EKG Extravaganza!

1. EKG Extravaganza! Michele Ritter, M.D. Argy Resident – Feb. 2007

2. Normal Conduction of the Heart • SA node • Left/Right atrium • Atrial Contraction • AV node • Bundle of His • Purkinjie fibers • Endocardium • Epicardium • Ventricular contraction

3. Generation of EKG

4. Generation of EKG • P wave: • = depolarization/contraction of both atria • QRS complex: • = depolarization/contraction of ventricles • T wave • = rapid phase of ventricular repolarization • ST segment • = plateau phase of ventricular repolarization • QT interval • = ventricular systole

5. Limb Leads Bipolar Lead I – left arm (+) and right arm (-) Lead II – left leg (+) and right arm (-) Lead III – left leg (+) and right leg (-) Unipolar aVR - right arm potentials aVL – left arm potentials aVF – left leg potentials Precordial Leads V1 V2 V3 V4 V5 V6 ECG Leads

6. Precordial Leads

7. Reading EKGs • Rate • Rhythm • Axis • Hypertrophy • Infarction

8. Rate • Large Box = 0.2 seconds • Small Box = 0.04 seconds

9. Rate • 300-150-100-75-60-50 Rule • If one box between R-waves, then rate is 300; If two boxes between, then rate 150, etc. • Rate = 1500/(mm between R waves)

10. What is the rate?

11. Rhythm • Is the rhythm regular (distance between QRS complexes equal)? • Is there a P-wave before every QRS complex? • Is the PR interval normal? • 0.12 sec - 0.20 sec • Is the QRS duration normal? • 0.04 sec to 0.12 sec

12. Irregular Rhythms • Usually caused by multiple, active automaticity sites that causes irregular atrial and ventricular activity • Include: • Wandering Pacemaker • Multifocal Atrial Tachycardia • Atrial Fibrillation

13. Irregular Rhythms • Wandering Pacemaker • Have P’ waves (not true P waves because pacemaker activity is wandering from SA node to a nearby atrial automaticity foci) • Atrial Rate less than 100 • Irregular shape to P waves and irregular ventricular rhythm.

14. Irregular Rhythms (cont.) • Multifocal Atrial Tachycardia • Think of it as tachycardic wandering pacemaker • P’ waves again • Atrial rate excees 100 • Irregular ventricular rhythm • Irregular morphology of P’ waves • Occurs in: • COPD • Heart Disease

15. Irregular Rhythm (cont.) • Atrial Fibrillation • No P waves (because there are multiple atrial automaticity foci sending impulses – no single impulse depolarizes atria completely) • Irregular ventricular rhythm • Caused by: • Heart disease (CAD, CHF) • Thyroid disease • Pericardial effusion • Alcohol

16. Tachy-arrhythmias • Rapid rhythms originating in a very irritable foci that paces rapidly. • Includes:

17. Atrial Tachyarhythmias • Supraventricular tachycardia • Includes paroxysmal junctional tachycardias Paroxysmal Atrial Tachycardia and Paroxysmal Junctional Tachycardia • Caused by very irritable automaticity foci that originate above the ventricles. • Narrow QRS complex tachycardia • Have P’ waves – often get lost in QRS.

18. Supraventricular arrhythmias

19. Atrial Tachyarrhythmias (cont.) • Torsades de Pointes • Rate is usually 250 to 350 beats/min. • The amplitude of each successive complex gradually increases and then gradually decreases – “party streamer” • Caused by: • Severe hypokalemia • Medications that block potassium channels • Congenital abnormality (Long QT syndrome)

20. Atrial Tacchyarrhythmia • Atrial Fibrillation • Rapid Ventricular Response = increased heart rate, putting patient at risk for hypotension.

21. Atrial Tachyarrhythmias (cont.) • Atrial Flutter • Extremely irritable atrial focus produces a rapid series of atrial depolarizations (250-350 beats/min.)

22. Ventricular tacchyarrythmias (cont.) • Paroxysmal Ventricular Tachycardia • Is like a run of PVC’s • Irritable (hypoxic) ventricular focus results in rapid rate that is too fast for heart to function effectively. • WIDE QRS COMPLEX tachycardia

23. Ventricular Tacchyarhythmia (cont.) • Ventricular Fibrillation • Caused by rapid-rate discharges from many irritable, parasystolic entricular automaticity foci. • An erratic, rapid twitching of the ventricles, with ventricular rate reaching 350 to 450 beats/min. • Tracing is totally erratic, without identifiable waves.

24. Tacchyarrhythmia • Wolff-Parkinson-White syndrome • A ventricular “pre-excitation” arrhythmia • An abnormal, accessory AV conduction pathway, the bundle of Kent, can “short circuit” the usual delay of ventricular conduction in the AV node. • Results in • Shortened PR interval (< 0.12 sec) • Widened QRS (> 0.12 sec) • Delta waves • Can result in several tachyarrhythmias including supraventricular tachycardia, atrial flutter, atrial fibrillation

25. Blocks • Sinus Block • AV Block • Bundle Branch Block

26. Sinus Block • SA node fails to pace for at least complete cycle. • Occurs in: • Sick Sinus Syndrome (SSS) • SA node dysfunction resulting recurrent episodes of sinus block or sinus arrest • Frequently occurs in elderly patients with heart disease. • Bradycardia-Tachycardia Syndrome • Patients with SSS who develop episodes of supraventricular tachycardia mingled with sinus bradycradia.

