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Claude Monet: French Impressionist “Japanese Bridge”

Claude Monet: French Impressionist “Japanese Bridge”. Cardiac Electrophysiology. ECG in Diagnosis Wagner: Chapter 1:3-23. What is an ECG?. Recording : (“gram”) Electrical Activity : (“electro”) Generated by heart cells : (“cardio”) That reach the body surface. E lectro C ardio G ram.

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Claude Monet: French Impressionist “Japanese Bridge”

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  1. Claude Monet: French Impressionist “Japanese Bridge”

  2. Cardiac Electrophysiology ECG in Diagnosis Wagner: Chapter 1:3-23

  3. What is an ECG? • Recording: (“gram”) • Electrical Activity: (“electro”) • Generated by heart cells: (“cardio”) • That reach the body surface ElectroCardioGram

  4. What Does an ECG Measure? • Voltage: Vertical axis • Summation of electrical activity of the total number of cardiac cells • Higher voltage ~ more mass • 12-Leads give 3-D “image” • Time: Horizontal axis • Heart Rate and Rhythm • Lead II or V5-V6 usually

  5. I aVF V1 V4 II aVL V2 V5 V3 III aVR V6 II *Limb Leads: I, II, III, aVF, aVL, aVR *Chest Leads: V1 – V6

  6. What Can ECG Diagnose? • Electrical impulse formation and conduction problems • Cardiac Hypertrophy • Myocardial Ischemia/Infarct • Metabolic Problems: Potassium, calcium and drug toxicity

  7. ECG and CAD • Ischemic Cascade: • Hypoxia = Anaerobic ATP and lactic acidosis • Ventricles “stiffen” diastolic fill • Reduced SV and EF ( CO) • ECG Waveform Changes • Potentially Lethal Arrhythmias

  8. Electrophysiology Review

  9. Myocardial Action Potential 2 +40 1 AP 0 3 0 mV 4 4 -100 ECG

  10. Measured in the Cardiac Cell Resting Potential = -90mV Depolarization = Phase 0 Repolarization = Phase 3 Measured at the Skin Surface Resting Potential = Isoelectric Line Depolarization = +/- deflection Repolarization = “T-Wave” AP ECG

  11. Myocardial Action Potential 2 +40 1 AP 0 3 0 mV 4 4 -100 ECG

  12. ECG Basics • ECG graphs: • 1 mm squares • 5 mm squares • Paper Speed: • 25 mm/sec standard • Voltage Calibration: • 10 mm/mV standard

  13. ECG Paper: Dimensions 5 mm 1 mm Voltage ~Mass 0.1 mV 0.04 sec 0.2 sec Speed = rate

  14. Cardiac Cycle: ECG WAVES • Normal ECG formation / conduction: • P Wave: Atrial depolarization/contraction • QRS Waves: Ventricular depolarization/contraction • T Wave: Ventricular Repolarization

  15. ECG: Cardiac Cycle

  16. Cardiac Cycle Basics: • Begins with SA Node depolarization • P – P = 1 Cycle • Heart rate (pulse) is determined by ventricle depolarization/contraction • R – R = 1 heart beat

  17. Calculating Heart Rates from ECG’s: Step One • Sinus Rhythm: Each QRS complex is preceded by P wave • NSR: Within the intrinsic rate of the SA Node: 60-100 bpm • Tachycardia: >100 bpm • Bradycardia: < 60 bpm

  18. Step Two: • Count the number of small squares between R – R waves (X): • Divide 1500 by X: • Rate = 1500 / X Example: X = 20 1500 / 20 =75 Rate = 75 bpm

  19. Why “1500 / X”? • Paper Speed: 25 mm/ sec • 60 seconds / minute • 60 X 25 = 1500 mm / minute

  20. Activity 1: Cardiac Cycle Identification and Rates • Draw and Label ECG representing one cardiac cycle (see page 18) • Identify the Mechanical Events coinciding with the ECG Wave forms and intervals • Calculate the heart rates for the sample rhythm strips

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