ACLS Rhythm Review 2025–2026 | 20 Basic Cardiac Rhythms to Memorize, ECG Interpretation, Practice Questions & Exam Prep

ACLS RHYTHM REVIEW 2025 2026 20
BASIC CARDIAC RHYTHMS TO MEMORIZE
ECG INTERPRETATION PRACTICE
QUESTIONS and EXAM PREP

ACLS Rhythm Review & Clinical Management
(Questions 1–150)
1. You observe a regular cardiac rhythm under 60 beats
per minute with a constant PR interval and a single,
uniform P wave preceding every narrow QRS complex.
What is this basic rhythm?
A. Ventricular Fibrillation
B. Sinus Bradycardia
C. First-Degree AV Block
D. Type II Second-Degree AV Block
 Correct Answer: B. Sinus Bradycardia
 Rationale: Sinus bradycardia meets all the criteria of normal
sinus rhythm (regularity, uniform upright P waves in lead II,
constant PR interval) but features a discharge rate of less than
60 beats per minute.
2. A patient presents with symptomatic Sinus
Bradycardia (HR 42 bpm), a blood pressure of 80/40
mmHg, and altered mental status. According to the
ACLS Bradycardia Algorithm, what is the first-line
medication intervention?
A. Amiodarone 150 mg IV bolus
B. Adenosine 6 mg rapid IV push
C. Atropine 1 mg IV push
D. Epinephrine 1 mg IV push
 Correct Answer: C. Atropine 1 mg IV push

, Rationale: For symptomatic, unstable bradycardia, Atropine 1
mg IV push is the primary first-line pharmacological
intervention. It can be repeated every 3 to 5 minutes to a
maximum total dose of 3 mg. Adenosine is for SVT, Amiodarone
is for tachyarrhythmias, and Epinephrine 1 mg IV is reserved for
pulseless cardiac arrest.
3. What is the maximum cumulative dose of Atropine
that can be administered to an adult patient during the
management of symptomatic bradycardia?
A. 1 mg
B. 1.5 mg
C. 3 mg
D. 6 mg
 Correct Answer: C. 3 mg
 Rationale: The single dose of Atropine is 1 mg. This may be
repeated every 3–5 minutes up to a maximum cumulative dose
of 3 mg, which represents full vagal blockade. Doses beyond this
are unlikely to yield further clinical benefits.
4. If Atropine fails to stabilize an unstable, symptomatic
bradycardia patient, what non-pharmacological
electrical intervention should be initiated immediately?
A. Synchronized Cardioversion at 100 Joules
B. Transcutaneous Pacing (TCP)
C. Unsynchronized Defibrillation at 200 Joules
D. Immediate Carotid Sinus Massage
 Correct Answer: B. Transcutaneous Pacing (TCP)
 Rationale: If atropine is ineffective, the ACLS bradycardia
algorithm directs providers to immediately initiate
transcutaneous pacing (TCP), or begin an inotropic infusion
(epinephrine or dopamine). Cardioversion is for unstable
tachycardia, and defibrillation is for pulseless rhythms.

, 5. When setting up a transcutaneous pacemaker (TCP)
for a symptomatic bradycardia patient, what parameters
must the ACLS provider adjust to achieve electrical and
mechanical capture?
A. Pacing rate (usually 60–80 bpm) and current output
(milliamperes, mA)
B. Synchronizer mode button and energy level in Joules
C. The default pulse width duration and chest lead configurations
D. Internal defibrillation thresholds and baseline impedance
settings
 Correct Answer: A. Pacing rate (usually 60–80 bpm)
and current output (milliamperes, mA)
 Rationale: To pace a patient, the provider sets the desired
demand pacing rate (typically 60–80 beats per minute) and
slowly turns up the current output in milliamperes (mA) until a
pacing spike is consistently followed by a wide QRS complex
(electrical capture) and an accompanying peripheral pulse is felt
(mechanical capture).
6. What cardiac rhythm is characterized by a regular
rate over 100 beats per minute with uniform P waves, a
constant PR interval, and narrow QRS complexes?
A. Atrial Fibrillation
B. Sinus Tachycardia
C. Supraventricular Tachycardia (SVT)
D. Ventricular Tachycardia
 Correct Answer: B. Sinus Tachycardia
 Rationale: Sinus tachycardia exhibits normal sinus
characteristics but features a rate exceeding 100 beats per
minute, typically maxing out around 150–160 bpm in resting
adults. It is almost always a secondary compensatory response
to an underlying cause like pain, fever, hypovolemia, or hypoxia.

, 7. What is the primary clinical focus when managing a
patient in Sinus Tachycardia?
A. Administering an immediate rapid IV push of Adenosine
B. Performing immediate synchronized cardioversion at
maximum energy
C. Identifying and treating the underlying causative
factor (e.g., fluid resuscitation for hypovolemia)
D. Delivering a precordial thump to reset the sinus node
 Correct Answer: C. Identifying and treating the
underlying causative factor (e.g., fluid resuscitation for
hypovolemia)
 Rationale: Sinus tachycardia is an adaptive, physiological
mechanism. Slowing the rate with electricity or medications
without addressing the cause (such as dehydrating a patient in
hypovolemic shock) can lead to hemodynamic collapse.
Treatment must target the underlying trigger.
8. You observe a regular, narrow-complex tachycardia
under 150 beats per minute with P waves buried within
or immediately following the QRS, starting and stopping
abruptly. This is clinically identified as:
A. Normal Sinus Rhythm
B. Atrial Flutter
C. Supraventricular Tachycardia (SVT)
D. Polymorphic Ventricular Tachycardia
 Correct Answer: C. Supraventricular Tachycardia
(SVT)
 Rationale: SVT (often paroxysmal SVT or AVNRT) presents as
a rapid, regular, narrow-complex rhythm (usually 150–250
bpm) where individual P waves are often obscured or missing
because the electrical loop overrides the normal sinus
mechanism.