Nursing Foundation - ECG Detailed Notes With MCQs Practice

ECG Notes – Complete Electrocardiogram Guide for BSc Nursing & NORCET

ECG – Electrocardiogram is one of the most important cardiovascular diagnostic investigations used in nursing and clinical practice. An ECG records the electrical activity of the heart through electrodes placed on the patient's skin. It provides information about heart rate, rhythm, conduction, cardiac electrical activity and may show patterns associated with myocardial ischemia, infarction and other cardiac conditions. These notes cover ECG basics, waves, intervals, leads, electrode placement, normal values, ECG interpretation, arrhythmias, myocardial infarction changes, nursing responsibilities, ECG artifacts and exam-oriented MCQs.

This topic is especially useful for BSc Nursing, GNM Nursing, NORCET, AIIMS Nursing, NCLEX-RN, Staff Nurse and other nursing examinations.

Table of Contents

1. 1. What is ECG?
2. 2. Purpose and Uses of ECG
3. 3. Principle of ECG
4. 4. ECG Paper and Calibration
5. 5. ECG Waves
6. 6. ECG Intervals and Segments
7. 7. Normal ECG Values
8. 8. ECG Leads
9. 9. Limb Leads
10. 10. Chest Leads V1–V6
11. 11. ECG Electrode Placement
12. 12. ECG Recording Procedure
13. 13. Patient Preparation
14. 14. How to Calculate Heart Rate
15. 15. How to Assess Cardiac Rhythm
16. 16. Cardiac Axis
17. 17. Systematic ECG Interpretation
18. 18. Normal Sinus Rhythm
19. 19. Sinus Bradycardia
20. 20. Sinus Tachycardia
21. 21. Atrial Fibrillation
22. 22. Atrial Flutter
23. 23. Premature Ventricular Complex
24. 24. Ventricular Tachycardia
25. 25. Ventricular Fibrillation
26. 26. AV Blocks
27. 27. ECG Changes in Myocardial Infarction
28. 28. MI Lead Localization
29. 29. STEMI and ST Elevation
30. 30. ECG Artifacts
31. 31. Nursing Responsibilities
32. 32. ECG in Emergency Situations
33. 33. Documentation
34. 34. Common ECG Recording Errors
35. 35. Important NORCET Exam Points
36. 36. Frequently Asked Questions
37. 37. ECG MCQs Practice
38. 38. Answer Key with Explanations
39. 39. Quick Revision
40. 40. Clinical Updates
41. 41. Conclusion

1. What is ECG?

An electrocardiogram (ECG) is a graphical recording of the electrical activity of the heart over time.

The ECG machine detects electrical potentials generated by cardiac depolarization and repolarization and displays them as waves and intervals on ECG paper or a monitor.

Exam Definition: ECG is a graphic recording of the electrical activity of the heart obtained from electrodes placed on the body surface.

ECG vs EKG

ECG and EKG refer to the same test. "ECG" comes from the term electrocardiogram, while "EKG" is derived from the German spelling Elektrokardiogramm.

2. Purpose and Uses of ECG

An ECG may be used to:

• Determine heart rate.
• Assess cardiac rhythm.
• Identify conduction abnormalities.
• Assess atrial and ventricular electrical activity.
• Identify certain arrhythmias.
• Detect patterns suggestive of myocardial ischemia or infarction.
• Assess changes associated with electrolyte abnormalities.
• Evaluate patients with chest pain, palpitations, syncope or dizziness.
• Monitor selected patients receiving cardiac medications.
• Assist in evaluation of cardiac conditions.

The American Heart Association notes that ECG can help diagnose and monitor conditions such as arrhythmias, cardiomyopathy, coronary artery disease, heart attack and other cardiac disorders.

3. Principle of ECG

The heart generates electrical activity during each cardiac cycle.

The electrical impulse normally begins in the sinoatrial (SA) node, spreads through the atria, reaches the atrioventricular (AV) node, passes through the His-Purkinje conduction system and activates the ventricles.

