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Cardiac Ecg Interpretation
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Cardiac Ecg Interpretation


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  • 1. What you will learn • Understanding preload, afterload, and contractility. • Phases of the cardiac cycle (revision) • Linking the ‘phases’ to the ECG • How electrolyte imbalances affect ECG’s • Acute AF,MI,
  • 2. eartscape_2004.html Testing your cardiac knowledge!
  • 3. Preload, afterload & contractility. • If you think of the heart as a balloon, it will help you understand stroke volume!
  • 4. Phases of the Cardiac Cycle. • What can you remember? • Do not worry how many phases there are, as long as you remember the ‘process’
  • 5. Phase 1 • Are the A-V Valves open or closed? • Are the Semilunar Valves open or closed? • Is this polarization or depolarization of the Atrial? • The pressure within the atrial chambers increase or decrease? (remember balloon) • What part of the ECG does this represent?
  • 6. Where do I start! • P-wave is the depolarization of the Atrium • QRS-wave is the depolarization of the Ventricles • There should be one P-wave to each QRS • Normal P to R interval should be less than 0.2 seconds or five little boxes • Normal QRS interval should be less than 0.12 seconds or three little boxes • Normal heart rate is 60-100 • Bradycardia is heart rate less than 60 • Tachycardia is heart rate greater than 100
  • 7. Simplified! • Step 1. Is the speed of the rhythm between 60-100? Step 2. Is it regular? Step 3. Is the complex narrow? Step 4. Is it preceded by a P-wave? Step 5. Do all the complexes look the same?
  • 8. Let us now look at a normal ECG trace.
  • 9. How does the ECG work?
  • 10. • Vertical and horizontal perspective of the leads. The limb leads “view” the heart in the vertical plane and the chest leads in the horizontal plane
  • 11. Unipolar, Bipolar and Precordial leads. • The word ‘leads’ is misleading. Sometimes it is used to mean the pieces of wire that connect the patient to the ECG recorder. Properly, a lead is an electrical picture of the heart.
  • 12. Sinus Rhythm • Sinus denotes that the rhythm of the heart is still being generated by the sinuatrial node, so the P-wave and QRS complex are generally normal.
  • 13. Sinus Rhythm
  • 14. How electrolyte imbalances affect ECG’s • The electrolytes sodium, potassium, and calcium, with the help of magnesium, shift back and forth across myocardial cell membranes. • This shifting of electrolytes causes alternating periods of activity (depolarization) and rest (repolarisation), which allow for normal myocardial function.
  • 15. Hypokalemia • Serum potassium < 3.5 mEq/L • Ventricular repolarisation is prolonged. • The ECG shows a characteristic U wave • Ectopic impulses develop in the myocardium • A rhythm strip may show ventricular ectopy • Potentially fatal arrhythmias such as ventricular tachycardia.
  • 16. Ventricular ectopics
  • 17. Ventricular Tachycardia
  • 18. Ventricular Tachycardia
  • 19. Anyone want to hazard a guess?
  • 20. Hyperkalemia • Serum potassium > 5.5 mEq/L • A tall tented T wave • AV or ventricular block may develop • Flattened P wave • A prolonged PR interval • A widened QRS complex • Depressed ST segment • Severe Hyperkalemia > 9 mE/L causes the P wave to disappear, the QRS complex to widen, and sine waves to form. Hyperkalemia may end in lethal arrhythmias.
  • 21. Atrial fibrillation
  • 22. Atrial flutter
  • 23. CASE STUDY • A 58-year-old male, presents to ED with C/O chest pain, with radiation to the Left arm and jaw. He reports feeling anxious, diaphoretic, and SOB. His PMH is significant of type II diabetes mellitus and hyperlipidemia. O/E, the patient appears to be in moderate distress and anxious. His ECG shows evidence of Acute MI in the inferior leads. The Dr. suspects that the left anterior descending artery is involved.
  • 24. Case study continued • What would the ST segment of this ECG look like? • On which leads would you see this ST segment change? • What does the T wave represent
  • 25. MI • The normal electrocardiogram (ECG) pattern consists of a P wave, a QRS complex, and a T wave (A). • In patients who have an ST elevation myocardial infarction (MI), the ST segment is elevated above the baseline (B). • In patients who have a non-ST elevation MI, the ST segment is not elevated, and instead other patterns are seen (for example, ST depression) (C).
  • 26. Answers • ST segment appearance: Elevation of the ST segments. • Inferior leads: II, III, and aVf • T wave: Represents ventricular polarizion.
  • 27. ECG recognition quiz • Choose one of the following answers (A – E) • A. – P wave • B. – PR wave • C. – QRS complex • D. – ST segment • E – T wave 1. Period when ventricular action potentials are in their plateau phase. 2. Prolonged during first-degree heart block 3. Produced by depolarization of atrial fibers
  • 28. Any question? • To summarise: • We have reviewed the pathophsyiology of the heart. • Wetted your appetite for ECG recognition.