1. ECGs AFMAMS Resident Orientation March 26 2012

2. Lecture Outline ECG Basics Importance of systematically reading ECGs Rate Rhythm Axis Hypertrophy Intervals and Segments Ischemia / Infarction

3. ECG Basics Measurements on ECG paper

4. Identify ECG Landmarks

5. Introduction Be systematic – Rate – Rhythm – Axis – Chamber Hypertrophy Atrial Ventricular – Intervals – Ischemia / Infarction Read Every ECG the same way!

6. How to Determine Rate Rhythm Strip – 10 seconds – Count QRS complexes then multiply by 6 Count Big Blocks between QRS complexes 300-150-100-75-60- 50-43-37

7. Determining Rhythm Look for the P wave – Leads II and V1 Present vs. Absent Regular vs. Irregular Symmetric vs. Asymmetric Normal Sinus Rhythm is most common

8. Normal P wave morphology P wave represents atrial activation The atria activate from right to left, so the first half of the P wave usually represents right atrial activation and the second half represents the left atrium. The sinus node is the usual sight of atrial activation.

10. Definition of Sinus Rhythm NOT “A P wave before every QRS” ACTUAL DEFINITION OF SINUS RHYTHM Normal P wave axis Uniform P wave morphology Regular P-P interval

13. Rhythm P waves: normal sinus (NSR), sinus bradycardia, sinus tachycardia, multifocal atrial tachycardia (MAT), atrial flutter No P waves: atrial fibrillation, junctional rhythm, ventricular fibrillation, ventricular tachycardia Regular: normal sinus, sinus bradycardia, sinus tachycardia, atrial flutter, junctional rhythm, ventricular tachycardia Irregular: atrial fibrillation, multifocal atrial tachycardia, ventricular fibrillation

14. Normal P wave morphology Normal P wave duration: 0.08 – 0.11 seconds Normal P wave amplitude: limb leads < 2.5mm; V1 positive deflection < 1.5mm and negative deflection < 1mm Normal P wave axis: 0-75 degrees Normal morphology: upright in I, II, aVF

15. Normal P wave morphology P wave duration (seconds): measured from the beginning of the P wave to the end of the P wave. Amplitude (mm): measured from the baseline to the top (or bottom). Positive and negative deflections are determine separately.

16. Question: Is this patient in normal sinus rhythm?

17. Axis Refers to the direction of the movement of depolarization spreads through the heart Since left ventricle is the largest and thickest chamber of the heart it undergoes most depolarization Therefore, normal direction of depolarization is from middle of the chest towards the left hip

18. Axis Important in determining – Prior myocardial infarction – Ventricular Hypertrophy – Intraventrcicular Conduction Delay Two methods to calculate axis – Isoelectrical – Short-cut

19. Isoelectrical Calculation Find the isoelectrical QRS complex Axis is perpendicular to isoelectrical axis Use other leads to determine if positive or negative

20. Short Cut Method Look at Lead I and II If QRS positive in Leads I and II – Normal axis If QRS negative in I and positive in II – Right Axis Deviation If QRS positive in I and negative in II – Left Axis Deviation If QRS negative in Leads I and II – Far Right Axis Deviation

21. Atrial Abnormalities Left Atrial Enlargement – Terminal negative P wave in lead V1 >1mm deep and 0.04sec in duration – Notched P wave with a duration >0.12sec in limb leads (I, II) – Seen in: MS, MR, LVH Right Atrial Enlargement – Tall P wave in inferior leads - >2.5mm – Can be seen in: COPD, PE, Pulmonary HTN

25. LVH Cornell Criteria – R in AVL + S in V3 > 28mm (>20mm in females) Voltage Criteria – S in V1 + R in V5/V6 > 35mm – R in AVL > 11mm – Largest R in limb leads >20 Supporting Criteria – LAE – LAD – Prolonged QRS – Strain pattern

27. RVH Right axis deviation (>+90) R V1 >7 mm R V1 + S V5 or V6 >10 mm R/S ratio in V1 >1 S/R ratio in V6 >1 Incomplete right bundle branch block ST-T wave abnormalities ("strain") in inferior leads Right atrial hypertrophy (P pulmonale) S1- S2 - S3 pattern (particularly in children

28. Intervals PR interval QRS Complex QT Interval

30. The PR interval Normal interval: 0.12 – 0.20 seconds in length Short PR interval: < or = 0.11 seconds Long PR interval: > 0.20 seconds

32. Pericarditis Diffuse ST segment depressions PR depression Notching of the S wave

34. Wolf Parkinson White Short PR interval Wide QRS complex Presence of a delta wave ST-T wave changes or abnormalities Clinical association with paroxysmal tachycardias

35. QRS Complex Normal QRS duration – 80 – 120 ms Widened QRS – RBBB – LBBB – Electrolyte abnormalities

36. RBBB Asynchronous activation of the two ventricles increases the QRS duration (0.13 sec). Terminal forces are rightward and anterior due the delayed activation of the right ventricle, Results in an rsR' pattern in the anterior- posterior lead V1 and a wide negative S wave in the lead V6 and Lead I No significant association with risk factors for or the presence of ischemic heart disease, myocardial infarction, or cardiovascular deaths

37. RBBB Criteria QRS > 120 ms rSR’ or rsR’ in V1 Wide S in I, V5 or V6

38. RBBB

39. LBBB Criteria QRS duration > 120 ms QS or rS complex in V1 RsR’ in V6 T wave deflection should be opposite QRS complex (Discordance)

40. LBBB

41. QT Interval Normal – Male < 440 ms – Female < 460 ms Calculated – QTc = QT / RR Prolonged – Electrolytes – Inherited Shortened – Hypercalcemia

42. Long QT

43. Conclusions ECGs are a cheap and readily available diagnostic test ECGs provide a tremendous amount of information Properly interpreting ECGs requires a lot of practice

45. Second Degree AV Block Mobitz Type I – Progressive prolongation of the PR interval until a P wave is blocked – RR interval containing the nonconducted P wave is less than two PP intervals – Usually narrow QRS (block at the level of AV node) Mobitz Type II – Intermittent nonconducted P waves – Constant PR interval – RR interval containing the nonconducted P wave is equal to two PP intervals – Often a wide QRS complex

47. Third Degree AV Block Atrial and ventricular rhythms are independent of one another PP and RR intervals are constant Atrial rate > ventricular rate