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Questions and Answers
Which lead is used in determining the ECG axis when looking for equiphasic leads?
Which lead is used in determining the ECG axis when looking for equiphasic leads?
The QT interval represents the time from the beginning of the T wave to the end of the QRS complex.
The QT interval represents the time from the beginning of the T wave to the end of the QRS complex.
False
What is the maximum normal duration of the QT interval for males?
What is the maximum normal duration of the QT interval for males?
0.42 seconds
The maximum duration for a prolonged QT interval is greater than ______ seconds.
The maximum duration for a prolonged QT interval is greater than ______ seconds.
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Match the following QT interval duration limits with the respective gender:
Match the following QT interval duration limits with the respective gender:
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What is one characteristic to examine in an ECG for rhythm analysis?
What is one characteristic to examine in an ECG for rhythm analysis?
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The P wave represents an impulse from the sinoatrial node (SAN).
The P wave represents an impulse from the sinoatrial node (SAN).
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What degree of AV node block is classified as the most serious?
What degree of AV node block is classified as the most serious?
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Lead II in bipolar leads is placed between the right arm (RA) and the ______.
Lead II in bipolar leads is placed between the right arm (RA) and the ______.
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Match the following leads to their definitions:
Match the following leads to their definitions:
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What is the minimum value for discordant ST elevation to be considered significant in the diagnosis of myocardial infarction (MI)?
What is the minimum value for discordant ST elevation to be considered significant in the diagnosis of myocardial infarction (MI)?
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A left bundle branch block (LBBB) pattern guarantees the presence of myocardial infarction.
A left bundle branch block (LBBB) pattern guarantees the presence of myocardial infarction.
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What leads show concordant ST elevation greater than 1 mm for diagnosing MI?
What leads show concordant ST elevation greater than 1 mm for diagnosing MI?
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A threshold of discordant ST segment elevation greater than ___ mm is significant for diagnosing MI.
A threshold of discordant ST segment elevation greater than ___ mm is significant for diagnosing MI.
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Match the following terms with their descriptions:
Match the following terms with their descriptions:
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What does an R/S ratio greater than 1 in lead V1 indicate?
What does an R/S ratio greater than 1 in lead V1 indicate?
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P-pulmonale is most commonly caused by asthma.
P-pulmonale is most commonly caused by asthma.
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What is one of the characteristics of Left Bundle Branch Block (LBBB) in ECG analysis?
What is one of the characteristics of Left Bundle Branch Block (LBBB) in ECG analysis?
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The Sokolow Lyon index indicates left ventricular hypertrophy if the combined total of the V5 or V6 R wave and VI or V4 S wave is greater than ______ mm.
The Sokolow Lyon index indicates left ventricular hypertrophy if the combined total of the V5 or V6 R wave and VI or V4 S wave is greater than ______ mm.
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Match the following ECG features with their meanings:
Match the following ECG features with their meanings:
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What is the direction of Vector 1 in the ECG?
What is the direction of Vector 1 in the ECG?
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Vector 2 causes positive deflection in lead V1.
Vector 2 causes positive deflection in lead V1.
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What is the heart rate range for accelerated idioventricular rhythm?
What is the heart rate range for accelerated idioventricular rhythm?
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The last part to be depolarized in the heart is the ___________ portion.
The last part to be depolarized in the heart is the ___________ portion.
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Match the vector with its description:
Match the vector with its description:
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What indicates right ventricular hypertrophy (RVH) when associated with RBBB?
What indicates right ventricular hypertrophy (RVH) when associated with RBBB?
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Left bundle branch block (LBBB) can be classified as a bifascicular block by itself.
Left bundle branch block (LBBB) can be classified as a bifascicular block by itself.
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What is the primary ECG finding of a concordant ST elevation in the presence of left bundle branch block?
What is the primary ECG finding of a concordant ST elevation in the presence of left bundle branch block?
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The Sgarbossa Criteria is used to diagnose __________ along with LBBB.
The Sgarbossa Criteria is used to diagnose __________ along with LBBB.
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Match the following types of blocks with their description:
Match the following types of blocks with their description:
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What is the maximum normal duration of a narrow QRS complex?
What is the maximum normal duration of a narrow QRS complex?
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A very wide QRS complex is defined as being greater than 0.12 seconds.
A very wide QRS complex is defined as being greater than 0.12 seconds.
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What is the normal duration of one small box on an ECG?
What is the normal duration of one small box on an ECG?
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The maximum deflection in ECG is observed in the ______ complex.
The maximum deflection in ECG is observed in the ______ complex.
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Match the following QRS complex durations with their classifications:
Match the following QRS complex durations with their classifications:
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What is indicated by a bifid P wave in an ECG?
What is indicated by a bifid P wave in an ECG?
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Tall and peaked P waves can indicate right atrial enlargement associated with COPD.
Tall and peaked P waves can indicate right atrial enlargement associated with COPD.
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What is the equation to calculate the corrected QT interval?
What is the equation to calculate the corrected QT interval?
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In left ventricular hypertrophy, the heart's _____ mass on the left increases.
In left ventricular hypertrophy, the heart's _____ mass on the left increases.
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Match the following types of enlargement with their ECG characteristics:
Match the following types of enlargement with their ECG characteristics:
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What is the final destination of the depolarization pathway in the heart?
