normalecginterpretation in human heart ppt

Evaluation of normal ecg

1. Normal ECG Interpretation

2. INTRODUCTION The electrocardiogram (ECG) is one of the simplest and oldest cardiac investigations available, yet it can provide a wealth of useful information and remains an essential part of the assessment of cardiac patients. With modern machines, surface ECGs are quick and easy to obtain at the bedside and are based on relatively simple electrophysiological concepts.

3. What is an ECG? An ECG is simply a representation of the electrical activity of the heart muscle as it changes with time, usually printed on paper for easier analysis. Like other muscles, cardiac muscle contracts in response to electrical depolarization of the muscle cells. It is the sum of this electrical activity, when amplified and recorded for just a few seconds that we know as an ECG.

4. Recording the EKG Basics: ECG graph: 1 mm small squares 5 mm large squares Paper speed 25 mm/sec standard

5. The vertical lines measure amplitude or voltage Each small box represents 0.1 Mv Each l a rge b l o c k (m a de u p o f 5 sm a ll boxes) represents 0.5 mV The horizontal lines measure time Each small box equals 0.04 seconds 2 . Each l a r g e b l o c k (m a de u p o f 5 small b o x e s ) equals 0.2 seconds (multiply 0.04 x 5 = 0.2)

6. Major waves of a single normal ECG pattern P wa v e : R e presents Atrial depolarization , initiated by the SA node. Characteristics: 1.width <3 small squares (0.12 sec) and height <2.5 mm 2 . Upward i n l e a ds I,I I an d i n vert ed i n lead a V R . This is called sinus’ P’ wave. 3 .P w a ve aft er the Q RS Co mp le x ( R e t r og r ade P w a v e) or inverted P wave indicates its origin from other source.

7. QRS complex It Represents ventricle depolarization This also happens to coincide with the part of the cardiac cycle when the myocardial cells in the atria are repolarizing. The impulse is slightly delayed at the AV node before entering the ventricles through the Common AV Bundle .

8. Characteristics Completely negative in lead aVR, maximum positivity in lead II Normal duration between 0.08 and 0.10 sec, not more than 0.12 sec. Physiological Q wave not >0.03 sec. In a right ventricular lead (V1) the S wave is greater than the R wave the height of the R wave in the left ventricular leads (V5, V6) is less than 25 mm

9. Normal QRS V1 V6

10. J -p o int Is the end of the QRS complex and the beginning of the ST segment.

11. Normal T wave eads and <10 mm in It Represents Re polarization of ventricles . Same direction as the preceding QRS complex Height <5mm in limb l precordial leads Smooth contours May be tall in athletes

12. The normal U Wave It represents re polarization of purkinje fibers and/or the ventricular septum . The most neglected of the ECG waveforms U wave amplitude is usually < 1/3 T wave amplitude in same lead. U wave direction is the same as T wave direction in that lead. U waves are more prominent at slow heart rates and usually best seen in the right precordial leads.

13. Intervals and segments PR Interval: From the start of the P wave to the start of the QRS complex PR Segment : From the end of the P wave to the start of the QRS complex J Point: The junction between the QRS complex and the ST segment QT Interval: From the start of the QRS complex to the end of the T wave QRS Interval: From the start to the end of the QRS complex ST Segment: From the end of the QRS complex (J point) to the start of the T wave

14. Intervals and segments

15. Normal intervals PR interval: (measured from the beginning of the P wave to the first deflection of the QRS complex). Normally lasts 0.12 and 0.20 seconds. (3 – 5 small squares on ECG paper). QRS Interval: (measured from first deflection of QRS complex to end of QRS complex at isoelectric line). Interval usually lasts between 0.08 and 0.12 seconds. (3 small squares on ECG paper ).

16. R-R interval - The RR interval represents the amount of time between heart beats. Thus, the RR interval is heart rate dependent .

17. QT interval (measured from first deflection of QRS complex to end of T wave at isoelectric line). it is usually about 0.35 seconds in duration, but the duration of the QT interval is very heart rate dependent. ST segment - Is the segment between the J point (the end of the QRS complex) and the beginning of the T wave.

18. ECG Interpretation What is your approach to reading an ECG? Rate Rhythm Axis Wave morpholo Intervals and Segment analys gy is

19. The rule of 300 No of big Rate (apprx) boxes 1 300 2 150 3 100 4 75 5 60 6 50

20. 10 second rule As most ECG record 10 seconds of rhythm per page, one can simply count the number of beats present on the ECG and multiply by 6 to get the number of beats per seconds. Rate : (Number of waves in 10 second strips)x6 This method works well for irregular rhythm

21. Count QRS in 10 second rhythm strip x 6  use this method to determine rate when rhythm is irregular (e.g., atrial fibrillation)

22. Rhythm Look at the rhythm strip below and answer the questions Are P waves present? yes Is there a P wave before every QRS complex and a QRS complex after every P wave? y e s y e s Is the PR interval constant? yes  Yes to all these Are the P waves and QRS complexes regular ? questions, so this is normal sinus rhythm !

23. Normal Sinus Rhythm ECG rhythm characterized by a usual rate of anywhere between 60 and 100 beats per min. Every P wave must be followed by a QRS And every QRS is preceded by P wave. Normal duration of PR interval is 3-5 small squares The P wave is upright in leads I and II.

24. Axis Axis i s t he g e n e ral fl o w o f elect r icity a s it passes through the heart T h e QR S axis r e p res en ts th e n et over a ll direction of the heart’s electrical activity.

25. To determine cardiac axis look at QRS complexes of lead II ,III. AXIS LEAD II LEADIII Normal Positive P o sitive/ne g ativ e Right axis deviation Positive Positive Left axis dev i ation Negative Negative

26. Normal R Wave Progression Transition Zone?

27. Normal ECG