Basic Electrical Pathway:

SA Node → Atrial Depolarization → AV Node → Bundle of His → Bundle Branches → Purkinje Fibers → Ventricular Depolarization

Depolarization

Depolarization represents electrical activation of cardiac muscle.

Repolarization

Repolarization represents recovery of the cardiac cells toward their resting electrical state.

4. ECG Paper and Calibration

Standard ECG paper is divided into small and large squares.

ECG Paper Measurement	Standard Value
1 small square horizontally	0.04 second
1 large square horizontally	0.20 second
5 large squares	1 second
10 mm vertically	1 mV

NORCET High-Yield:
Standard ECG paper speed = 25 mm/second
Standard calibration = 10 mm/mV

ECG Grid

At a paper speed of 25 mm/second:

• Small square = 0.04 sec
• 5 small squares = 1 large square = 0.20 sec
• 25 small squares = 1 second
• 300 large squares = 60 seconds

5. ECG Waves

Wave	Represents
P Wave	Atrial depolarization
QRS Complex	Ventricular depolarization
T Wave	Ventricular repolarization
U Wave	May be seen after T wave; its significance varies and it is not always visible

P Wave: The P wave represents atrial depolarization. A normal sinus P wave is generally upright in lead II.

QRS Complex: The QRS complex represents ventricular depolarization. It normally occurs after the P wave.

T Wave: The T wave represents ventricular repolarization.

6. ECG Intervals and Segments

Component	Meaning
PR Interval	Time from beginning of atrial depolarization to beginning of ventricular depolarization
QRS Duration	Duration of ventricular depolarization
ST Segment	Period between ventricular depolarization and repolarization
QT Interval	Duration of ventricular electrical activity from depolarization through repolarization

PR Interval

Normal PR interval is approximately 0.12–0.20 seconds.

QRS Duration

A normal QRS complex is generally less than 0.12 seconds.

ST Segment

The ST segment is normally close to the isoelectric line. ST elevation or depression may have important clinical significance depending on the clinical context and ECG pattern.

QT Interval

The QT interval varies with heart rate, so corrected QT (QTc) is commonly considered when assessing QT prolongation.

Important: Do not interpret an isolated ECG value without considering heart rate, clinical condition, medications, electrolytes and the complete ECG pattern.

7. Normal ECG Values

Parameter	Common Reference
Adult heart rate	60–100 beats/minute
PR interval	0.12–0.20 sec
QRS duration	<0.12 sec
Standard paper speed	25 mm/sec
Standard calibration	10 mm/mV

8. ECG Leads

A standard diagnostic 12-lead ECG provides different electrical views of the heart.

Very Important: A standard 12-lead ECG uses 10 electrodes to produce 12 leads/views.

12 Leads

• I
• II
• III
• aVR
• aVL
• aVF
• V1
• V2
• V3
• V4
• V5
• V6

9. Limb Leads

Bipolar Limb Leads

• Lead I
• Lead II
• Lead III

Augmented Limb Leads

• aVR
• aVL
• aVF

Lead	General View
I	Left lateral aspect
II	Inferior aspect
III	Inferior aspect
aVR	Right-sided electrical view
aVL	High lateral view
aVF	Inferior view

10. Chest Leads V1–V6

The precordial or chest leads provide horizontal-plane views of cardiac electrical activity.

Lead	General Region
V1	Septal / right anterior view
V2	Septal view
V3	Anterior transition region
V4	Anterior view
V5	Lateral view
V6	Lateral view

11. ECG Electrode Placement

V1: 4th intercostal space, right sternal border.

V2: 4th intercostal space, left sternal border.

V3: Midway between V2 and V4.

V4: 5th intercostal space at the midclavicular line.

V5: Same horizontal level as V4 at the anterior axillary line.

V6: Same horizontal level as V4 and V5 at the midaxillary line.

