Page 1 of 51
Cardiac Rhythms & Dysrhythmias
Overview | 2026 Updated Guide with
complete solutions.
1. What is the normal heart rate range for sinus rhythm in an
adult?
a) 40–60 bpm
b) 60–100 bpm
c) 80–120 bpm
d) 100–150 bpm
Answer: b) 60–100 bpm
Rationale: Normal sinus rhythm (NSR) originates from the SA node
at a rate of 60–100 bpm. Rates <60 are sinus bradycardia; >100
are sinus tachycardia.
,Page 2 of 51
2. On an ECG strip, the P wave represents:
a) Ventricular depolarization
b) Atrial depolarization
c) Ventricular repolarization
d) AV node conduction delay
Answer: b) Atrial depolarization
Rationale: The P wave reflects electrical activation of the atria
(sinoatrial node to atria). QRS = ventricular depolarization; T
wave = ventricular repolarization.
3. The PR interval should normally last:
a) <0.12 seconds
b) 0.12–0.20 seconds
c) 0.20–0.32 seconds
d) >0.40 seconds
Answer: b) 0.12–0.20 seconds (3–5 small boxes)
*Rationale: PR interval measures atrial depolarization plus AV
,Page 3 of 51
nodal delay. Prolonged >0.20 seconds suggests first-degree AV
block.*
4. Which lead is considered the “rhythm strip” for continuous
monitoring?
a) Lead I
b) Lead II
c) Lead V1
d) Lead aVF
Answer: b) Lead II
Rationale: Lead II provides the most upright P wave and is
standard for rhythm analysis. It best visualizes atrial activity.
5. A patient has a regular rhythm, rate 88 bpm, one P wave
before each QRS, PR 0.16 sec, QRS 0.08 sec. The
interpretation is:
a) Sinus arrhythmia
b) Normal sinus rhythm
, Page 4 of 51
c) Sinus tachycardia
d) First-degree AV block
Answer: b) Normal sinus rhythm
*Rationale: All criteria for NSR are met: rate 60-100, regular, P
before each QRS, normal PR and QRS duration.*
(Continue this pattern for all 20 basic ECG questions. Here are a
few more:)
6. The QT interval is corrected for heart rate using which
formula?
a) Bazett’s formula
b) Cockcroft-Gault
c) Parkland formula
d) CURB-65
Answer: a) Bazett’s formula (QTc = QT / √RR)
Rationale: QTc prolongation >450 ms in men, >470 ms in women
increases risk of torsades de pointes.
Cardiac Rhythms & Dysrhythmias
Overview | 2026 Updated Guide with
complete solutions.
1. What is the normal heart rate range for sinus rhythm in an
adult?
a) 40–60 bpm
b) 60–100 bpm
c) 80–120 bpm
d) 100–150 bpm
Answer: b) 60–100 bpm
Rationale: Normal sinus rhythm (NSR) originates from the SA node
at a rate of 60–100 bpm. Rates <60 are sinus bradycardia; >100
are sinus tachycardia.
,Page 2 of 51
2. On an ECG strip, the P wave represents:
a) Ventricular depolarization
b) Atrial depolarization
c) Ventricular repolarization
d) AV node conduction delay
Answer: b) Atrial depolarization
Rationale: The P wave reflects electrical activation of the atria
(sinoatrial node to atria). QRS = ventricular depolarization; T
wave = ventricular repolarization.
3. The PR interval should normally last:
a) <0.12 seconds
b) 0.12–0.20 seconds
c) 0.20–0.32 seconds
d) >0.40 seconds
Answer: b) 0.12–0.20 seconds (3–5 small boxes)
*Rationale: PR interval measures atrial depolarization plus AV
,Page 3 of 51
nodal delay. Prolonged >0.20 seconds suggests first-degree AV
block.*
4. Which lead is considered the “rhythm strip” for continuous
monitoring?
a) Lead I
b) Lead II
c) Lead V1
d) Lead aVF
Answer: b) Lead II
Rationale: Lead II provides the most upright P wave and is
standard for rhythm analysis. It best visualizes atrial activity.
5. A patient has a regular rhythm, rate 88 bpm, one P wave
before each QRS, PR 0.16 sec, QRS 0.08 sec. The
interpretation is:
a) Sinus arrhythmia
b) Normal sinus rhythm
, Page 4 of 51
c) Sinus tachycardia
d) First-degree AV block
Answer: b) Normal sinus rhythm
*Rationale: All criteria for NSR are met: rate 60-100, regular, P
before each QRS, normal PR and QRS duration.*
(Continue this pattern for all 20 basic ECG questions. Here are a
few more:)
6. The QT interval is corrected for heart rate using which
formula?
a) Bazett’s formula
b) Cockcroft-Gault
c) Parkland formula
d) CURB-65
Answer: a) Bazett’s formula (QTc = QT / √RR)
Rationale: QTc prolongation >450 ms in men, >470 ms in women
increases risk of torsades de pointes.
