ecg made easy ecocadiograph interpretation

Ecocardiograph interpretation

1. EASY WAY TO UNDERSTAND ELECTROCARDIOGRAPH ( ECG OR EKG ) Daniel M.I. Alliangana , M.Phil. Department of medical Physiology School of Medicine College of Health Sciences Moi University

2. His restrictive covenant was more restrictive than sweetheart had originally thought. Comic Relief Hope you will read your ECG more carefully and understand than the medical student read bitterheart’s Easter Card message. OUT THE DOCTOR IS

3. EINTHOVEN In the late 1800' s and the early 1900's , a man named Willem Einthoven pioneered the practice of electrocardiography.  He developed a machine that was sensitive enough to reliably measure electrical differences between two different parts of the body.  Plotting the values measured over time gave a picture of the electrical activity of the human heart .

4. WHAT IS ECG( EKG ) ? IS the Instrument that records the electrical activity of the heart (measures electrical potentials on the body surface) It generates a record of the electrical currents associated with heart muscle activity MAIN USE - detection and diagnosis of heart abnormalities Electrocardiograph is the instrument Electrocardiogram is the record of that activity ( electrical activity of the heart on paper (chart).

5. CONFUSSIUS ECGs can be very confusing, and there are dozens of different methods of interpretation. BEFORE YOU GET CONFUSED HOW ECG WORKS LET’S UNDERSTAND THE HEART’S CONDUCTION SYSTEM FIRST.

6. A FIRECRACKER REPRESENTING THE HEART'S ELECTRICAL SYSTEMT

7. THE CONDUCTION SYSTEM

8. CONDUCTION AND CONTRACTION FUNCTION Sinus (SA) node - conduction only Atria muscle - conduction and contraction Atrioventricular (AV) node - conduction only Bundle of His - conduction only Bundle branches - conduction only Purkinje fibers - conduction only Ventricular muscle - conduction and contraction

9. ELECTRIC PATHWAYS OF THE HEART From the sinus node, the electrical signal travels along the wall (through the muscle NOT BLOOD ) of the atria.  Electricity can freely flow from one atrium to the other.  It can also flow from one ventricle to the other.  It cannot, however, pass freely between the atria and ventricles ; the two sets of chambers are electrically insulated .   The pathway that connects the atria and the ventricles is the atrioventricular (AV) node    

10. ELECTRIC PATHWAYS OF THE HEART Starts in the sinus node Travels through the atria by (possibly) a combination of regular muscle cells and specialized conduction cells.  The impulse should cover the entire wall of the atria Travels through the AV node (specialized conduction cells) Travels through the AV bundle ( the bundle of His , specialized conduction cells) Splits between the left and right bundle branches (specialized conduction cells) Enters various Purkinje fibers (specialized conduction cells) Finally Reaches the ventricular muscle cells

11. VOLUME CONDUCTOR When cell membranes in the heart depolarize, voltages change and currents flow. A human can be regarded as a bag of salt water ( with very baaad attitude ), in other words, a volume conductor , Changes in potential are transmitted throughout the body, and can be measured .

12. HEART DEPOLARISATION When the heart depolarizes , it's convenient (and fairly accurate) to represent the electrical activity as a dipole --- a vector between two point charges. Remember that a vector has both a size (magnitude), and a direction

13. TWO CHAMBERED HEART The normal heart has electrically speaking, only two chambers , an atrial and a ventricular `chamber'. Propagation of electrical activity spreads freely within atria and ventricles , but communication between these two chambers is limited to the AV node. Everyone knows that the P wave corresponds to atrial depolarization , the QRS complex to ventricular depolarization, and the T wave to r epolarization of the ventricle.

14. MYOCARDIAL ACTIVITY In order to be able to record myocardial activity , the electrocardiograph needs to be able to detect tiny changes in potential on the body surface. These are signals that are often around 1mV, and may be smaller . In addition, we need some reference point to which we can relate the potential changes.