Common Exam Error: Do not place V1 and V2 too high. Incorrect precordial electrode placement can alter ECG morphology and potentially affect interpretation.

12. ECG Recording Procedure

Step 1: Identify the patient using appropriate identifiers.

Step 2: Explain the procedure to the patient.

Step 3: Provide privacy and position the patient comfortably, usually supine when clinically appropriate.

Step 4: Expose the required areas while maintaining dignity.

Step 5: Prepare the skin. Remove excessive oil/sweat and manage hair if it interferes with electrode contact according to policy.

Step 6: Apply the limb and chest electrodes in their correct anatomical positions.

Step 7: Connect the ECG leads correctly.

Step 8: Ask the patient to remain still and avoid talking during recording.

Step 9: Record the ECG with appropriate calibration and paper speed.

Step 10: Check the tracing for artifacts and verify that the recording is technically adequate.

Step 11: Remove electrodes and clean the patient as appropriate.

Step 12: Document and communicate clinically significant findings according to local policy.

13. Patient Preparation

• Explain that the test records electrical activity and does not send electricity into the patient.
• Encourage the patient to remain relaxed.
• Position appropriately.
• Maintain privacy.
• Keep the patient still during recording.
• Ensure good electrode-skin contact.
• Remove interfering clothing from electrode sites.
• Use appropriate skin preparation.

Patient Education: A routine ECG is generally painless. The electrodes detect electrical activity; the ECG machine does not deliver an electrical shock to the patient.

14. How to Calculate Heart Rate

Method 1 – 300 Rule

For a regular rhythm:

Heart Rate = 300 ÷ Number of large squares between two consecutive R waves

Example:

If there are 4 large squares between R waves:

300 ÷ 4 = 75 beats/minute

Method 2 – 1500 Rule

Heart Rate = 1500 ÷ Number of small squares between two R waves

Method 3 – 6-Second Method

For irregular rhythms, count the number of QRS complexes in a 6-second strip and multiply by 10.

Example:
7 QRS complexes in 6 seconds

7 × 10 = 70 beats/minute

15. How to Assess Cardiac Rhythm

Assess:

• R-R regularity.
• P-P regularity.
• Presence of P waves.
• Relationship between P waves and QRS complexes.
• PR interval.
• QRS duration.
• Overall rhythm pattern.

Regular Rhythm

The R-R intervals are approximately equal.

Irregular Rhythm

The R-R intervals vary.

16. Cardiac Axis

The electrical axis describes the general direction of ventricular depolarization in the frontal plane.

For basic nursing-level ECG interpretation, leads I and aVF can provide a simple approach to determining the general QRS axis.

Lead I	aVF	General Interpretation
Positive	Positive	Usually normal axis
Positive	Negative	May indicate leftward axis; assess lead II to refine
Negative	Positive	May indicate right axis deviation
Negative	Negative	Extreme axis pattern

Axis interpretation should be performed using the complete ECG and appropriate clinical context rather than relying on one lead alone.

17. Systematic ECG Interpretation

A systematic approach reduces the chance of missing important findings.

1. Patient Information
Check patient name/identifier, date, time and clinical indication.

2. Rate
Determine ventricular rate.

3. Rhythm
Assess regularity and P-QRS relationship.

4. P Waves
Check presence, morphology and relationship to QRS.

5. PR Interval
Assess PR interval and its consistency.

6. QRS
Assess width and morphology.

7. Axis
Assess frontal-plane QRS axis when appropriate.

8. ST Segment
Look for significant elevation or depression in the appropriate leads.

9. T Waves
Assess T-wave direction, size and morphology.

10. QT/QTc
Assess QT interval in relation to heart rate.

11. Compare Previous ECG
When available, comparison with prior ECGs can be clinically valuable.

Easy Sequence:

Rate → Rhythm → P → PR → QRS → Axis → ST → T → QT → Compare

18. Normal Sinus Rhythm

Typical features include:

• Rate approximately 60–100 beats/minute in adults.
• Regular rhythm.
• Normal P wave before each QRS.
• Consistent PR interval.
• Narrow QRS in the absence of a conduction abnormality.
• Normal overall morphology.

