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 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), Digoxin.

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 wave pattern
Patient has no palpable pulse
Treatment: Defibrillation, epinephrine, amiodarone, lidocaine HCl