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- 1. What is an ECG? The electrocardiogram (ECG) is a representation of the electrical events of the cardiac cycle. Each event has a distinctive waveform, the study of which can lead to greater insight into a patient’s cardiac pathophysiology.
- 2. The 12-Leads The 12-leads include: –3 Limb leads (I, II, III) –3 Augmented leads (aVR, aVL, aVF) –6 Precordial leads (V1- V6) For more presentations www.medicalppt.blogspot.com
- 3. The ECG Paper • Horizontally – One small box - 0.04 s – One large box - 0.20 s – 5 Large squares = 1 second • Vertically – One large box - 0.5 mV For more presentations www.medicalppt.blogspot.com
- 4. Anatomy of Heart Conduction and ECG signal
- 5. Pacemakers of the Heart • SA Node - Dominant pacemaker with an intrinsic rate of 60 - 100 beats/minute. • AV Node - Back-up pacemaker with an intrinsic rate of 40 - 60 beats/minute. • Ventricular cells - Back-up pacemaker with an intrinsic rate of 20 - 45 bpm.
- 6. Rhythm Analysis HOW TO ANALYSE THE RHYTHM? • Step 1: Calculate rate. • Step 2: Determine regularity. • Step 3: Assess the P waves. • Step 4: Determine PR interval. • Step 5: Determine QRS duration. For more presentations www.medicalppt.blogspot.com
- 7. Step 1: Calculate Rate 1)Count the number large squares R wave between two consecutive “R” waves then devide the result by 300 → For regular H.R i.E 300/4 = 75bpm 2) Count the number of “R” waves in 6 seconds strip(30 large squares) then multiply the result by 10 → For irregular H.R i.E 10×12=120bpm Option 3 – Find a R wave that lands on a bold line. – Count the # of large boxes to the next R wave. If the second R wave is 1 large box away the rate is 300, 2 boxes - 150, 3 boxes - 100, 4 boxes - 75, etc. – Memorize the sequence: 300 - 150 - 100 - 75 - 60 - 50 • • R-R interval is ventricular rate For more presentations p-p interval is atrial rate. Usually www.medicalppt.blogspot.com the same but not always
- 8. Step 2: Determine regularity R R • Look at the R-R distances (using a caliper or markings on a pen or paper). • Regular (are they equidistant apart)? Occasionally irregular? Regularly irregular? Irregularly irregular? Interpretation? Regular For more presentations www.medicalppt.blogspot.com
- 9. Step 3: Assess the P waves • Are there P waves? • Do the P waves all look alike? • Do the P waves occur at a regular rate? • Is there one P wave before each QRS? Normal P waves with 1 P Interpretation? wave for every QRS For more presentations www.medicalppt.blogspot.com
- 10. Step 4: Determine PR interval • Normal: 0.12 - 0.20 seconds. (3 - 5 boxes) Interpretation? 0.12 seconds For more presentations www.medicalppt.blogspot.com
- 11. Step 5: QRS duration • Normal: 0.04 - 0.12 seconds. (1 - 3 boxes) Interpretation? 0.08 seconds
- 12. Rhythm Summary • Rate • Regularity • P waves • PR interval • QRS duration Interpretation? 90-95 bpm regular normal 0.12 s 0.08 s Normal Sinus Rhythm For more presentations www.medicalppt.blogspot.com
- 13. NSR Parameters • Rate 60 - 100 bpm • Regularity regular • P waves normal • PR interval 0.12 - 0.20 s • QRS duration 0.04 - 0.12 s Any deviation from above is sinus tachycardia, sinus bradycardia or an arrhythmia For more presentations www.medicalppt.blogspot.com
- 14. Arrhythmia Formation Arrhythmias can arise from problems in the: •Sinus node •Atrial cells •AV junction •Ventricular cells – AN ABNORMALITY OF THE RHYTHM OR RATE OF THE HEARTBEAT CALLED ARRHYTHMIA CAUSED BY DISTURBENCE IN THE ELECTRICAL IMPULSES IN THE HEART For more presentations www.medicalppt.blogspot.com
- 15. SA Node Problems The SA Node can: • fire too slow • fire too fast Sinus Bradycardia Sinus Tachycardia Sinus Tachycardia may be an appropriate response to stress. For more presentations www.medicalppt.blogspot.com
- 16. Sinus Bradycardia Rhythm #1 • Rate? • Regularity? • P waves? • PR interval? • QRS duration? Interpretation? 30 bpm regular normal 0.12 s 0.10 s Sinus Bradycardia SA node is depolarizing slower than normal, impulse is conducted normally (i.e. normal PR and QRS interval).
