Electrocardiograph analysis

1. Reported by: AGNES Purwidyantri BIOMEDICAL ENGINEERING DEPT Electrocardiographanalysis

2. ECG interpretation - step-by-step • Rate • Rhythm • Cardiac Axis • P – wave • PR - interval • QRS Complex • ST Segment • QT interval (T & U wave) • Other ECG signs

3. ELEMENTS OF ECG Cardiac Electrophysiology Pacemakers of Heart • Electrical activity is governed by multiple transmembrane ion conductance changes • 3 types of cardiac cells • 1. Pacemaker cells- SA node, AV node • 2. Specialised conducting tissue – (Purkinjee Fibers) • 3. Cardiac myocytes • SA Node - Dominant pacemaker -intrinsic rate of 60 - 100 beats/minute. • AV Node - 40 - 60 beats/minute. • Ventricularcells- 20 - 45 beats/minute.

5. The Normal Conduction System

6. Electrocardiogram • Is a recording of electrical activity of heart conducted through ions in body to surface 13-60

7. EKG Distributions • Anteroseptal: V1, V2, V3, V4 • Anterior: V1–V4 • Anterolateral: V4–V6, I, aVL • Lateral: I and aVL • Inferior: II, III, and aVF • Inferolateral: II, III, aVF, and V5 and V6

8. Rate • HR of 60-100 per minute is normal • HR > 100 = tachycardia • HR < 60 = bradycardia • Rule of 300- Divide 300 by the number of boxes between each QRS = rate

9. Differential Diagnosis of Tachycardia

10. What is the heart rate? www.uptodate.com (300 / 6) = 50 bpm

11. Rhythm • Sinus • Originating from SA node • P wave before every QRS • P wave in same direction as QRS

12. What is this rhythm? Normal sinus rhythm

13. Normal Intervals • PR • 0.20 sec (less than one large box) • QRS • 0.08 – 0.10 sec (1-2 small boxes) • QT • 450 ms in men, 460 ms in women • Based on sex / heart rate • Half the R-R interval with normal HR

15. Waveforms & Intervals

16. P Wave • Depolarization of both atria • Relationship b/w P & QRS - distinguish various arrhythmias • Shape & duration of P - indicate atrial enlargement

17. PR INTERVAL • Onset of P wave to onset of QRS • Normal = 0.12 - 2.0 sec • Represents A to V conduction time (via His bundle) • Prolonged PR interval indicate AV block

18. Short PR Interval WPW Sx Accessory pathway (Bundle of Kent) - early activation of the ventricle (delta wave & short PR interval)

19. Long PR Interval • 1st degree Heart Block

20. Ventricular Depolarization Includes • Bundle of His • Bundle Branches • Right • Left • Septal • Anterior • Posterior • Terminal Purkinjie fibers

21. What is the axis? Normal- QRS up in I and aVF

22. Hypertrophy • Add the larger S wave of V1 or V2 in mm, to the larger R wave of V5 or V6. • Sum is > 35mm = LVH

23. Ischemia • Usually indicated by ST changes • Elevation = Acute infarction • Depression = Ischemia • Can manifest as T wave changes • Remote ischemia shown by q waves

24. Lead Placement aVF

25. All Limb Leads

26. Precordial Leads

27. QRS COMPLEX • Ventricular depolarization • Is > P wave d/t > Ventricular mass • Normal duration = 0.08 - 0.12 secs • Q wave >1/3 the height of R wave, >0.04 sec –abnormal; may represent MI

28. ST Segment • Connects QRS complex & T wave • Duration = 0.08 - 0.12 sec

29. T Wave • “small to moderate” size +ve deflection wave after QRS complex, • Ht is 1/3rd - 2/3rd that of corresponding R wave • Septal repolarization (not always seen on ECG) U Wave

30. QT Interval • Beginning of QRS to end of T wave • Normal QT is usually about 0.40 sec • QT varies based on HR- faster HR ,shorter QT . • Hence QTc. • Bazett’s formula: QTC = QT / √ RR • Fredericia’s formula: QTC = QT / RR 1/3 • Framingham formula: QTC = QT + 0.154 (1 – RR) • Hodges formula: QTC = QT + 1.75 (HR– 60)

31. CALCULATING RATE Eg 1500 300 Rate = or Rate = 15 3 Rate = 100 beats/minute

32. CALCULATING RATE Rhythm irregular- # of beats in a 6-sec X by 10 1 2 3 4 5 6 7 8 There are 8 waves in this 6-seconds strip. = (Number of waves in 6-sec strips) x 10 = 8 x 10 = 80 bpm Rate

33. References • The EKG made easy-John R. Hampton • An Introduction to Electrocardiography – Leo Schamroth • Marriot’s Practical Electrocardiography. • www.ambulancetechnicianstudy.co.uk • www.learntheheart.com