ECG Basics Module 2( Arrhythmias level 1)

1. ECG Basics Module 2( Arrhythmias level 1) Dr. Jeffrey Elliot Field, HBSc. DDS, Fellow, American Dental Society of Anesthesia Diploma, the National Dental Board of Anesthesia. • 1 8/24/2014

2. OBJECTIVES • TO LEARN TO INTERPRET BASIC ARRYTHMIAS

4. Lets Review What an ECG Is. • An ECG is a recording of the electrical activity within heart muscle. • Heart muscle unlike other muscle can contract without a an external nerve input or action potential. • The interesting thing about cardiac muscle is: • it can depolarize as the result of adjacent cells depolarizing. Like a wave in the crowd at a football game. • Pacemaker cells can spontaneously depolarize as a result of spontaneous intracellular mechanisms. • All other muscle cells only depolarize as the result an external mechanism ( motor neuron stimulation) • This depolarization and repolarization cycle is what we see on an ECG

5. Basic Cardiac Physiology • The pacemaker sites within the heart are the SA node, AV node and Purkinge fibers in the heart. • As discussed earlier each pacemaker site within the heart has its own unique firing rate. • As a result the heart rate can often be a clue as to which pacemaker is in charge at that point in time. ( see diagram on next slide)

7. HOW TO READ A THREE LEAD RYTHYM STRIP

8. The 3 Steps In ECG Determination Are: • 1) Establish whether are not there is there electrical activity. • 2)Rate determination. • 3) Rhythm identification.

9. STEP 1 • IS THERE ANY ELECTRICAL ACTIVITY? • IF NO ACTIVITY IS SEEN YOU MUST FIRST CHECK THE LEADS ARE ADHERING TO THE SKIN AND ALL CONNECTIONS ARE INTACT. • IF THE CONNECTIONS ARE ALL OK, THEN CHECK THE PULSE. IF NO PULSE EXISTS AND IF EVERYTHING IS HOOKED UP PROPERLY AND THERE IS NO ELECTRICAL ACTIVITY ,THEN A DIAGNOSIS OF ASYSTOLE IS MADE.

10. Note: In asystolethe straight baseline wanders. If a true straight line exists this usually indicates that a lead has come loose. • 10 8/24/2014

11. P wave Asystole • 11 In this case asystole exists even though there is P wave electrical activity . Please note that there is NO ventricular activity and therefore NO blood Flow. 8/24/2014

12. AGONAL RYTHYM • This is another example of asystole in which the heart displays the last moments of it’s electrical activity. This rhythm is also called dying heart.

13. To REVIEW , THESE ARE THE THREE FORMS OF ASYSTOLE

14. Step 2 Basic Rhythm Determination Next if there is electrical activity is there a rhythm ? • If there is no rhythm then think about ventricular fibrillation ( V-fib). • V-fib can be categorized as follows: • Fine V-fib • Coarse V-ifib • Torsades De Pointes ( twisting pointes)

15. Fine V-Fib

16. Coarse V-fib

17. Torsades de pointes ( twisting points) This is often a sign of hypomagnesemia ( low magnesium)

18. What,s really happening in V-Fib ?

19. Immediate action is required!!!

20. STEP 2 RATE DETERMINATION

21. HOW TO EVALUATE TIME/RATE ON STANDARD ECG PAPER There are 15 large boxes in every 3 seconds

22. Since the ECG paper moves at 25 mm/second and therefore 25 of the 1.0 mm ( small)boxes or 5 of the big boxes pass in one second. • Therefore 1 small box = 0.04 seconds and 5 small boxes or 1 big box =0.20 seconds( as discussed in module1). • Now you have all the information you need to calculate rates

23. There Are 3 Methods To Determine Rate • 1) Counting the R-waves per minute with respect to the large boxes on the ECG paper. • 2)Quick rate determination • ) Counting R-waves per minute with respect to small boxes on the ECG paper.

24. QUICK METHOD FOR RATE DETERMINATION. • It is possible to now calculate rate by counting the number of R waves in one minute. However this is very tedious and time consuming. • The quick method involves memorizing the following chart which entails counting the number of large boxes ( i.e. 5 small boxes) between R waves.

25. Quick Method of Rate Determination Number of large boxes between R-waves 1 2 3 4 5 6 7 8 9 10

26. A final method is to count the number of small ( 1.0mm) boxes between 2 consecutive R waves and divide this into 1500.

27. CAN YOU DETERMINE THIS RATE? 75 bpm

28. RATE NOMENCLATURE • Normal heart rates are from 60-100 beats per minute. • Rates above 100 are termed tachycardia. • Rates below 60 are termed bradycardia.

