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EKG 101

EKG 101. Deborah Goldstein Georgetown University Department of Internal Medicine. Steps to Interpreting an EKG. Rate Rhythm Axis Intervals (PR, QRS, QTc) Hypertrophy ST segments T waves Q waves. Rate. Naming stuff. Normal Sinus Rhythm. P before every QRS

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EKG 101

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  1. EKG 101 Deborah Goldstein Georgetown University Department of Internal Medicine

  2. Steps to Interpreting an EKG • Rate • Rhythm • Axis • Intervals (PR, QRS, QTc) • Hypertrophy • ST segments • T waves • Q waves

  3. Rate

  4. Naming stuff

  5. Normal Sinus Rhythm • P before every QRS • Best places to look: II, V1 • QRS after each P

  6. Axis 1. The direction of the mean electrical vector, representing the average of current flow in the frontal plane. 2. Normal axis: –30 to +90 degrees.

  7. Axis

  8. Axis • Look at lead I and aVF. • Then find the isoelectric lead (where the QRS complex is most nearly biphasic). • Then go 90 degrees perpendicular to the isoelectric lead.

  9. Axis

  10. Axis

  11. Rate, Rhythm, Axis

  12. Rate, Rhythm, Axis

  13. Rate, Rhythm, Axis

  14. Ddx of Axis Deviation LAD • Left ventricular hypertrophy, Left anterior fascicular block, LBBB, Inferior wall MI • Pregnant, ascites, short/fat RAD • Right ventricular hypertrophy, Left posterior fascicular block, RBBB, lateral wall MI • PE

  15. PR Interval • Normal PR = 0.12 – 0.20 seconds (3-5 little boxes) • Long PR >0.20 seconds (>5 little boxes) =Delayed conduction from atria to ventricles • First-degree AV block • PR>0.20 seconds • NO dropped QRS

  16. Second Degree AV Block • Wenckebach (Type 1) =block within AV node • PR interval progressively lengthens...then dropped QRS • Mobitz (Type 2) =block within His-Purkinje system • Fixed PR with dropped QRS • WORSE! • Sarcoid, Lyme.... • Pacemaker!

  17. Third Degree AV Block =Failure of conduction of any atrial impulses to get to the ventricles =Complete AV block Causes of Acute AV Block: • Calcium channel blockers • Acute RCA occlusion • Digoxin toxicity

  18. What kind of AV Block?

  19. What kind of AV Block?

  20. What kind of AV Block?

  21. What kind of AV Block?

  22. QRS Interval Normal = 0.06-0.10 seconds Wide QRS = >0.12 seconds (>3 little boxes) • PVC...if >3 in a row or >6/min=VTach • RBBB, LBBB • Left fascicular hemiblock • Hyperkalemia Narrow QRS= <0.06 sec • SVT (150-250 bpm) • Idiojunctional rhythm (40-60 bpm) • Premature junctional complex

  23. Chest Leads V6 V1

  24. Bundle Branch Block V1-V2 = Right precordial leads V5-V6 = Left precordial leads LBBB • Rabbit ears in V6 represent delay between depolarization from the septum  to the LV RBBB • Rabbit ears in V1 represent delay between depolarization from the septum to the RV

  25. V1 V6 Normal: V1: rS complex V6: qR complex RBBB: V1: Rabbit Ears (rSR) V6: qRS complex LBBB: V1: wide QS complex V6: Rabbit Ears

  26. Wide QRS—Why?

  27. Wide QRS—Why?

  28. QT Interval • Should be < ½ (R-R’ interval) • Measure from the start of the QRS to end of T wave • Varies with heart rate, so correct for RR interval • Normal QTc: women=0.44, men=0.42 • QTc = QT (#of small squares) x 0.04 √RR • Long QT can lead to ‘R on T’Death

  29. Causes of Long QT **Think ‘Lytes and Meds first! • Low K, Low Ca, Low Mg • Macrolides, Quinolones • All Antipsychotics (Haldol worst, Geodon least) • SSRIs • Sotalol, Quinidine, Ondansetron, Amio, TCAs • Pts w/LVH or CHF are predisposed to medication-related lengthening of QT interval! • Avoid Macrolides, Quinolones in them!

  30. Long QT: Less common causes • Hypothyroid • Hypothermia • AV Block • MI • CVA • Head injury • Congenital long QT

  31. Atrial Enlargement RAE • P wave is tall and peaked (>2.5mm high) • OR Biphasic P wave with initial positive inflection • Ddx: Pulmonary HTN, COPD, PE LAE • P wave is wide (>0.12 sec) and notched in the middle “M” • OR Biphasic P wave with terminal negative inflection • Ddx: Systemic HTN, Aortic Insufficiency, Mitral Stenosis

  32. Which Atria is Enlarged?

  33. Which Atria is Enlarged? II V1

  34. LVH Criteria • Sokolow + Lyon • S V1+ R V5 or V6 > 35 mm • Cornell criteria (Circulation, 1987;3: 565-72) • S V3 + R avl > 28 mm in men • S V3 + R avl > 20 mm in women • Framingham criteria (Circulation,1990; 81:815-820) • R avl > 11mm, R V4-6 > 25mm • S V1-3 > 25 mm, S V1 or V2 + • R V5 or V6 > 35 mm, R I + S III > 25 mm • Romhilt + Estes (Am Heart J, 1986:75:752-58) • Point score system (Am Heart J, 1999;37:161)

  35. LVH “S V1+ R V5 or V6 > 35mm”

  36. ST changes: axis + anatomy • Lateral: • I, aVL • LCA, CFX • Anterior: • V1, V2, V3, V4 • LAD Inferior: -II, III and aVF -RCA (or LCA) Memorize this slide

  37. Q waves • Normal Q wave: • Small septal Qs in I, aVL, V5, V6 • Isolated Qs in III, V1 • Pathologic Q wave: • wider than 1 small box (0.04 sec) • OR >25% height of the R wave in that complex

  38. Normal Q waves

  39. Abnormal Q Waves

  40. Non-ST Elevation MI =Severe subendocardial ischemia • Marked, diffuse ST depressions in I, II, III, aVL , aVF , V2-V6

  41. 2 EKGs, several hours apart

  42. Acute ST Elevation MI • Normal • Hyperacute • T wave Elevation • Acute • ST Elevation • Hours Later • ST Elev, Q begins to form, T wave inverts • Days Later • Q wave, T wave inversion • Weeks Later • Q wave

  43. A 55 year old man with 4 hours of "crushing" chest pain.

  44. Acute Inferior Wall MI • ST elev in II, III, AVF • Reciprocal ST depression in anterior leads (V2-V4) =RCA occlusion (some LCx)

  45. A 53 year old man with Ischemic Heart disease

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