Basics of EKG

Importance

• EKG (Electrocardiogram) is a crucial diagnostic tool for clinicians.
• Used to detect:
  • Arrhythmias
  • Myocardial infarctions

Understanding EKG

• EKG represents the electrical activity of the heart through graphical representation.
• Involves understanding cardiac conduction and action potentials.

Cardiac Conduction System

Electrical Activity & Electrodes

• Electrical activity is detected via electrodes:
  • Positive deflection: Activity moves toward the positive electrode.
  • Negative deflection: Activity moves away from the positive electrode.
  • Flat line: Electrical activity is slow or moving perpendicular to the lead axis.

Cardiac Action Potentials

• Understanding movements of electrical activity across heart tissues.
• Lead II used as a reference throughout.

EKG Wave Components

P Wave

• Atrial depolarization, moving from SA node to AV node.

PR Interval

• Delay at AV node (0.1 sec), no net vector direction.
• Important in diagnosing heart blocks (1st, 2nd, 3rd degree).

QRS Complex

• Q Wave: Represents septal depolarization.
• R Wave: Ventricular depolarization, mean QRS vector points towards left due to thicker left ventricle.
• S Wave: Depolarization of ventricular bases.

ST Segment

• Period when ventricles are depolarized but not yet repolarized.

T Wave

• Ventricular repolarization.
• Charge flips from positive to negative.

EKG Leads

Types of Leads

• 12 Lead EKG involves:
  • 3 Bipolar limb leads: Lead I, II, III
  • 3 Augmented unipolar limb leads: aVF, aVL, aVR
  • 6 Precordial (chest) leads: V1 to V6

Bipolar Limb Leads

• Lead I: Right arm to left arm (views from left side)
• Lead II: Right arm to left leg (views from below)
• Lead III: Left arm to left leg (views from below)

Augmented Unipolar Limb Leads

• aVR: Views heart from right side and above.
• aVL: Views heart from left and lateral side.
• aVF: Views heart from inferior aspect.

Precordial (Chest) Leads

• V1, V2: Septum
• V3, V4: Anterior wall
• V5, V6: Left/lateral wall

Clinical Significance

• Diagnosis of MI: Different leads provide insights into specific heart regions.
• Horizontal and Frontal Planes: Provide a comprehensive view of heart activity.

Conclusion

• Understanding EKG involves comprehension of electrical vectors and corresponding deflections.
• Lead II often used for simplicity in demonstration.
• 12-lead EKG provides a detailed 3D view of heart's electrical activity.