19. Sinus Bradycardia

Sinus bradycardia is a sinus rhythm with a rate below the usual adult resting range of 60 beats/minute.

Possible Causes

• Sleep.
• Athletic conditioning.
• Increased vagal tone.
• Hypothermia.
• Some medications.
• Inferior myocardial infarction.
• Conduction system disease.

The clinical significance depends on symptoms, hemodynamic status and the underlying cause.

20. Sinus Tachycardia

Sinus tachycardia is a sinus rhythm with an adult rate above 100 beats/minute.

Possible Causes

• Fever.
• Pain.
• Anxiety.
• Exercise.
• Dehydration.
• Hypovolemia.
• Hypoxia.
• Anemia.
• Some medications or stimulants.

Clinical Principle: Sinus tachycardia is often a response to an underlying condition. The cause should be assessed rather than focusing only on the heart rate.

21. Atrial Fibrillation

Atrial fibrillation is characterized by disorganized atrial electrical activity and an irregularly irregular ventricular response in typical cases.

Common ECG Features

• Irregularly irregular R-R intervals.
• No consistent normal P waves.
• Variable baseline activity may be present.
• QRS may remain narrow when ventricular conduction is normal.

Atrial fibrillation can increase the risk of thromboembolic complications. Management requires clinical assessment and appropriate risk-based treatment.

22. Atrial Flutter

Atrial flutter is an atrial tachyarrhythmia commonly associated with organized rapid atrial activity.

ECG Features

• Characteristic repetitive flutter waves.
• Often described as a "saw-tooth" pattern, particularly in inferior leads.
• Ventricular response may be regular or variable depending on conduction.

23. Premature Ventricular Complex

A PVC is an early ventricular depolarization that arises from ventricular tissue rather than the normal conduction pathway.

Typical ECG Features

• Premature beat.
• Usually wide and abnormal QRS morphology.
• Usually no preceding normal P wave directly associated with the PVC.
• May be followed by a compensatory pause.

24. Ventricular Tachycardia

Ventricular tachycardia is a rapid rhythm originating from the ventricles.

Common ECG Features

• Rapid ventricular rate.
• Usually wide QRS complexes.
• Possible AV dissociation.
• Capture or fusion beats may occur.

Emergency: Sustained ventricular tachycardia can cause hemodynamic instability and may deteriorate into ventricular fibrillation. Immediate clinical assessment and appropriate emergency management are required.

25. Ventricular Fibrillation

Ventricular fibrillation is a chaotic ventricular rhythm in which effective coordinated ventricular contraction is absent.

ECG Appearance

• Chaotic electrical activity.
• No identifiable organized P-QRS-T sequence.
• No effective cardiac output.

VF is a cardiac arrest rhythm. Immediate resuscitation according to current BLS/ALS protocols is required.

26. AV Blocks

First-Degree AV Block

• PR interval is prolonged.
• Every P wave is followed by a QRS complex.
• PR interval is typically >0.20 seconds.

Second-Degree AV Block – Mobitz I

• Progressive PR prolongation.
• Then a QRS complex is dropped.
• Pattern repeats.

Second-Degree AV Block – Mobitz II

• PR intervals are usually constant.
• Unexpected dropped QRS complexes occur.
• Can progress to complete heart block.

Third-Degree AV Block

• Complete AV dissociation.
• Atrial and ventricular activity occur independently.
• Requires urgent clinical evaluation.

Memory Tip:
Mobitz I → Longer, Longer, Drop
Mobitz II → Constant, Drop

27. ECG Changes in Myocardial Infarction

ECG findings in acute myocardial infarction depend on the location, timing and extent of ischemia/injury.

Possible Ischemic Changes

• ST-segment depression.
• ST-segment elevation in appropriate leads.
• T-wave inversion.
• Pathological Q waves may develop with myocardial necrosis/infarction.

