collectively called QRS complex. Any unusually QRS complex can be diagnosis as arrhythmia, ventricular

hypertrophy, acute STEMI, ventricular premature beat, hyperkalaemia, pre-excitation syndrome, bundle branch block, electrolyte abnormalities, and antiarrhythmic drugs effect.

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6.ST Segment

• Normal range: 0.08s ~ 0.12s (2-3 small squares) • Reference diagnosis: ST segment is the flat and isoelectric section between the

end of the QRS wave and beginning of the T wave. ST elevation: acute STEMI, variant angina pectoris, ventricular aneurysm, Brugada. ST depression: myocardial ischemia, heart failure, ventricular hypertrophy etc. Prolonged: hypocalcemia, coronary heart disease etc. Shortened: hypercalcemia, Digoxin effect etc.

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7.T wave • Normal range: Width 0.1s ~ 0.25s (2.5 – 6 small squares) Amplitude 6 ~ 10mm (Man) / 3 ~ 8mm (Woman) • Reference diagnosis: Tall - hyperkalaemia & hyperacute STEMI. Inverted - ischaemia , bundle branch blocks, pulmonary embolism, left ventricular

hypertrophy , hypertrophic cardiomyopathy. Biphasic - ischaemia and hypokalaemia. Fattened - ischaemia or electrolyte imbalance.

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8.QT Interval

• Normal range: 0.3s-0.46s (7.5 - 11.5 small squares) • Reference diagnosis: Abnormal syndrome reflects drug effect and electrolyte

abnormalties. • Prolonged QT is one of the risk factors for ventricular tachycardia and may cause

sudden death. An unusually short QTc can be seen in severe hypercalcemia.

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9.Typical Patterns

PVC Bigeminy

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10.Premature Contractions Item(s) Premature Ventricular Complex (PVC) Premature Atrial Complex (PAC) Premature Junctional Complex (PJC)

Definition Premature beats within ventricle Premature beats within atrium premature cardiac electrical impulses

arising from the AV node of the heart or "junction".

Heart Rhythm Irregular Irregular Irregular

Heart Rate Irregular while PVC occurs Normal usually, abnormal while PAC occurs Irregular while PJC occurs

P Wave Absent Abnormal Absent, inverted, hidden or present before

PR Interval Not related with PVC Normal or prolonged (>0.12s) Absent, short or present before (<0.12s)

QRS Wide (＞0.12s), abnormal morphology,

ST segment & T wave is directed opposite to the direction of QRS complex

Normal (0.08 ~ 0.12s) Normal (0.08 ~ 0.12s)

Features Unifocal / multifocal, repeated QRS pattern

Couplet — two consecutive PVCs. Triplet — three consecutive PVCs.

Unifocal / multifocal, repeated P pattern Couplet — two consecutive PVCs. Triplet — three consecutive PVCs.

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Diagnostics Coronary heart disease, cardiomyopathy, rheumatic heart disease, such as myocardial ischemia

WPW, hypokalaemia, hypomagnesaemia, digoxin toxicity etc

11.Summary BISA ECG is only used for monitoring personal health daily, all data are for reference only. If user feels uncomfortable, should contact your doctor for medical treatment.

BISA Technologies (Hong Kong) Limited FLAT/RM 315, Trans Asia Centre, 18 Kin Hong Street, Kwai Chung, NT, Hong Kong

BISA Technologies (Shenzhen) Limited Unit 10E, Kechuang Building, Quanzhi Science & Technology Innovation Park, Hou Ting, Shajin Street, Baoan

District, Shenzhen, CHINA •Website: www.bisahealth.com Email: bisapecg@bias.com.hk

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Reference Links 1. Life in the Fastlane https://litfl.com/premature-atrial-complex-pac/ 2. Life in the Fastland https://litfl.com/premature-ventricular-complex-pvc-ecg-library/ 3. Practical Clinic Skill (EKG Reference Guide) https://www.practicalclinicalskills.com/ekg-reference 4. "簡易心電圖判讀 - 彰化基督教醫院" 5. 基本心電圖圖例簡介 - 達楷生醫科技股份有限公司

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