Understanding basics of EKG

Transcription

1 Understanding basics of EKG By Alula A.(R III)

2 Topic for discussion Understanding of cellular electrophysiology Basics Rate Rhythm Axis Intervals P wave QRS ST/T wave Abnormal EKGs

3 Understanding electrophysiology The EKG is nothing more than a recording of the heart's electrical activity

4 Cardiac cells Resting state(mme pump) Depolarization /Repolarization

5 The Cells of the Heart and action potential

6 EKG basics

7 Electrode placement Right precordial leads V1: right 4 th intercostal space V2: left 4 th intercostal space V3: halfway between V2 and V4 Left Precordial leads V4: left 5 th intercostal space, MCL V5: horizontal to V4, anterior axillary V6: horizontal to V5, mid-axillary line

8 Limb leads

9 EKG grid The wave on EKG primarily reflect the electrical activity of myocardial cell Three chief characteristics of the waves. Duration Amplitude Configuration

10 EKG strip

11 Einthoven's Triangle

12 The Six Precordial Leads Record forces moving anteriorly and posteriorly 12

13 Order of depolarization

14 Follow the way

15 Interpretation steps RRAI- P-QRS-T Rate Rhythm Axis Intervals P wave QRS T

16 Rate Atrial/ Ventricular rate bpm Regular RR; 1500/small box or 300/large box Irregular RR # of QRS waves in 6 sec X 10 # of QRS on the whole EKG(10 Sec) X6

17 Rhythm Normal sinus Rhythm( originated from SA) The P waves in leads I and II upright Same morphology before each QRS Read on the rhythm strip at lead II if not V1

18 Axis Two technique; I. Identification of isoelectric lead or II. Look for lead I and avf If needed look for lead II QRS axis Frontal Plane QRS Axis: +90 o to -30 o (in the adult)

19 Normal Axis

20 Left axis lead I +ve and avf -ve Look lead II +ve = normal axis -ve = left axis deviation - LA fascicular block - Inferior MI - Pacemaker

21 Right axis lead I - ve and avf +ve - RVH - Left posterior fascicular block - PE

22 Intervals PR interval Normal sec QT interval QT c < 0.40 sec Bazett's Formula: QT c = (QT)/SqRoot RR (in seconds)

23 P wave Bi atrial activation Right to left Lead II or V1 - duration < 0.12 sec - 3 blocks wide - amplitude < 2.5 mm 2.5 blocks high

24 P wave Normal Up in lead II Down in avr Biphasic, up or down in V1, III Same morphology and PR before each QRS Abnormal too wide, too tall, different, unclear, funny (i.e. LAE, RAE, wandering pacemaker/mat, a fib respectfully)

25 Wandering Pacemaker at least 3 different P wave morphologies in a Ventricular response is irregularly irregular, COPD

26 QRS Duration < 0.10 sec QRS amplitude - variable from lead to lead and from person to person Comment: pathologic Q waves, abnormal voltage

27 QRS Q wave Narrow (<0.04s duration) and Small (<25% the amplitude of the R wave) 0.1mv Often seen in leads I and avl when the QRS axis is to the left of +60 o, and leads II, III, avf when the QRS axis is to the right of +60 o. R-waves begin in V1 or V2 and progress in size to V5. R-V6 < R-V5. In reverse, the S-waves begin in V6 or V5 and progress in size to V2. S- V1 is usually smaller than S-V2 The usual transition from S>R in the right precordial leads to R>S in the left precordial leads is V3 or V4

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29 ST wave Normal V1-V3 concave upwards

30 ST / ST- T wave Abnormal ST elevation and/or Depression ST elevation **compare J point to the TP level not PR**

31 Early repolarization- concave upwards

32 ST elevation Convex or straight upward ST

33 ST segment depression abnormal but non specific

34 T wave The normal T wave is usually in the same direction as the QRS except in the right precordial leads( V1-V3) T wave amplitude is 1/3-2/3 of R wave Always upright in leads I, II, V3-6, and Always inverted in lead avr

35 U wave Afterdepolarizations which interrupt or follow repolarization 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 more prominent at slow heart rates and usually best seen in the right precordial leads

36 Conclusion ECG interpretations i. Measurements ii. Rhythm analysis iii. Conduction analysis iv. Waveform description v. ECG interpretation (normal, abnormal, bordeline) i. Comparison with previous ECG (if any) Remember RRAI P-QRS-T

37 Provided by The Leicester Gondar Link Collaborative Teaching Project This work is licensed under a Creative Commons Attribution-NonCommercial- NoDerivs 3.0 Unported License.