Cardiology Quiz: Ventricular Rhythms

ECG Rhythms Study Notes

• Ventricular Tachycardia (VTach):

  • Rapid ventricular rate (typically > 100-200 bpm)
  • Irregular QRS complexes with varying morphology
  • Atrial activity dissociated from ventricular activity
  • Typically wide, bizarre QRS complexes

• Idioventricular Rhythm:

  • Ventricular pacemaker takes over
  • Slow rate (20-40 bpm)
  • Wide, bizarre QRS complexes
  • No discernible P waves
  • Can be part of AV dissociation or third-degree heart block

• Premature Ventricular Contraction (PVC):

  • Premature ventricular activation
  • Wide, bizarre QRS complexes
  • No P wave preceding the PVC
  • Compensatory pause follows the PVC (usually)
  • Usually sporadic, but can be grouped (bigeminy, trigeminy)

• Ventricular Escape Beat:

  • Ventricle acts as a backup pacemaker
  • Slow rate
  • Wide, bizarre QRS complexes
  • No P waves preceding the beat
  • Non-compensatory pause follows

• Junctional Rhythm:

  • Originates in the AV node
  • Rate 40-60 bpm (faster than Idioventricular, slower than sinus)
  • Usually regular
  • P wave may be absent, antegrade (before QRS), or retrograde (after QRS)
  • PR interval variable - can be absent if retrograde or very short if antegrade; PR interval does not represent atrial stimulation

• Junctional Tachycardia:

  • Junctional rhythm with rate over 100 bpm
  • Typically regular
  • P wave may be absent, antegrade, or retrograde
  • PR interval variable

• Premature Junctional Contraction (PJC):

  • Premature activation from the AV node
  • Identical QRS complex morphology as underlying rhythm
  • No P wave or P wave different from underlying rhythm
  • Can occur in sporadic or grouped patterns

• Escape Beat:

  • Occurs when regular pacemaker fails
  • Rate depends on the underlying rhythm
  • Longer than normal P-P interval
  • A variety of ECG appearances

Atrial Rhythms

• Atrial Flutter:

  • Rapid atrial rate (usually 250-350 bpm)
  • Regular or sometimes variable rate of the ventricles
  • "Saw-toothed" F waves
  • Commonly 2:1 block (2 F waves for every QRS) ,but varies

• Atrial Fibrillation (Afib):

  • Chaotic atrial activity; no clear P waves
  • Irregularly irregular rhythm
  • Ventricular rate varies
  • No discernible P waves or rhythm
  • Random QRS intervals

• Wandering Atrial Pacemaker (WAP):

  • Multiple atrial foci pace the heart
  • Irregularly irregular rhythm
  • At least 3 different P wave morphologies
  • Variable PR intervals

• Multifocal Atrial Tachycardia (MAT):

  • Tachycardic form of WAP
  • Irregularly irregular with at least 3 different P wave morphologies
  • More frequent than WAP & often seen with lung disease.

• Premature Atrial Contraction (PAC):

  • Premature activation of an atrial pacemaker
  • May have a different P wave morphology
  • Noncompensatory pause follows
  • Underlying rhythm continues after the PAC

• Ectopic Atrial Tachycardia (EAT):

  • Ectopic atrial focus paces the heart
  • Typically over 100 beats per minute
  • Regular rate
  • P wave with different morphology from sinus rhythm
  • PR interval is specific and varies from underlying rate

• Sinus Pause/Arrest:

  • Temporary cessation of SA nodal firing
  • Paused sinus rhythm and then continuation
  • Irregular rhythm with dropped beats

• Sinus Block:

  • SA node fails to conduct some beats
  • Irregular rhythm with dropped beats at specific intervals
  • Underlying rhythm resumes on time

• Sinus Bradycardia:

  • Slow sinus rate (less than 60 bpm)
  • Regular rhythm
  • Normal P waves, but slow

• Sinus Tachycardia:

  • Fast sinus rate (over 100 bpm)
  • Regular rhythm
  • Normal P waves

• Normal Sinus Rhythm (NSR):

  • SA node is the pacemaker
  • Regular rhythm, 60-100 bpm
  • Presence of consistent P-QRS-T formations
  • Intervals within normal range

• Respiratory Sinus Arrhythmia:

  • Rate varies with respiration
  • Regularity changes with breathing
  • Slower on exhalation, faster on inhalation
  • PP intervals are the only ones varying with respiration