ACLS — Advanced Cardiovascular Life Support — All Questions

Which pair of rhythms is treated with defibrillation (i.e., is 'shockable')?

• a.Asystole and pulseless electrical activity (PEA)
• b.Ventricular fibrillation and pulseless ventricular tachycardia✓
• c.Sinus bradycardia and first-degree AV block
• d.Normal sinus rhythm and atrial flutter with a pulse

Only ventricular fibrillation (VF) and pulseless ventricular tachycardia (pVT) are shockable — defibrillation can reset the chaotic ventricular activity so an organized rhythm can resume. Asystole and PEA are non-shockable; they are treated with CPR, epinephrine, and correction of reversible causes. Delivering a shock to asystole or PEA provides no benefit.

The monitor shows a flat line, confirmed in two leads, in a pulseless patient. The correct action is to:

• a.Defibrillate immediately
• b.Perform synchronized cardioversion
• c.CPR and epinephrine; no shock✓
• d.Give adenosine 6 mg rapid IV push

Asystole is a nonshockable rhythm: continue high-quality CPR, give epinephrine as early as possible, and look for reversible causes. Shocks and cardioversion do not treat asystole.

A stable patient has a regular narrow-complex tachycardia at 180 bpm; vagal maneuvers have not worked. The next appropriate step is:

• a.Defibrillate the patient
• b.Give adenosine 6 mg by rapid IV push✓
• c.Give atropine 1 mg IV
• d.Give epinephrine 1 mg IV push

A regular narrow-complex tachycardia that persists after vagal maneuvers in a stable patient is treated with adenosine 6 mg rapid IV push (then 12 mg if needed). This most likely represents a re-entrant SVT, and adenosine's transient AV nodal block can break the circuit. Defibrillation, atropine, and arrest-dose epinephrine are all inappropriate for a stable, perfusing SVT.

Which rhythm pair is treated with defibrillation?

• a.Sinus bradycardia and first-degree block
• b.Atrial flutter and sinus tachycardia
• c.Asystole and PEA
• d.VF and pulseless VT✓

Defibrillation is the definitive treatment for VF and pulseless VT; asystole and PEA are nonshockable.

The monitor shows an organized rhythm, but there is no pulse. What is this called?

• a.Pulseless electrical activity✓
• b.Ventricular fibrillation
• c.Sinus rhythm with ROSC
• d.Atrial fibrillation

An organized rhythm without a pulse is PEA, a nonshockable arrest rhythm treated with CPR, epinephrine and a search for reversible causes.

How is wide-complex tachycardia defined in the 2025 Guidelines?

• a.Over 150/min, QRS ≥0.12 s✓
• b.Over 100/min with QRS under 0.08 s
• c.Any irregular rhythm
• d.Under 60/min with a wide QRS

Wide-complex tachycardia is generally defined as a rhythm greater than 150/min with a QRS duration of 0.12 second or more.

What distinguishes polymorphic VT from monomorphic VT?

• a.The rate is always under 100
• b.P waves precede every QRS
• c.QRS shape changes beat to beat✓
• d.The QRS is narrow

Polymorphic VT is a wide-complex tachycardia of ventricular origin with differing QRS configurations from beat to beat.

Torsades de pointes is associated with which baseline ECG finding?

• a.A short PR interval
• b.A prolonged QTc✓
• c.A narrow QRS complex
• d.ST elevation in two leads

Torsades is a form of polymorphic VT associated with a prolonged corrected QT; risk rises when QTc exceeds 500 ms with bradycardia.

Which narrow-complex tachycardias do the Guidelines list?

• a.VF and pulseless VT only
• b.Asystole and PEA
• c.Complete heart block only
• d.Sinus tachycardia, flutter, AVNRT and AVRT✓

Narrow-complex tachycardias include sinus tachycardia, atrial flutter, AV nodal reentrant tachycardia, AV reentrant tachycardia and other atrial tachycardias.

How do the Guidelines describe atrial fibrillation?

• a.A normal variant in athletes
• b.A chaotic rhythm from many circuits✓
• c.A single organized atrial circuit
• d.A ventricular rhythm with no P waves

Atrial fibrillation is a disorganized atrial rhythm due to multiple reentry circuits, while atrial flutter is a more organized rhythm from a single macroreentrant circuit.

What heart rate threshold did the 2018 bradycardia guideline adopt?

• a.Under 40/min
• b.Under 50/min✓
• c.Under 70/min
• d.Under 30/min

Bradycardia was historically defined as under 60/min, but the 2018 ACC/AHA/HRS guideline adopted a threshold of under 50/min.

A wide-complex tachycardia can be supraventricular in origin. Which mechanism can cause this?

• a.Sinus arrhythmia
• b.Bundle branch block✓
• c.First-degree AV block
• d.Hypothermia alone

A wide QRS can arise from ventricular conduction, bundle branch block, conduction through a bypass tract, or ventricular pacing.

Adenosine is given to a stable patient with a regular narrow tachycardia, and flutter waves appear briefly. What did adenosine do?

• a.It converted the rhythm to VF
• b.It had no effect on conduction
• c.It blocked the AV node✓
• d.It caused atrial fibrillation permanently

Adenosine blocks the AV node, which can confirm a diagnosis of atrial flutter or fibrillation by revealing the underlying atrial activity.

Why must polymorphic VT be shocked unsynchronized?

• a.Its QRS varies too much to sync✓
• b.Synchronized shocks are always weaker
• c.Synchronization is only for children
• d.It is always pulseless

Polymorphic VT cannot be synchronized reliably because each QRS differs, so it requires a high-energy unsynchronized shock.

What is the concern when atrial fibrillation or flutter has lasted more than 48 hours without anticoagulation?

• a.The rhythm is always VT
• b.Risk of thromboembolism✓
• c.Adenosine will convert it
• d.Rate control is impossible

Converting AF or flutter present for more than 48 hours in patients who are not anticoagulated risks thromboembolic events.

Why does a narrow-complex tachycardia in a septic patient need careful interpretation?

• a.It may be a response✓
• b.It must be shocked at once
• c.It cannot occur with fever
• d.It is always VT in disguise

There must be a reasonable expectation that a narrow-complex tachycardia is causing instability rather than being a manifestation of another illness such as sepsis.

What proportion of narrow-complex tachycardias may be converted with vagal maneuvers, drugs, or both?

• a.None
• b.About 25%
• c.About 5%
• d.Up to 98%✓

Most patients with narrow-complex tachycardia have conversion success rates of up to 98% with vagal maneuvers, pharmacological treatment, or both.