Non-Sinus

P wave morphology is not consistent with sinus (including inverted P in lead I)
Normal Rate:
  1. Ectopic atrial rhythm 
  2. Dextrocardia 
  3. Limb lead reversal
  4. Retrograde P waves
  5. Artifact
Multiple P wave morphologies
  1. Wandering atrial pacemaker
Fast Rate:
  1. Ectopic Atrial Tachycardia
  2. Atrial Flutter
Multiple P wave morphologies
  1. ​Multifocal atrial tachycardia

Ectopic Atrial Rhythm

  • P waves are abnormal in both limb leads and chest leads
CLINICAL SIGNIFICANCE
  • Not much
  • No treatment is necessary
  • Rarely associated with atrial tachycardia
DEXTROCARDIA
  • Both P and QRS are inverted in lead I
  • QRS progression is reversed in chest leads
CLINICAL SIGNIFICANCE
  • ECG is not interpretable and may mimic MIs, fascicular blocks, ischemia
  • Repeat ECG with everything reversed
LIMB LEAD REVERSAL
  • P waves are normal in the chest leads
  • QRS may be inverted in lead I
  • Lead II may look like a flat line
CLINICAL SIGNIFICANCE
  • Must repeat the ECG!
  • Limb leads are bipolar leads
  • Limb lead reversal may mimic and mask MIs, fascicular blocks, low voltage, hypertrophy, ischemia
  • Lead reversals are very common

Retrograde P waves

  • P waves follow the QRS complexes
  • P waves have “retrograde morphology”
    • negative in II, III, aVF
    • usually upright in V1
  • Following junctional QRS complexes
    • junctional rhythm or junctional tachycardia
  • Following ventricular QRS complexes
    • idioventricular rhythm or VT
  • Following ventricular paced complexes
CLINICAL SIGNIFICANCE
  • When you see an obvious narrow-QRS tachycardia but the computer “thinks” it is a wide-complex tachycardia:
    • It is almost always reentrant PSVT where the retrograde P waves are measured as if they were part of the QRS complexes
  • Pacemaker Syndrome
    • Chest discomfort, shortness of breath related to abnormal pacemaker syndrome
    • Most common in ventricular pacing with 1:1 retrograde conduction
    • Neck veins: “cannon JVPs”
    • Left atrium: “cannon PVPs” (cannot see)
    • Either due to ventricular pacer or A-V pacemaker with atrial lead malfunction
    • Treatment: upgrade the pacemaker

Artifact

  • Parkinsonian tremor
  • High frequency oscillatory ventilation
  • Both are typically 5 Hz artifacts
  • 5 Hz = 300/min which is the usual atrial rate in atrial flutter
  • Clues for distinguishing artifact from flutter: 
    • Flutter waves are typically sharp
    •  Flutter waves are typically negative in II, III, aVF
    • Sinus P waves are present
CLINICAL SIGNIFICANCE
  • Parkinsonian tremor and HFOV are frequently mistaken for Atrial Flutter
  • Inappropriate treatments including electric cardioversion have been described

Ectopic Atrial Tachycardia

  • Atrial rate 110-220
  • P wave morphology is abnormal in the limb leads and the chest leads
CLINICAL SIGNIFICANCE
  • Usually a marker of “sickness”
  • Usually does not require treatment
    • difficult to suppress
    • ventricular rate equals atrial rate
  • Anticoagulation is usually not indicated

​Atrial Flutter

  • Atrial rate 230-380
  • Extremely common arrhythmia in sick hospitalized patients
  • Flutter waves are typically sharp and negative in leads II, III and aVF
  • Flutter waves are typically upright in V1
  • Atrial Flutter with 2:1 conduction is the most common regular SVT outside of sinus tachycardia in hospitalized patients

atrial flutter red flags

Frequently missed by the interpretation software and by physicians
​Think about atrial flutter if the computer read out says;
  1. Sinus tachycardia with 1st degree AV block
  2. Sinus tachycardia with short PR
  3. Ectopic Atrial tachycardia
  4. Sinus tachycardia with Vector 

Multiple P Wave MOrphologies with Variable PR Intervals

  • Rate <100: wandering atrial pacemaker
  • Rate >100: multifocal atrial tachycardia
    • Frequently read as atrial fibrillation
    • Frequently associated with decompensated lung disease, critical illness, postoperative state
    • No anticoagulation, no digoxin, no cardioversion
    • May treat with diltiazem or beta blocker if symptomatic
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