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ACLS Rhythms and Interpretation

STEP 1: RECAP THE PQRST PROPERTIES

PQRST Wave

Figure 8b

PROTOTYPICAL ECG TRACING
P-wave Electrical activity is traveling through the atria.
Synonymous with atrial depolarization.
Reflects atrial contraction.
QRS
Complex		 Electrical activity is traveling through the ventricles.
Depolarization of the left and right ventricles.
Reflects ventricular contraction.
T-wave Synonymous with ventricular repolarization.
Reflects the start of ventricular relaxation.
PR Interval Onset of the P-wave to the start of the QRS complex.
Reflects conduction through the atrioventricular (AV) node.
PR Segment End of the P-wave to the start of the QRS complex.
Reflects time delay between atrial and ventricular activation.
ST Interval Onset of the S-wave to the start of the T-wave.
Reflects initial, slow phase of ventricular repolarization.
ST Segment End of the S-wave (J point) to the start of the T-wave.
Reflects ventricular repolarization.
QT Interval Onset of the QRS complex to the end of the T-wave.
Reflects the period between ventricular depolarization and ventricular repolarization.
TP Interval Onset of the T wave to the end of the P-wave.
Reflects a period of electrical inactivity.
RR Interval Reflects time elapsed between two successive R-waves of the QRS.

STEP 2: IDENTIFY THE COMMON CATEGORIES OF ACLS RHYTHMS
WITH A FEW EXAMPLES

Sinus rhythms:

  • Normal sinus rhythm (NSR)
  • Sinus bradycardia
  • Sinus tachycardia

Bradyarrhythmia and Conduction Blocks:

  • 1st degree AV block
  • 2nd degree AV block Type I (Mobitz Type I, Wenckebach’s)
  • 2nd degree AV block Type II (Mobitz Type II)
  • 3rd degree AV block (complete heart block, CHB)

Tachyarrhythmias:

  • Supraventricular tachycardia (SVT)
  • Wide-complex tachycardias

Pulseless rhythms:

  • Pulseless ventricular tachycardia (vTach)
  • Ventricular fibrillation (vFib)
  • Pulseless electrical activity (PEA)
  • Asystole

Atrial Dysrhythmias:

  • Atrial flutter
  • Atrial fibrillation (aFib)

STEP 3: IDENTIFY THE MOST COMMON ACLS RHYTHMS

Normal Sinus Rhythm (NSR)

  • Normal P-wave
  • Normal QRS Complex
  • Normal T-wave
  • HR: 60-100 BPM (at rest)
  • Treatment: None

Sinus Rythm

Sinus Bradycardia

  • Normal P-wave
  • Normal QRS Complex
  • Normal T-wave
  • HR: <60 BPM (at rest)
  • Treatment (Symptomatic): Atropine, Dopamine (infusion), Epinephrine (infusion)

Sinus Bradycardia Rythm

Sinus Tachycardia

  • Normal P-wave
  • Normal QRS Complex
  • Normal T-wave
  • HR: >100 BPM (at rest)
  • Treatment: Reverse underlying condition (fever, anxiety, exercise), beta-blockers (metoprolol, sotalol)

Sinus Tachycardia Rythm

1st Degree Heart Block

  • Prolonged PR interval due to delay in AV signal transmission
  • P-wave may be buried in the preceding T-wave
  • Treatment: Transcutaneous pacing (only indicated if prolongation of the PR interval is >400 ms)

1st degree AV block

2nd Degree AV block Type I (Mobitz Type I, Wenckebach’s)

  • Progressive lengthening of the PR interval
  • Progression occurs until the QRS complex is dropped
  • Treatment: Atropine, Dopamine, Transcutaneous pacing

2nd degree AV block Type I (Mobitz Type I, Wenckebach’s)

2nd Degree AV block Type II (Mobitz Type II)

  • PR interval is > 0.20 seconds and consistent (not gradually getting longer) but drops a beat, generally on a pattern of 3:1 or 4:1
  • Treatment: Transcutaneous pacing

2nd degree AV block Type II (Mobitz Type II)

3rd Degree AV block (complete heart block, CHB)

  • No identifiable relationship between the P-wave and QRS waves
  • P-P intervals are normal but do not relate to the QRS complex
  •  Treatment: Transcutaneous pacing

3rd degree AV block (complete heart block, CHB)

Supraventricular Tachycardia (SVT)

  • Profoundly rapid atrial rhythm with narrow QRS complexes
  • Occurs when the signal impulse originates over the bundle branches
  • HR: 150-250 BPM
  • Treatment: Vagal maneuvers, Adenosine, synchronized cardioversion

Supraventricular Tachycardia (SVT)

Atrial Fibrillation (aFib)

  • Uniquely characterized by an absence of P-waves before the QRS complex
  • HR: Highly irregular with significant fluctuation
  • Treatment: beta-blockers (Metoprolol, Sotalol, etc.), Ca++ channel blockers
    (Diltiazem, Verapamil, etc.), Digoxin, synchronized cardioversion.

Atrial Fibrillation (aFib)

Atrial Flutter

  • Uniquely characterized by a saw-toothed flutter appearance
  • Toothed fluttering represents multiple P-waves for a single QRS complex
  • Treatment: synchronized cardioversion, beta-blockers (Metoprolol, Sotalol, etc.),
    Ca++ channel blockers (Diltiazem, Verapamil, etc), Digoxin.

Atrial Flutter

Ventricular Tachycardia (vTach)

  • Abnormally-patterned wide QRS complex
  • No P-waves
  • High likelihood of rapid deterioration to a state of ventricular fibrillation
    (vFib)
  • Often responsive to electrical defibrillation
  • HR: >100 BPM
  • Treatment: Defibrillation

Ventricular Tachycardia (vTach)

Pulseless Ventricular Fibrillation (vFib)

  • Characterized by a chaotic wave pattern
  • Patient has no palpable pulse
  • Treatment: Defibrillation, epinephrine, amiodarone, lidocaine HCl

Pulseless Ventricular Fibrillation (vFib)

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