5-1. Lesson 5 (cont) Introduction to ECG Rhythm Analysis

Things to Consider When Analyzing Arrhythmias

Arrhythmias may be seen on 12-lead ECGs or on strips of one or more leads. Some arrhythmias are obvious at first glance and don't require intense analysis. Others, however, are more fun! They require detective work, i.e., logical thinking based on a knowledge of cardiac electrophysiology. The analysis should begin with identifying characteristics of impulse formation (if known) as well as impulse conduction. Here are some things to think about:

• Descriptors of impulse formation (i.e. the pacemaker)
• Descriptors of impulse conduction (i.e., how it moves through the heart)

Descriptors of impulse formation

(i.e. the pacemaker or region of impulse formation)

• Site of origin (i.e., where is the abnormal rhythm coming from?)
  • Sinus Node (e.g., sinus tachycardia)
  • Atria (e.g., PAC)
  • AV junction (e.g., junctional escape rhythm)
  • Ventricles (e.g., PVC)
• Rate (i.e., relative to the "expected rate" for that pacemaker location)
  • Accelerated - faster than expected (e.g., accelerated junctional rhythm @ 75bpm)
  • Slower than expected (e.g., marked sinus bradycardia @ 40bpm)
  • Normal (e.g., junctional escape rhythm)
• Regularity of ventricular or atrial response
  • Regular (e.g., PSVT)
  • Regular irregularity (e.g., ventricular bigeminy)
  • Irregular irregularity (e.g., atrial fibrillation or MAT)
  • Irregular (e.g., multifocal PVCs)
• Onset (i.e., how does the arrhythmia begin?)
  • Active onset (i.e., begins prematurely as with PAC or PVC)
  • Passive onset (e.g., ventricular escape beat or rhythm)

Descriptors of impulse conduction

(i.e., how abnormal rhythm conducts through the heart)

• Antegrade (forward) vs. retrograde (backward) conduction
• Conduction delays or blocks: i.e., 1st, 2nd (type I or II), 3rd degree blocks
• Sites of potential conduction delay
  • Sino-Atrial (SA) exit block (can only recognize 2nd degree SA block on ECG)
  • ntra-atrial delay (usually not recognized)
  • AV conduction delays (common)
  • IV blocks (e.g., bundle branch or fascicular blocks)

Now let's explore some real rhythm abnormalities..... (Return to Lesson 5)