SCST-D1 SCST Diploma in ECG Interpretation
Exam 2026–2027 | Verified Questions &
Correct Answers with Detailed Explanations
| Latest ECG Certification Prep PDF
• This document contains 200 verified ECG interpretation exam questions with
correct answers and detailed EXPERT RATIONALE, designed to prepare you for the
SCST Diploma in ECG Interpretation certification.
• Study by reading each question carefully, attempting your answer before
revealing the correct option — the bolded answer and EXPERT RATIONALE below
each question reinforce clinical understanding and exam confidence.
SCST DIPLOMA IN ECG INTERPRETATION EXAM 2026–2027 200 Verified
Questions | Correct Answers | Detailed EXPERT RATIONALE
SECTION 1: BASIC ELECTROPHYSIOLOGY
1. What does the P wave represent on an ECG?
A. Ventricular depolarization
B. Ventricular repolarization
C. Atrial depolarization
D. Atrioventricular conduction delay
E. Septal depolarization
Correct Answer: C. Atrial depolarization
EXPERT RATIONALE: The P wave represents the electrical depolarization of
both atria, which triggers atrial contraction. It normally precedes the QRS complex
and should be upright in leads I, II, and aVF.
2. What does the QRS complex represent?
,A. Atrial repolarization
B. Atrial depolarization
C. Ventricular repolarization
D. Ventricular depolarization
E. SA node firing
Correct Answer: D. Ventricular depolarization
EXPERT RATIONALE: The QRS complex represents the rapid depolarization of
both ventricles. Its normal duration is 0.06–0.10 seconds (less than 3 small
squares). Prolongation suggests bundle branch block or ventricular rhythm.
3. What does the T wave represent?
A. Atrial depolarization
B. Ventricular depolarization
C. Atrial repolarization
D. Ventricular repolarization
E. Bundle of His activation
Correct Answer: D. Ventricular repolarization
EXPERT RATIONALE: The T wave reflects ventricular repolarization, i.e., the
recovery phase of ventricular muscle. It is normally upright in most leads except
aVR and V1.
4. What is the normal duration of the PR interval?
A. 0.06–0.10 seconds
B. 0.12–0.20 seconds
C. 0.20–0.30 seconds
,D. 0.08–0.12 seconds
E. 0.30–0.40 seconds
Correct Answer: B. 0.12–0.20 seconds
EXPERT RATIONALE: The PR interval measures from the start of the P wave to
the start of the QRS. It reflects conduction through the AV node and His-Purkinje
system. A value above 0.20 seconds indicates first-degree heart block.
5. What is the normal QRS duration?
A. 0.20–0.30 seconds
B. 0.30–0.40 seconds
C. Less than 0.12 seconds
D. 0.12–0.20 seconds
E. Greater than 0.20 seconds
Correct Answer: C. Less than 0.12 seconds
EXPERT RATIONALE: A normal QRS complex lasts less than 120ms (3 small
squares at standard speed). A QRS ≥0.12 seconds is abnormally wide and suggests
bundle branch block, ventricular ectopy, or accessory pathway conduction.
6. The SA node is the primary pacemaker of the heart. What is its normal
firing rate?
A. 20–40 bpm
B. 40–60 bpm
C. 60–100 bpm
D. 100–150 bpm
E. 150–200 bpm
, Correct Answer: C. 60–100 bpm
EXPERT RATIONALE: The SA node (sinoatrial node) is located in the right atrium
and spontaneously fires at 60–100 bpm under normal conditions. It dominates
other potential pacemakers due to its faster intrinsic rate.
7. What is the intrinsic rate of the AV node?
A. 60–100 bpm
B. 20–40 bpm
C. 40–60 bpm
D. 100–120 bpm
E. 10–20 bpm
Correct Answer: C. 40–60 bpm
EXPERT RATIONALE: The AV node can act as a secondary pacemaker with an
intrinsic rate of 40–60 bpm. It takes over pacemaker function if the SA node fails or
its impulses are blocked.
8. What is the intrinsic rate of ventricular pacemaker cells (Purkinje fibers)?
A. 60–100 bpm
B. 40–60 bpm
C. 100–150 bpm
D. 20–40 bpm
E. 80–100 bpm
Correct Answer: D. 20–40 bpm
EXPERT RATIONALE: Purkinje fibers and ventricular myocardium have the
slowest intrinsic pacemaker rate of 20–40 bpm. They represent the last line of
pacemaker backup and produce wide, bizarre QRS complexes when they take over.