27. AV Block • 1° (first degree) AV Block • Prolongs AV node conduction • Prolonged PR interval (>0.2 sec – one big box) • The PR interval is consistently prolonged the same amount in every cycle • P-QRS-T sequence is normal in every cycle.

28. AV Block (cont.) • 2° (second degree) AV Block • Wenckebach (Mobitz Type I) • Gradually prolongs the PR interval , until the final P wave fails to produce a QRS response. • This cycle then repeats itself. • Usually non-pathologic • Mobitz (Mobitz Type II) • Totally blocks a number of paced atrial depolarizations (P waves) before conduction to the ventricles is successful. • Can be: • 2:1 – two P waves to every QRS • 3:1 – three P waves to every QRS • Usually permanent, and can progress to complete heart block

29. 2° AV Block – “Wenckebach”

30. 2° AV Block - Mobitz 2:1 3:1

31. AV Block - 2° AV block (cont.) • If see 2:1 AV block and uncertain if Wenckebach or Mobitz… • Do vagal maneuver • If Wenckebach, there is an increase the number of cycles/series (increasing to 2:3 or 4:3) • If Mobitz (Type II), it becomes a 1:1 AV conduction.

32. AV Block (cont.) • 3° (third degree) AV block: • “Complete Heart Block” • Complete block of the conduction to the ventricles, so atrial depolarizations are not conducted to the ventricles. • See a sinus-paced atrial (P wave) rate and a totally independent, focus-pased, slow ventricular (QRS rate) – AV dissociation. • Can have: • Junctional Focus • Normal (narrow) QRS • Ventricular rate: 40-60/min. • Ventricular Focus • PVC-like QRS’s • Ventricular rate: 20-40/min.

33. AV Block (cont.) • 3° (third degree) AV Block

34. Bundle Branch Block

35. Bundle Branch Blocks • Caused by block of conduction in the right or left bundle branch. • The bundle branch delays depolarization to the ventricles that it supplies. • Left Bundle Branch Block (LBBB) • Associated with cardiovascular disease! • Incidence increases greatly with age. • Think – V5, V6!! • Right Bundle Branch Block (RBBB) • Associated with structural heart disease, increased age, sometimes iatrogenic (cardiac cath.) • Think – V1, V2!!

36. Bundle Branch Block

37. Left Bundle Branch Block • Widened QRS (> 0.12 sec, or 3 small squares) • Two R waves appear – R and R’ in V5 and V6, and sometimes Lead I, AVL. • Have predominately negative QRS in V1, V2, V3 (reciprocal changes).

38. Right Bundle Branch Block • Widened QRS (> 0.12 sec or 3 small squares) • R and R’ in V1 and V2, often with ST depression and T wave inversion. • Reciprocal changes (big negative S) in V5,V6, I and AVL.

39. Right Bundle Branch Block

40. Bundle Branch Block • Final Note: • If you have the above changes with R and R’, but a normal (not widened) QRS, it is referred to as an incomplete bundle branch block.

41. Axis • The direction of depolarization as it passes through the heart. • A vector towards a lead results in a positive deflection on the ECG, while a deflection away from a lead results in a negative deflection. • If hypertrophy is present, the overall vector (axis) points towards the hypertrophied part.

42. Axis Horizontal Plane Frontal Plane

43. Axis • Normal Axis: QRS vector pointed downard and to the patient’s left, in the 0 to 90° Range. • Right axis Deviation: > 100° • Left axis Deviation: < 0°

44. Axis – the nitty gritty • QRS net positive in Lead I and AVF: normal axis • QRS net positive in Lead I and net negative in AVF: Left axis Deviation • QRS net negative in Lead I and net positive in AVF: Right axis Deviation AVF

45. Axis • Left Axis Deviation: • Can occur in: • Left Ventricular Hypertrophy (hypertension!) • Inferior myocardial infarction • Right Axis Deviation: • Can occur in: • Right ventricular overload (cor pulmonale) • Left pneumothorax • Lateral myocardial infarction.

46. Hypertrophy – we’re going to essentials only. • Left Ventricular Hypertrophy • Important because it is often a sign of long- standing hypertension! • Calculation: • mm of S in V1 + • mm of R in V5 • If sum is more than 35 mm, you have LVH!!! • Remember, you usually see Left axis deviation with LVH.

47. Now the most important…. MYOCARDIAL INFARCTION !!!!

48. EKG in Myocardial Infarction • Gives information about: • Duration — hyperacute/acute versus evolving/chronic • Extent — transmural versus subendocardial • Size — amount of myocardium affected • Localization (which area of heart affected) • Difficult to use EKG in certain situations: • Left bundle branch block • Paced rhythm

49. EKG in myocardial infarction • Ischemia: T waves • Injury: ST changes • Necrosis: Q waves

50. Myocardial Ischemia • Represented by inverted T waves. • Should be symmetrically inverted. • Can be marker of OLD infarction • Wellens syndrome: Marked T wave inversion in V2 and V3, which alerts to stenosis of the left anterior descending coronary artery (LAD)