15. ELECTRICAL CARDIAC CYCLE SUMMARY

16. ECG PAPER Don’t look at the tracing you will get confused !!!!!!!!! Your focus should be on the ECG paper !

17. ECG PAPER

18. Heart Rate :- 1500 ---------------------------------- Number of small squares between R—R Interval Time :- 25mm per 1 second. 1mm = 1/25 second 1mm = 1 small square = 0.04 seconds Amplitude :- 10 Divisions = 10mm = 1mv Standard calibration 25 mm/s 0.1 mV/mm We use the number 1500 because there are 1500 small squares in a minute

19. ECG WAVES Each electrical stimulus takes the form of a wave and so patterns emerge made up of a number of connected waves. A standard ECG is printed at 25mm per second or 25 small squares per second In this way it is possible to calculate the duration of individual waves and their intervals. A normal ECG contains waves, intervals, segments, and one complex

20. ECG WAVES The direction in which the waves point - indicates whether electricity is moving towards or away from a particular lead. The general direction in which electricity - normally travels through the heart is a downward diagonal line from the right shoulder to the left lower abdomen. This is because - the electrical stimulus originates in the SA node ( upper right side of the heart ) - travels through the AV node and bundle of His , and finishes mainly in the left ventricle . (remember that there is more conduction in the left ventricle ). So different leads may have waves pointing in different directions

21. ECG WAVES Electrical impulse ( wave of depolarization moving towards the positive end of the electrode ) that travels towards the electrode produces an upright (“positive”) deflection relative to the isoelectric baseline Eg . lead V6 (mid-left axilla, 5th intercostal space ), will always see the electrical stimulus coming towards it and therefore the waves expressed in V6 for sinus rhythm , PQRST , will always be point upwards .

22. ECG WAVES Electrical impulse that travels away from the electrode produces a downward (“negative”) deflection relative to the isoelectric baseline Eg. Lead AVR (right shoulder/right arm/wrist) will always see the electrical stimulus travelling away from it, therefore the waves expressed in AVR for sinus rhythm , PQRST , will all point downwards.

23. The P wave Occurs when the SA node creates an action potential that depolarizes the atria. The P wave should be upright in lead II if the action potential is originating from the SA node. If this is so, the ECG is said to demonstrate a "normal sinus rhythm" abbreviated "NSR". As long as the atrial depolarization is able to spread through the AV node to the ventricles, each P wave should be followed by a QRS complex.

24. The QRS complex Comes after the P wave when the SA nodal action potential travels through the AV node to the ventricles to cause ventricular depolarization. The first downward deflection is called the Q wave. The first upward deflection is called the R wave. The second downward deflection is called the S wave.

25. The T wave Occurs after the QRS complex and is a result of ventricular repolarization. T waves should be upright in most leads ( except aVR and V1 ). T waves should be asymmetric in nature. The second portion of the T wave should have a steeper decline when compared to the incline of the first part of the T wave. If the T wave appears symmetric, cardiac pathology may be present.

26. The U wave It is possible to see another wave after the PQRST complex. This is known as a U wave . It is not very common and is easy to overlook . U waves are indicated by the arrows

27. An interval Is the distance between two specific ECG events. For example: PR Interval (PRI ): The time from the beginning of the P wave (atrial depolarization) to the beginning of the QRS complex (ventricular depolarization). A prolonged or shortened PR interval can indicate certain disease states.

28. QT interval The time from the beginning of the QRS complex ( ventricular depolarization ) to the end of the T wave ( ventricular repolarization ). QT interval prolongation can be very serious.

29. In practice, the Q-T interval is expressed as a "corrected Q-T (QTc)" by taking the Q-T interval and dividing it by the square root of the R-R interval . This allows an assessment of the Q-T interval that is independent of heart rate. Normal corrected Q-Tc intervals are less than 0.44 seconds .

30. ECG LEADS Leads are electrodes which measure the difference in electrical potential between either: 1. Two different points on the body ( bipolar leads ) 2. One point on the body and a virtual reference point with zero electrical potential, located in the center of the heart ( unipolar leads )

31. ELECTRODE PLACEMENT LIMB LEADS made up of 4 leads placed on the extremities: left and right wrist left and right ankle. The lead connected to the right ankle is a neutral lead , like you would find in an electric plug. It is there to complete an electrical circuit and plays no role in the ECG itself. Bipolar leads I II III Augment leads Avr Avl Avf

32. Einthoven’s triangle The 2 leads situated on the right and left wrist (or shoulders), AVR and AVL respectively, and the lead situated on the left ankle (or left lower abdomen ) AVf , make up a triangle , known as "Einthoven’s Triangle". Information gathered between these leads is known as "bipolar". It is represented on the ECG as 3 "bipolar" leads. information between AVr and AVl is known as lead l . Information between AVr and AVf is known as lead ll Information between AVl and AVf is known as lead lll

