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Introduction to ECG EEE 491 Biomedical Engineering Compiled by Dr. Khawza I Ahmed.

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Presentation on theme: "Introduction to ECG EEE 491 Biomedical Engineering Compiled by Dr. Khawza I Ahmed."— Presentation transcript:

1 Introduction to ECG EEE 491 Biomedical Engineering Compiled by Dr. Khawza I Ahmed

2 What is ECG? The electrocardiogram (ECG) is a time-varying signal reflecting the ionic current flow which causes the cardiac fibers to contract and subsequently relax. The surface ECG is obtained by recording the potential difference between two electrodes placed on the surface of the skin. A single normal cycle of the ECG represents the successive atrial depolarisation/repolarisation and ventricular depolarisation/repolarisation which occurs with every heart beat. The electrocardiogram (ECG) is a time-varying signal reflecting the ionic current flow which causes the cardiac fibers to contract and subsequently relax. The surface ECG is obtained by recording the potential difference between two electrodes placed on the surface of the skin. A single normal cycle of the ECG represents the successive atrial depolarisation/repolarisation and ventricular depolarisation/repolarisation which occurs with every heart beat. Simply put, the ECG (EKG) is a device that measures and records the electrical activity of the heart from electrodes placed on the skin in specific locations Simply put, the ECG (EKG) is a device that measures and records the electrical activity of the heart from electrodes placed on the skin in specific locations

3 What the ECG is used for? Screening test for coronary artery disease, cardiomyopathies, left ventricular hypertrophy Screening test for coronary artery disease, cardiomyopathies, left ventricular hypertrophy Preoperatively to rule out coronary artery disease Preoperatively to rule out coronary artery disease Can provide information in the precence of metabolic alterations such has hyper/hypo calcemia/kalemia etc. Can provide information in the precence of metabolic alterations such has hyper/hypo calcemia/kalemia etc. With known heart disease, monitor progression of the disease With known heart disease, monitor progression of the disease Discovery of heart disease; infarction, coronal insufficiency as well as myocardial, valvular and cognitial heart disease Discovery of heart disease; infarction, coronal insufficiency as well as myocardial, valvular and cognitial heart disease Evaluation of ryhthm disorders Evaluation of ryhthm disorders All in all, it is the basic cardiologic test and is widely applied in patients with suspected or known heart disease All in all, it is the basic cardiologic test and is widely applied in patients with suspected or known heart disease

4 Measuring ECG ECG commonly measured via 12 specifically placed leads ECG commonly measured via 12 specifically placed leads

5 For more presentations www.medicalppt.blogspot.com The 12-Leads The 12-leads include: –3 Limb leads (I, II, III) –3 Augmented leads (aVR, aVL, aVF) –6 Precordial leads (V 1 - V 6 )

6 Typical ECG A typical ECG period consists of P,Q,R,S,T and U waves A typical ECG period consists of P,Q,R,S,T and U waves

7 ECG Intervals / Segments PR: 0.12-0.20 sec QRS: <0.10 sec QT: 0.30-0.40 sec (60 bpm)

8 ECG Waves P wave: the sequential activation (depolarization) of the right and left atria P wave: the sequential activation (depolarization) of the right and left atria QRS comples: right and left ventricular depolarization QRS comples: right and left ventricular depolarization T wave: ventricular repolarization T wave: ventricular repolarization U wave: origin not clear, probablyafterdepolarizations in the ventrices U wave: origin not clear, probablyafterdepolarizations in the ventrices

9 ECG Example

10 ECG Signal Generation

11 Action Potential

12 Electrocardiogram (ECG/EKG) Is a recording of electrical activity of heart conducted thru ions in body to surface Is a recording of electrical activity of heart conducted thru ions in body to surface 13-60

13 Cardiac Cellular Electrical Activity Typical Equilibrium Potentials: Na(+) ~+40mV K(+) ~-90mV C(++) ~+150mV

14 ECG recording

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19 3 distinct waves are produced during cardiac cycle 3 distinct waves are produced during cardiac cycle P wave caused by atrial depolarization P wave caused by atrial depolarization QRS complex caused by ventricular depolarization QRS complex caused by ventricular depolarization T wave results from ventricular repolarization T wave results from ventricular repolarization ECG Fig 13.24 13-63

20 Elements of the ECG: P wave: Depolarization of both atria; Relationship between P and QRS helps distinguish various cardiac arrhythmias Shape and duration of P may indicate atrial enlargement PR interval: from onset of P wave to onset of QRS Normal duration = 0.12-2.0 sec (120-200 ms) (3-4 horizontal boxes) Represents atria to ventricular conduction time (through His bundle) Prolonged PR interval may indicate a 1st degree heart block QRS complex: Ventricular depolarization Larger than P wave because of greater muscle mass of ventricles Normal duration = 0.08-0.12 seconds Its duration, amplitude, and morphology are useful in diagnosing cardiac arrhythmias, ventricular hypertrophy, MI, electrolyte derangement, etc. Q wave greater than 1/3 the height of the R wave, greater than 0.04 sec are abnormal and may represent MI

21 ST segment: Connects the QRS complex and T wave Duration of 0.08-0.12 sec (80-120 msec T wave: Represents repolarization or recovery of ventricles Interval from beginning of QRS to apex of T is referred to as the absolute refractory period QT Interval Measured from beginning of QRS to the end of the T wave Normal QT is usually about 0.40 sec QT interval varies based on heart rate

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23 Fig. 13.24b

24 Fig. 13.24c

25 Fig. 13.24d

26 Elements of the ECG: P wave Depolarization of both atria; Relationship between P and QRS helps distinguish various cardiac arrhythmias Shape and duration of P may indicate atrial enlargement

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28 QRS complex: Represents ventricular depolarization Larger than P wave because of greater muscle mass of ventricles Normal duration = 0.08-0.12 seconds Its duration, amplitude, and morphology are useful in diagnosing cardiac arrhythmias, ventricular hypertrophy, MI, electrolyte derangement, etc. Q wave greater than 1/3 the height of the R wave, greater than 0.04 sec are abnormal and may represent MI

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30 PR interval: From onset of P wave to onset of QRS Normal duration = 0.12-2.0 sec (120-200 ms) (3-4 horizontal boxes) Represents atria to ventricular conduction time (through His bundle) Prolonged PR interval may indicate a 1st degree heart block

31 Fig. 13.24g

32 T wave: Represents repolarization or recovery of ventricles Interval from beginning of QRS to apex of T is referred to as the absolute refractory period

33 ST segment: Connects the QRS complex and T wave Duration of 0.08-0.12 sec (80-120 msec QT Interval Measured from beginning of QRS to the end of the T wave Normal QT is usually about 0.40 sec QT interval varies based on heart rate

34 ECG recording

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