Exam 2026–2027 | Verified Questions &
Correct Answers with Detailed Explanations
| Latest ECG Certification Prep PDF
• This document contains 200 verified ECG interpretation exam questions with
correct answers and detailed EXPERT RATIONALE, designed to prepare you for the
SCST Diploma in ECG Interpretation certification.
• Study by reading each question carefully, attempting your answer before
revealing the correct option — the bolded answer and EXPERT RATIONALE below
each question reinforce clinical understanding and exam confidence.
SCST DIPLOMA IN ECG INTERPRETATION EXAM 2026–2027 200 Verified
Questions | Correct Answers | Detailed EXPERT RATIONALE
SECTION 1: BASIC ELECTROPHYSIOLOGY
1. What does the P wave represent on an ECG?
A. Ventricular depolarization
B. Ventricular repolarization
C. Atrial depolarization
D. Atrioventricular conduction delay
E. Septal depolarization
Correct Answer: C. Atrial depolarization
EXPERT RATIONALE: The P wave represents the electrical depolarization of
both atria, which triggers atrial contraction. It normally precedes the QRS complex
and should be upright in leads I, II, and aVF.
2. What does the QRS complex represent?
,A. Atrial repolarization
B. Atrial depolarization
C. Ventricular repolarization
D. Ventricular depolarization
E. SA node firing
Correct Answer: D. Ventricular depolarization
EXPERT RATIONALE: The QRS complex represents the rapid depolarization of
both ventricles. Its normal duration is 0.06–0.10 seconds (less than 3 small
squares). Prolongation suggests bundle branch block or ventricular rhythm.
3. What does the T wave represent?
A. Atrial depolarization
B. Ventricular depolarization
C. Atrial repolarization
D. Ventricular repolarization
E. Bundle of His activation
Correct Answer: D. Ventricular repolarization
EXPERT RATIONALE: The T wave reflects ventricular repolarization, i.e., the
recovery phase of ventricular muscle. It is normally upright in most leads except
aVR and V1.
4. What is the normal duration of the PR interval?
A. 0.06–0.10 seconds
B. 0.12–0.20 seconds
C. 0.20–0.30 seconds
,D. 0.08–0.12 seconds
E. 0.30–0.40 seconds
Correct Answer: B. 0.12–0.20 seconds
EXPERT RATIONALE: The PR interval measures from the start of the P wave to
the start of the QRS. It reflects conduction through the AV node and His-Purkinje
system. A value above 0.20 seconds indicates first-degree heart block.
5. What is the normal QRS duration?
A. 0.20–0.30 seconds
B. 0.30–0.40 seconds
C. Less than 0.12 seconds
D. 0.12–0.20 seconds
E. Greater than 0.20 seconds
Correct Answer: C. Less than 0.12 seconds
EXPERT RATIONALE: A normal QRS complex lasts less than 120ms (3 small
squares at standard speed). A QRS ≥0.12 seconds is abnormally wide and suggests
bundle branch block, ventricular ectopy, or accessory pathway conduction.
6. The SA node is the primary pacemaker of the heart. What is its normal
firing rate?
A. 20–40 bpm
B. 40–60 bpm
C. 60–100 bpm
D. 100–150 bpm
E. 150–200 bpm
, Correct Answer: C. 60–100 bpm
EXPERT RATIONALE: The SA node (sinoatrial node) is located in the right atrium
and spontaneously fires at 60–100 bpm under normal conditions. It dominates
other potential pacemakers due to its faster intrinsic rate.
7. What is the intrinsic rate of the AV node?
A. 60–100 bpm
B. 20–40 bpm
C. 40–60 bpm
D. 100–120 bpm
E. 10–20 bpm
Correct Answer: C. 40–60 bpm
EXPERT RATIONALE: The AV node can act as a secondary pacemaker with an
intrinsic rate of 40–60 bpm. It takes over pacemaker function if the SA node fails or
its impulses are blocked.
8. What is the intrinsic rate of ventricular pacemaker cells (Purkinje fibers)?
A. 60–100 bpm
B. 40–60 bpm
C. 100–150 bpm
D. 20–40 bpm
E. 80–100 bpm
Correct Answer: D. 20–40 bpm
EXPERT RATIONALE: Purkinje fibers and ventricular myocardium have the
slowest intrinsic pacemaker rate of 20–40 bpm. They represent the last line of
pacemaker backup and produce wide, bizarre QRS complexes when they take over.