33. Types of ECG Recordings Bipolar leads record voltage between electrodes placed on wrists & legs (right leg is ground) Lead I records between right arm & left arm Lead II : right arm & left leg Lead III : left arm & left leg 13-61

34. CREATION OF THE 6 VERTICAL LEADS The three bipolar leads (I, II and III) are calculated from the differences between points on Eindhoven's triangle. This creates the 6 vertical leads:

35. AXIS The peculiar system used in electrocardiography is non-Cartesian, and rather arbitrary! We measure the direction of vectors in degrees. zero is indeed facing ` East', but +90 o is South , instead of North as it would be in a Cartesian system. You can work out that ± 180 o is 'West', and that minus 90 o is 'North'.

36. Standard Limb Leads

37. Augmented Limb Leads

38. All Limb Leads

39. AXIS We can talk about the `axis' of any ECG depolarization , but most people when talking about the 'axis' refer to the mean frontal plane QRS axis . There is a number of ways of determining this, but the following method has the merit of simplicity: 1. Estimate the overall deflection ( positive or negative , and how much) of the QRS in standard lead I ; 2. Do the same for AVF ; 3. Plot the vector on a system of axes , and estimate the angle, thus: Note in the above picture that the ( abnormal ) axis illustrated is negative ( "towards the left") because AVF is negative. (There are several other causes of left or right axis deviation , for example depolarization via accessory pathways

40. CHEST LEADS 6 UNIPOLAR LEADS V1,V2, V3,V4, V5, V6 The chest electrodes are labelled “V” and are numbered from 1 to 6.

41. The placement of these electrodes The placement of these electrodes needs to be exact to give the optimum information as possible. If the electrodes are placed incorrectly on the chest , the tracing will reveal duplication of some information , while other areas will not be represented properly . Incorrect placement of the electrodes can lead to serious errors of interpretation .  The re are six chest leads: V1, V2,V3,V4, V5 and V6. V1 At the fourth intercostal space , at the right margin of the sternum V2 At the fourth intercostal space , at the left margin of the sternum V3 Midway between the position of leads V2 and V4 (in a straight line) V4 At the fifth intercostals space at the junction of the left midclavicular line V5 Midway between the position of leads V4 and V6 (straight down from the axillary Line on the same horizontal position as V4 and V6) V6 At the horizontal position of V4, at the left of the midaxillary line.

42. The standard ECG has 12 leads With 12 leads, we need to know which regions of the heart each lead is looking at and what groups they make up. - AVL is on the left wrist or shoulder and looks at the upper left side of the heart. - Lead l travels towards AVL creating a second high lateral lead . - AVf is on the left ankle or left lower abdomen and looks at the bottom, or inferior wall, of the heart. - Lead ll travels from AVr towards AVf to become a 2nd inferior lead - Lead lll travels from AVL towards AVf to become a 3rd inferior lead. - V2 V3 and V4 look at the front of the heart and are the anterior leads. - V1 is often ignored but if changes occur in V1 and V2 only , these leads are referred to as Septal leads. - V5 and V6 look at the left side of the heart and are the lateral leads. - Next slide shows the ECG where these leads are when printed. 3 Standard Limb Leads 3 Augmented Limb Leads 6 Precordial Leads

43. ECG with regions of the heart highlighted

44. BASIC INTERPRETATION OF THE ECG (EKG) Sit back and look - identify the patterns, and write down what you see ! Go through the ECG systematically; Correlate ECG and clinical findings, and if necessary, go back and do a complete rethink; Try and invalidate your assessment --- look for holes !

45. A SYSTEMATIC APPROACH Check the patient details - is the ECG correctly labelled ? What is the rate ? Is this sinus rhythm ? If not, what is going on? What is the mean frontal plane QRS axis (You may wish at this stage to glance at the P and T wave axes too) Are the P waves normal (Good places to look are II and V1) What is the PR interval ? Are the QRS complexes normal? Specifically, are there: significant Q waves ? voltage criteria for LV hypertrophy ? predominant R waves in V1 ? widened QRS complexes ? Are the ST segments normal, depressed or elevated? Quantify abnormalities. Are the T waves normal? What is the QT interval? Are there abnormal U waves ?

46. THANKYOU WISHING YOU THE BEST IN INTERPRETING YOUR ECG SCRIBLES ADIOS!!!!!