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 complexesthen 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. 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 LVH

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. 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 Second Degree AV Block

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