- 17. Sinus Tachycardia Rhythm #2 • Rate? • Regularity? • P waves? • PR interval? • QRS duration? Interpretation? 130 bpm regular normal 0.16 s 0.08 s Sinus Tachycardia Etiology: SA node is depolarizing faster than normal, impulse is conducted normally. Remember: sinus tachycardia is a response to physical or psychological stress, not a primary arrhythmia.
- 18. Atrial Cell Problems Atrial cells can: • fire occasionally from a focus Premature Atrial Contractions (PACs) • fire continuously due to a looping re-entrant circuit Atrial Flutter • Atrial cells can also: • fire continuously from multiple foci or Atrial Fibrillation • fire continuously due to multiple micro reentrant “wavelets” For more presentations www.medicalppt.blogspot.com
- 19. Premature Atrial Contractions Rhythm #3 • Rate? • Regularity? • P waves? • PR interval? • QRS duration? Interpretation? 70 bpm occasionally irreg. 2/7 different contour 0.14 s (except 2/7) 0.08 s NSR with Premature Atrial Contractions
- 20. Premature Atrial Contractions • Deviation from NSR – These ectopic beats originate in the atria (but not in the SA node), therefore the contour of the P wave, the PR interval, and the timing are different than a normally generated pulse from the SA node. For more presentations www.medicalppt.blogspot.com
- 21. Atrial Fibrillation Rhythm #4 • Rate? • Regularity? • P waves? • PR interval? • QRS duration? Interpretation? 100 bpm irregularly irregular none none 0.06 s Atrial Fibrillation Impulses take Multiple, Chaotic, Random pathways through atria
- 22. Atrial Flutter Rhythm #5 • Rate? • Regularity? • P waves? • PR interval? • QRS duration? Interpretation? 70 bpm regular flutter waves none 0.06 s Atrial Flutter Impulses take a circular course around the atria, setting up a flutter waves
- 23. AV Junctional Problems The AV junction can: • fire continuously due to a looping re-entrant circuit Paroxysmal Supraventricular Tachycardia • block impulses coming AV Junctional Blocks from the SA Node For more presentations www.medicalppt.blogspot.com
- 24. Paroxysmal Supraventricular Tachycardia Rhythm #6 • Rate? • Regularity? • P waves? • PR interval? • QRS duration? Interpretation? 74 148 bpm Regular regular Normal none 0.16 s none 0.08 s (PSVT) Impulses recycle repeatedly in the AV node , There are several types of PSVT but all originate above the ventricles (therefore the QRS is narrow).