ECG findings must always be interpreted together with symptoms, serial ECGs when indicated, cardiac biomarkers and other clinical information.

28. MI Lead Localization

Myocardial Region	Common ECG Leads
Inferior	II, III, aVF
Septal	V1, V2
Anterior	V3, V4
Anterolateral	V3–V6, I, aVL depending on extent
Lateral	I, aVL, V5, V6

NORCET Memory:

Inferior → II, III, aVF
Septal → V1, V2
Anterior → V3, V4
Lateral → I, aVL, V5, V6

29. STEMI and ST Elevation

ST-segment elevation in appropriate contiguous leads, together with the clinical presentation and other findings, may indicate acute coronary occlusion and STEMI.

Current ACS pathways emphasize rapid ECG assessment in patients with suspected acute coronary syndrome. AHA quality measures identify obtaining a 12-lead ECG within 10 minutes of arrival for acute chest pain or suspected ACS as an important performance measure. 1

Important: ST elevation is not synonymous with myocardial infarction in every situation. Other conditions can produce ST-segment elevation. Clinical context and expert interpretation are essential.

30. ECG Artifacts

Artifacts are unwanted signals that interfere with ECG interpretation.

Artifact	Possible Cause
Baseline wander	Respiration, movement, poor electrode contact
Muscle artifact	Patient shivering or muscle tension
Electrical interference	Nearby electrical equipment or poor grounding
Loose electrode artifact	Poor electrode-skin contact
Patient movement	Talking, coughing, moving limbs or changing position

How to Reduce Artifacts

• Ask the patient to remain still.
• Keep the patient warm if shivering.
• Prepare the skin properly.
• Check electrode adhesion.
• Replace dried or defective electrodes.
• Check cable connections.
• Move unnecessary electrical equipment away when appropriate.

31. Nursing Responsibilities During ECG

Before ECG

• Verify patient identity.
• Explain procedure.
• Assess clinical indication.
• Provide privacy.
• Position the patient appropriately.
• Prepare skin.
• Check ECG machine.

During ECG

• Place electrodes correctly.
• Ensure proper cable connection.
• Ask patient to remain relaxed.
• Observe the patient for symptoms.
• Monitor for chest pain, dyspnea, dizziness or deterioration.
• Check tracing quality.

After ECG

• Remove electrodes.
• Provide comfort.
• Label the ECG correctly.
• Document the procedure.
• Report clinically significant abnormalities according to local protocol.
• Compare with previous ECG when available and appropriate.

32. ECG in Emergency Situations

ECG is especially important in patients presenting with symptoms such as:

• Chest pain or pressure.
• Shortness of breath.
• Palpitations.
• Syncope.
• Unexplained dizziness.
• Suspected myocardial ischemia.
• Suspected arrhythmia.
• Cardiac arrest.

Chest Pain + ECG Changes = Urgent Clinical Assessment

Never delay emergency evaluation because a patient appears comfortable or because one ECG appears normal when clinical suspicion remains significant.

33. Documentation

Document:

• Date and time.
• Indication for ECG.
• Patient symptoms.
• Patient position if clinically relevant.
• 12-lead ECG performed.
• Machine settings/calibration when relevant.
• Any technical difficulties.
• Artifacts or electrode-placement issues.
• Important findings communicated to the responsible clinician.
• Actions taken after abnormal findings.

34. Common ECG Recording Errors

• Incorrect patient identification.
• Incorrect electrode placement.
• V1/V2 placement too high.
• Loose electrodes.
• Dry electrodes.
• Patient talking during recording.
• Patient shivering.
• Incorrect limb lead connections.
• Failure to check calibration.
• Failure to check ECG quality.
• Failure to document significant clinical symptoms.

Golden Rule: Correct electrode placement + good skin contact + patient stillness = Better quality ECG.

