ACLS Rhythms and Interpretation

STEP 1: RECAP THE PQRST PROPERTIES

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	End 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 Bradycardia

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

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)

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)

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 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

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

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

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 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).

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

Pulseless Ventricular Fibrillation (vFib)

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