- 25. 1st Degree AV Block Rhythm #7 • Rate? • Regularity? • P waves? • PR interval? • QRS duration? •Interpretation? 60 bpm regular normal 0.36 s Prolonged 0.08 s 1st Degree AV Block Impulse conduction is slowed at AV node for a fixed interval
- 26. 2nd Degree AV Block, Type I Rhythm #8 • Rate? • Regularity? • P waves? • PR interval? • QRS duration? Interpretation? 50 bpm regularly irregular nl, but 4th no QRS lengthens 0.08 s 2nd Degree AV Block, Type I Impulse conduction is slowed at AV node, until one sinus impulse is completely blocked and QRS complex fail to follow
- 27. 2nd Degree AV Block, Type II Rhythm #9 • Rate? • Regularity? • P waves? • PR interval? • QRS duration? Interpretation? 40 bpm regular nl, 2 of 3 no QRS 0.14 s 0.08 s 2nd Degree AV Block, Type II Site of the block is often below the AV node at bundle of His or bundle branches ( 2 dropped beats)
- 28. 3rd Degree AV Block Rhythm #10 • Rate? • Regularity? • P waves? • PR interval? • QRS duration? Interpretation? 40 bpm regular no relation to QRS none wide (> 0.12 s) 3rd Degree AV Block Injury or damaged to cardiac conduction system
- 29. Ventricular Cell Problems Ventricular cells can: • fire occasionally from 1 Premature Ventricular or more foci Contractions (PVCs) • fire continuously from multiple foci Ventricular Fibrillation • fire continuously due to Ventricular Tachycardia a looping re-entrant circuit For more presentations www.medicalppt.blogspot.com
- 30. Sinus Rhythm with 1 PVC Rhythm #11 • • • • • Rate? Regularity? P waves? PR interval? QRS duration? Interpretation? 60 bpm occasionally irreg. none for 7th QRS 0.14 s 0.08 s (7th wide) Sinus Rhythm with 1 PVC For more presentations www.medicalppt.blogspot.com
- 31. PVCs • Deviation from NSR – Ectopic beats originate in the ventricles resulting in wide and bizarre QRS complexes. – When there are more than 1 premature beats and look alike, they are called “uniform”. When they look different, they are called “multiform”. For more presentations www.medicalppt.blogspot.com
- 32. Ventricular Tachycardia Rhythm #12 • Rate? • Regularity? • P waves? • PR interval? • QRS duration? Interpretation? 160 bpm regular none none wide (> 0.12 sec) Ventricular Tachycardia Impulse conduction slowed around ventricular injury , or ischemia
- 33. Ventricular Tachycardia • Etiology: There is a re-entrant pathway looping in a ventricle (most common cause). • Ventricular tachycardia can sometimes generate enough cardiac output to produce a pulse; at other times no pulse can be felt. For more presentations www.medicalppt.blogspot.com
- 34. Ventricular Fibrillation Rhythm #13 • Rate? • Regularity? • P waves? • PR interval? • QRS duration? Interpretation? none irregularly irreg. none none wide, if recognizable Ventricular Fibrillation Ventricles consist of areas of normal myocardium alternating with areas of ischemic, injured, or infarcted myocardium, leading to chaotic pattern of ventricular depolarization
- 35. Ventricular Fibrillation Coarse VF Fine VF • Etiology: The ventricular cells are excitable and depolarizing randomly. • Rapid drop in cardiac output and death occurs if not quickly reversed For more presentations www.medicalppt.blogspot.com
- 36. Pulseless electrical activity Rhythm #13 • Rate? • Regularity? • P waves? • PR interval? • QRS duration? Interpretation? none Regular present Normal 0.10 PEA Any organized rhythm without detectable pulse is “PEA” Cardiac conduction impulses occur in organized pattern, but this fails to produce myocardial contraction
- 37. Asystole Rhythm # 14 •Rate: no ventricular activity seen or ≤6/min; so-called “Pwave asystole” occurs with only atrial impulses present to form P waves • Rhythm: no ventricular activity seen; or ≤6/min • PR: cannot be determined; occasionally P wave seen, but by definition R wave must be absent • QRS complex: no deflections seen that are consistent with a QRS complex Asystole: agonal complexes too slow to make this rhythm
- 38. Diagnosing a MI To diagnose a myocardial infarction you need to go beyond looking at a rhythm strip and obtain a 12-Lead ECG. 12-Lead ECG Rhythm Strip For more presentations www.medicalppt.blogspot.com
- 39. ST Elevation One way to diagnose an acute MI is to look for elevation of the ST segment. For more presentations www.medicalppt.blogspot.com
- 40. ST Elevation (cont) Elevation of the ST segment (greater than 1 small box) in 2 leads is consistent with a myocardial infarction. For more presentations www.medicalppt.blogspot.com
- 41. ECG Changes : Ischemia • • • • T-wave inversion ( flipped T) ST segment depression T wave flattening Biphasic T-waves Baseline 2004 Anna Story 45
- 42. ECG Changes: Injury • ST segment elevation of greater than 1mm in at least 2 contiguous leads • Heightened or peaked T waves • Directly related to portions of myocardium rendered electrically inactive Baseline 2004 Anna Story 46
- 43. 2004 Anna Story 47

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