35. Important NORCET Exam Points

• ECG records electrical activity of the heart.
• 12-lead ECG uses 10 electrodes.
• Standard ECG paper speed = 25 mm/sec.
• Standard calibration = 10 mm/mV.
• 1 small square = 0.04 sec.
• 1 large square = 0.20 sec.
• P wave = atrial depolarization.
• QRS = ventricular depolarization.
• T wave = ventricular repolarization.
• Normal PR interval = approximately 0.12–0.20 sec.
• Normal QRS duration = generally <0.12 sec.
• V1 = 4th intercostal space, right sternal border.
• V2 = 4th intercostal space, left sternal border.
• V3 = midway between V2 and V4.
• V4 = 5th intercostal space, midclavicular line.
• V5 = anterior axillary line.
• V6 = midaxillary line.
• II, III, aVF = inferior region.
• I, aVL, V5, V6 = lateral region.
• V1–V2 = septal region.
• V3–V4 = anterior region.
• 300 rule is useful for regular rhythms.
• 6-second method is useful for irregular rhythms.
• Atrial fibrillation = irregularly irregular rhythm with absent consistent P waves.
• Ventricular fibrillation = chaotic ventricular rhythm associated with cardiac arrest.

36. Frequently Asked Questions

Q1. What does ECG stand for?

ECG stands for Electrocardiogram.

Q2. What does an ECG measure?

It records the electrical activity of the heart.

Q3. How many electrodes are used for a standard 12-lead ECG?

A standard 12-lead ECG uses 10 electrodes.

Q4. What does the P wave represent?

The P wave represents atrial depolarization.

Q5. What does the QRS complex represent?

The QRS complex represents ventricular depolarization.

Q6. What does the T wave represent?

The T wave represents ventricular repolarization.

Q7. What is the normal PR interval?

Approximately 0.12–0.20 seconds.

Q8. What is the standard ECG paper speed?

The standard paper speed is 25 mm/second.

Q9. Where is V1 placed?

V1 is placed at the 4th intercostal space at the right sternal border.

Q10. Where is V4 placed?

V4 is placed at the 5th intercostal space at the midclavicular line.

Q11. Which leads represent the inferior wall?

Leads II, III and aVF.

Q12. Which rhythm is classically irregularly irregular?

Atrial fibrillation.

Q13. What is the 300 rule?

For a regular rhythm, heart rate can be estimated by dividing 300 by the number of large squares between consecutive R waves.

Q14. What is the 6-second method?

Count QRS complexes in a 6-second strip and multiply by 10 to estimate the heart rate.

Q15. Why is correct electrode placement important?

Incorrect electrode placement can change ECG morphology and may lead to incorrect interpretation.

37. ECG MCQs Practice – NORCET

Q1. ECG stands for:
A. Electrocardiogram
B. Electroencephalogram
C. Echocardiography
D. Electromyogram

Q2. A standard 12-lead ECG uses how many electrodes?
A. 6
B. 8
C. 10
D. 12

Q3. The P wave represents:
A. Ventricular repolarization
B. Atrial depolarization
C. Ventricular depolarization
D. AV block

Q4. The QRS complex represents:
A. Atrial repolarization
B. Atrial depolarization
C. Ventricular depolarization
D. Ventricular relaxation only

Q5. The T wave represents:
A. Atrial depolarization
B. Ventricular repolarization
C. Ventricular depolarization
D. SA node discharge

Q6. Standard ECG paper speed is:
A. 10 mm/sec
B. 15 mm/sec
C. 25 mm/sec
D. 50 cm/sec

Q7. One small ECG square horizontally represents:
A. 0.01 sec
B. 0.04 sec
C. 0.10 sec
D. 0.20 sec

Q8. One large ECG square represents:
A. 0.04 sec
B. 0.10 sec
C. 0.20 sec
D. 1 second

Q9. Normal PR interval is approximately:
A. 0.02–0.04 sec
B. 0.12–0.20 sec
C. 0.30–0.40 sec
D. 0.50–0.60 sec

