ECG and Bioelectric Potentials Quiz

Learning Objectives

• ECG
• EMG
• EEG
• Sleep Study

Bioelectric Potentials

• Purpose of 3, 5, and 12 lead ECGs
• Number of electrodes needed for a 12 lead ECG
• Groups of leads in a 12 lead ECG
• Einthoven Triangle
• Equations for each lead
• Establishing common points in augmented limb leads
• Effect of the right leg in all leads

Electro-Conduction System of the Heart

• Cardiac Axis and 12 Leads ECG
  • 6 unipolar chest leads
  • Location of leads: V1-V6
  • Description of the location of V1-V6 (intercostal space, sternal border, mid-way between V2 and V4, etc.)
  • Wilson terminal equation: VW = (VLA + VRA + VLL)/3
  • Leads V1 to V6 calculations using Wilson terminal (VCn – VW)
  • Diagram of Electro-Conduction System of the Heart, showing the placement of the leads

Rhythm Strip

• ECG is printed on standard thermal strips
• Small square = 1 mm x 1 mm, big square = 5 mm x 5 mm
• Horizontal axis = time, vertical axis = voltage
• Standard setting = 25 mm/s recording speed and x1 sensitivity
• Equals 0.04s/small square and 0.1mV/small square
• Calculating heart rate (HR) from rhythm strip (regular rhythm method)
  • Number of squares per minute = 1500 (or 25mm/s X 60s)
  • Number of squares per R-R interval
  • HR = 1500/x = (where x is the number of squares per R-R interval)
• Calculating HR from rhythm strip (irregular rhythm method)
  • Number of R-R intervals in a 6-second period (y)
  • HR = y * 10

Cardiac Arrhythmias

• Slow or fast rhythm (Bradycardia & Tachycardia)
• Propagation delays (e.g., PR timing)
• Conduction blockage (e.g., AV block)
• Cardiac arrest
• Fibrillation (atrial or ventricular)
• Asystole

Electrocardiograph (ECG Machine)

• Components
  • Sensing electrodes
  • Protection circuit
  • Lead selector
  • Lead-fail detector
  • Auto calibration
  • Bio-amplifier
  • Driver, right-leg circuit
  • Isolation circuit
  • Preamplifier
  • Baseline restoration
  • Memory
  • ADC
  • Recorder Printer
  • Micro-controller
  • Control program
  • Operator display
  • Keyboard
  • Power Supply
• Functions –detailed explanation to each component
  • Pick up ECG signals from the body
  • Prevent high voltage damage
  • Select appropriate leads (auto/manual)
  • Detect unconnected/ dry electrodes
  • Calibrate preamplifier and recorder
  • Digitize analogue signals (ECG signal)
  • Amplify ECG signals
  • Restore baseline stability in recordings
  • Ensure isolation between patient and equipment

Summary

• Cardiac Axis and 12 Leads ECG : Wilson terminal equation, Lead calculations
• Rhythm Strip –HR calculation : Regular rhythm, Irregular Rhythm Method
• Electrocardiograph (ECG Machine): Block Diagram

Test your knowledge on ECG, EMG, EEG, and sleep study techniques. This quiz covers various aspects of heart electro-conduction and the setup of 12 lead ECGs, including lead placement and calculations. Dive into the details of cardiac axis and rhythm strips as you enhance your understanding of bioelectric potentials.