29. Tachycardias • Tachycardia's can be divided into two groups. • -Supraventricular are tachycardia's in which the pacemaker site is above the AV node. In this case the QRS width is normal (under 0.12 seconds or 3 small boxes) • Supraventricular tachycardia's are: • Paroxysmal super ventricular tachycardia( an SVT that comes and goes) • Supraventricular tachycardia( a sustained SVT) • Atrial flutter( a characteristic type of sustained SVT) • Ventricular Tachycardia's ( also called wide complex tachycardia's) are tachycardia’s in which the pacemaker lies below the AV node. In this case the QRS width is prolonged. (over 0.12 seconds or 3 small boxes)

30. Superventricular Tachycardia Atrial Flutter ( Note the characteristic sawtooth pattern)

31. Classic Ventricular Tachycardia ( VTACH) Ventricular Tachycardia with Capture Beats( see ). That is there are quasi normal beats interspersed between the wide complex beats.  

32. Clinical Relevance of Tachycardias • With each heart beat blood is ejected from the ventricles . • 70% of the refill of the ventricles is passive. That is after the ventricle squeezes the blood out it relaxes and blood is passively drawn in. • The final 30% of ventricular filling is the result of active pushing of blood from the atria ( also called the atrial kick) . With atrial flutter and atrial fibrillation you loose the atrial kick.

33. 33 also as the rate increases the time available for passive ventricular filling is decreased. therefore less and less blood is moved which leads to a decrease in the pulse or even loss of the pulse. In this case the organs and tissue receive little or no blood and in turn little or no oxygen. With atrial flutter and atrial fibrillation the loss of the atrial kick ends in poor tissue perfusion. This is also called a loss of perfusion pressure. 8/24/2014

34. Rhythm Determination

35. STEP 3 IS TO DETERMINE THE RYTHYM • This is done by looking at the following factors. • -Is the rhythm regular or irregular • -Is the QRS complex width normal or prolonged • -Is atrial activity present and if present how does the atrial activity relate to the ventricular activity

36. IS THE RYTHYM REGULAR OR IRREGULAR • Look at the R-R intervals and see if they all are the same. • If so the rhythm is regular. • If not, is the rhythm totally irregular ? {“ irregularly irregular”} • or is there cyclical variation (i.e. the pattern is irregular but repeats)

37. Use calipers to mark out the R-R interval and see if it repeats. If it does, it’s a regular rhythm and if it doesn’t, it is irregular.

38. Regular Rhythms

39. Sinus Rhythm • Diagnosis of Sinus Rhythm • P-waves are present, upright and precede each QRS complex • The P-R interval is normal (0.12-2.0 seconds) • QRS complexes are of normal (less than o.12 seconds) size and morphology( no pathologic Q waves-see later module) • The Q-T interval is normal in duration ( around 10 small boxes based on rate-see later discusson on the QT interval) • The T-wave is upright

40. Paced Rhythm       Note the pacer spikes which generate a QRS complex

41. Irregular Rhythms

42. IRREGULARLY IRREGULAR Rhythm • This is always atrial fibrillation. • In this case the atrial cells are firing off in a non coordinated pattern which causes the atria to quiver rather than contract. This of course moves NO BLOOD. • Blood still however moves between the atria and ventricles but only via passive filling such that you loose the 30% of ventricular filling given by the atrial kick. • Different pacemaker sites within the atria in random order cause ventricular depolarization, which leads to the irregularly irregular rhythm.

43. Atrial fibrillation Note there are no P-waves. You can see QRS complexes but there is NO PATTERN to the R-R interval. That is each R-R interval is different. Hence the rhythm is irregularly irregular.

44. OTHER CAUSES OF IRREGULAR, BUT CYCLICALLY REPEATING RYTHYMS • Ectopic beats such as: • -PVC’s ( Premature ventricular contractions). • -Junctional Escape rhythms • PAC’s ( Premature atrial contactions) -Escape beats where a pacemaker in the atria other than the SA node generates the beat. • Heart Blocks or AV nodal blocks

45. PVC’s Classification • PVC’s are a premature ventricular contraction. That is the ventricle contracts on its own, without receiving a signal from the SA node.These are classified as follows: • 1)UNIFOCAL( originating from the same site in the ventricle). Therefore all PVC’s look exactly alike. • 2) MULTIFOCAL( originating from different sites in the ventricle). Such that the PVC’s have different morphologies. • 3) PVC Nomenclature: BIGEMINY ( one normal beat alternating with a PVC) , TRIGEMINY two normal beats followed by a PVC) etc .

46. Examples of Unifocal and Mutifocal PVC’s

47. Unifocal PVC ( both PVC’s look alike) ↑ ↑

48. Multifocal PVC’s ↑ ( with run of unifocal PVC’s) (↑ run of unifocal PVC’s) ↑ ↑↑↑ ↑

49. Why are PVC’S Important?

50. The Answer is the R on T Phenomenon • In these cases if a PVC’s R-wave falls on the previous QRS’s T-wave, this can generate a run of ventricular fibrillation. • This usually is not an issue with single unifocal PVC’s but becomes a worry in cases with multifocal PVC’s or runs of unifocal PVC’s. In these cases you should treat the PVC’s with either lidocaine or amiodarone.