Q10. V1 is placed at:
A. 5th intercostal space, left midclavicular line
B. 4th intercostal space, right sternal border
C. 4th intercostal space, left midaxillary line
D. 6th intercostal space, right sternal border

Q11. V4 is placed at:
A. 2nd intercostal space
B. 4th intercostal space
C. 5th intercostal space at midclavicular line
D. 6th intercostal space at midaxillary line

Q12. Which leads commonly represent the inferior wall?
A. I and aVL
B. V1 and V2
C. II, III and aVF
D. V5 and V6 only

Q13. Which leads are commonly associated with the lateral wall?
A. I, aVL, V5 and V6
B. V1 and V2
C. II and III only
D. aVR only

Q14. A rhythm that is classically irregularly irregular is:
A. Sinus rhythm
B. Atrial fibrillation
C. Complete heart block
D. Ventricular fibrillation

Q15. Which rhythm is characterized by chaotic ventricular electrical activity?
A. Sinus bradycardia
B. Atrial flutter
C. Ventricular fibrillation
D. First-degree AV block

Q16. In first-degree AV block, the PR interval is:
A. Shortened
B. Prolonged
C. Always absent
D. Always variable

Q17. The "300 rule" is used to estimate:
A. Blood pressure
B. Oxygen saturation
C. Heart rate
D. Cardiac output

Q18. Seven QRS complexes are present in a 6-second ECG strip. Approximate heart rate is:
A. 40/min
B. 50/min
C. 70/min
D. 100/min

Q19. Which ECG component represents ventricular repolarization?
A. P wave
B. QRS complex
C. T wave
D. PR interval

Q20. Which is an important way to reduce ECG artifact?
A. Ask the patient to talk continuously
B. Ask the patient to remain still
C. Remove all electrodes
D. Place electrodes randomly

Q21. The V3 electrode is placed:
A. Between V1 and V2
B. Between V2 and V4
C. Between V4 and V5
D. At the right sternal border

Q22. V6 is placed at the:
A. Midaxillary line
B. Midclavicular line
C. Right sternal border
D. Suprasternal notch

Q23. Which rhythm is associated with progressive PR prolongation followed by a dropped QRS?
A. Mobitz I
B. Mobitz II
C. Complete heart block
D. Atrial fibrillation

Q24. Which finding may indicate ventricular tachycardia?
A. Rapid wide-complex rhythm
B. Normal sinus P waves before every QRS
C. Slow regular rhythm only
D. Isolated normal P wave

Q25. In a patient with suspected acute coronary syndrome, a 12-lead ECG is important because it can:
A. Measure blood glucose
B. Record cardiac electrical activity and identify important ischemic patterns
C. Measure hemoglobin
D. Measure body temperature

38. Answer Key with Explanations

Q	Answer	Explanation
1	A	ECG means electrocardiogram.
2	C	A standard 12-lead ECG uses 10 electrodes.
3	B	P wave represents atrial depolarization.
4	C	QRS represents ventricular depolarization.
5	B	T wave represents ventricular repolarization.
6	C	Standard ECG paper speed is 25 mm/sec.
7	B	One small square represents 0.04 second.
8	C	One large square contains five small squares and represents 0.20 second.
9	B	Normal PR interval is approximately 0.12–0.20 sec.
10	B	V1 is placed at the 4th intercostal space at the right sternal border.
11	C	V4 is placed at the 5th intercostal space at the midclavicular line.
12	C	II, III and aVF view the inferior region.
13	A	I, aVL, V5 and V6 commonly represent lateral regions.
14	B	Atrial fibrillation commonly produces an irregularly irregular ventricular rhythm.
15	C	Ventricular fibrillation produces chaotic ventricular electrical activity.
16	B	First-degree AV block is characterized by a prolonged PR interval.
17	C	The 300 rule estimates heart rate in a regular rhythm.
18	C	7 × 10 = 70 beats/minute.
19	C	T wave represents ventricular repolarization.
20	B	Patient movement can produce artifact, so stillness improves tracing quality.
21	B	V3 is positioned midway between V2 and V4.
22	A	V6 is placed at the midaxillary line at the same horizontal level as V4/V5.
23	A	Mobitz I demonstrates progressive PR prolongation followed by a dropped QRS.
24	A	Ventricular tachycardia commonly appears as a rapid wide-complex rhythm.
25	B	ECG records cardiac electrical activity and can demonstrate important ischemic patterns.

39. Quick Revision – ECG One Shot

ECG BASICS

• ECG = Electrical activity of heart
• 12-lead ECG = 10 electrodes
• Paper speed = 25 mm/sec
• Calibration = 10 mm/mV
• Small square = 0.04 sec
• Large square = 0.20 sec

WAVES

• P = Atrial depolarization
• QRS = Ventricular depolarization
• T = Ventricular repolarization

NORMAL VALUES

• Adult HR = 60–100/min
• PR = 0.12–0.20 sec
• QRS = <0.12 sec

CHEST LEADS

• V1 → 4th ICS, right sternal border
• V2 → 4th ICS, left sternal border
• V3 → Between V2 and V4
• V4 → 5th ICS, midclavicular line
• V5 → Anterior axillary line
• V6 → Midaxillary line

MI LOCALIZATION

• Inferior → II, III, aVF
• Septal → V1, V2
• Anterior → V3, V4
• Lateral → I, aVL, V5, V6

HEART RATE

Regular rhythm: 300 ÷ large squares

Irregular rhythm: QRS in 6 seconds × 10

RHYTHM MEMORY

• AF → Irregularly irregular
• Mobitz I → Longer, Longer, Drop
• Mobitz II → Constant, Drop
• VF → Chaotic ventricular rhythm

40. Clinical Updates

• The American Heart Association's current patient-facing ECG information describes ECG as a test that records the electrical activity of the heart and can help identify several cardiac conditions. 2
• The 2025 ACC/AHA/ACEP/NAEMSP/SCAI guideline provides updated recommendations for management of acute coronary syndromes and emphasizes timely evaluation of suspected ACS. 3
• AHA quality-improvement measures identify obtaining a 12-lead ECG within 10 minutes of arrival for patients with acute chest pain or suspected ACS as an important emergency-care performance measure. 4
• The ESC's 2025 acute cardiovascular-care toolkit continues to use immediate 12-lead ECG as part of the initial assessment of appropriate patients with suspected acute cardiovascular conditions. 5

Clinical Safety Note: ECG interpretation requires appropriate clinical training. An ECG should not be interpreted in isolation. Patient symptoms, vital signs, previous ECGs, medications, laboratory findings and the complete clinical situation must be considered.

41. Conclusion

ECG is one of the most important cardiovascular investigations that every nursing student should understand. For examination preparation, focus first on ECG waves, intervals, normal values, lead placement, heart-rate calculation and systematic interpretation.

For clinical practice, nurses should additionally understand patient preparation, correct electrode placement, artifact prevention, recognition of abnormal rhythms, emergency escalation and accurate documentation.

Student Revision Formula:

Learn the Waves → Learn the Leads → Learn Normal Values → Practice Rate Calculation → Identify Rhythms → Practice Clinical MCQs

Reading ECG repeatedly becomes much easier when you follow the same systematic sequence every time.

📚 Continue Your Nursing Exam Preparation

Preparing for NORCET, AIIMS Nursing, BSc Nursing, GNM or Staff Nurse Exams?

Read → Revise → Practice MCQs → Check Answers → Evaluate Your Knowledge

Keep learning, keep practicing and keep improving your clinical knowledge. ❤️

Educational Disclaimer:

This article is intended for nursing education, examination preparation and general learning. It is not a substitute for clinical training, institutional protocols, professional ECG interpretation or medical advice. ECG interpretation and emergency cardiac management should be performed by appropriately trained healthcare professionals according to current guidelines, patient condition and institutional protocols.

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