What is the final destination of the depolarization pathway in the heart?
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The QRS complex is the sum of the vectors representing septal, free wall, and posterobasal LV depolarization.
The QRS complex is the sum of the vectors representing septal, free wall, and posterobasal LV depolarization.
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What device is primarily used to measure the electrical signals of the heart?
What device is primarily used to measure the electrical signals of the heart?
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The __________ flow from the right to left in relation to the right and left electrodes.
The __________ flow from the right to left in relation to the right and left electrodes.
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Match the following phases of ventricular depolarization with their corresponding vectors:
Match the following phases of ventricular depolarization with their corresponding vectors:
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What is the normal heart rate range for sinus rhythm?
What is the normal heart rate range for sinus rhythm?
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A prolonged PR interval indicates a defect or block in the conduction pathway.
A prolonged PR interval indicates a defect or block in the conduction pathway.
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What does the P wave in an ECG represent?
What does the P wave in an ECG represent?
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The time taken from the start of atrial depolarization to the start of ventricular depolarization is known as the ______.
The time taken from the start of atrial depolarization to the start of ventricular depolarization is known as the ______.
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Match the types of bundle branch block with their description:
Match the types of bundle branch block with their description:
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What is the normal duration of a PR interval?
What is the normal duration of a PR interval?
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Every QRS complex in a normal ECG is preceded by a P wave.
Every QRS complex in a normal ECG is preceded by a P wave.
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What morphology does a normal P wave have?
What morphology does a normal P wave have?
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Study Notes
ECG Axis Determination
- Method: Use leads I, II, III, aVL, and aVF to count the height of the QRS complex
- Equiphasic Leads: Leads where the R wave height equals the S wave height
- Axis Location: Identify the lead showing the biggest QRS complex deflection
- Perpendicular Axis: The axis perpendicular to identified lead will show significant deflections in the leads
QT Interval
- Definition: Represents time for ventricle to recover and prepare for the next heart beat
- Measurement: Time between start of QRS complex and end of T wave
- Features: Includes QRS, ST segment and T wave
-
Normal Duration:
- Females: ≤ 0.44 seconds
- Males: ≤ 0.42 seconds
- Prolonged: > 0.48 seconds
ECG Axis Diagram
- Contains different axes angles and leads, including normal, northwest, rightward and leftward axis
ECG Approach
- QRS Complex Width: Narrow/normal or wide
- Rhythm: Examine for different rhythm types: Idioventricular, accelerated idioventricular, ventricular arrhythmias, Bundle Branch Block (BBB), Atrial rhythm, Junctional rhythm, etc.
- PR Intervals: Normal, short, prolonged
- P Wave: Normal, Abnormal, Absent
- Presence of Other Waves: P, QRS, T
- AV Block: Degree (1st, 2nd, or 3rd-degree)
- Ventricular Tachycardia: Wider QRS complexes
Leads
-
Bipolar Leads:
- Lead I: Between Right Arm (RA) and Left Arm (LA)
- Lead II: Between Right Arm (RA) and Left Leg (LL)
- Lead III: Between Left Arm (LA) and Left Leg (LL)
-
Augmented Unipolar Leads:
- AVR: Perpendicular to Lead III
- AVL: Perpendicular to Lead II
- AVF: Perpendicular to Lead I
Criteria for Myocardial Infarction (MI)
- V5, V6: Concordant ST elevation > 1 mm, Discordant ST elevation > 5 mm, Concordant ST depression > 1 mm
- VI, V4: Abnormally discordant ST segment ≥ 5 mm, Discordant ST segment ≥ 1 mm, Concordant ST segment ≥ 1 mm
ECG Tracings
- LBBB No MI: Shows Left Bundle Branch Block (LBBB) but no MI
- LBBB + Acute MI: Shows LBBB and acute MI
Acute MI With LBBB
- Concordant Elevation > 1 mm: Acute MI with LBBB and a consistent ST segment elevation over 1 mm
- Discordant Elevation > 5 mm: ST segment elevation deviated in direction opposite to QRS deflection
ECG Findings
-
Sokolow Lyon Index:
- V5 or V6 R wave + VI or V4 S wave → >35mm LVH
- aVL > 11mm → LVH
- 2° ST/T changes (positive) due to strain/pressure overload (e.g., aortic stenosis/chronic HTN)
- Left bundle branch block (LBBB)
-
Right Ventricular Hypertrophy (RVH):
- Axis: Between leads III (120°) and aVF (90°)
- Rightward axis
- Causes:
- RVH
- VI: R/S ratio > 1
- 2° ST changes
- Mitral stenosis (ms) + RVH
-
P-pulmonale:
- In leads II, III, aVF
- Most common cause: COPD
- Hyperinflated lung
- Downward diaphragm push
- Axis shifts to 90°
-
COPD Signs:
- Prominent complexes in aVF and lead II
- Absent complexes in lead I → Lead I sign
- QRS complex: Narrow
- VI to V6: Poor R-wave progression
- P pulmonale
- Lead I sign (+)
Vectors
-
Vector 1:
- Interventricular (IV) septum
- Left Bundle Branch (LBB) shorter than Right Bundle Branch (RBB): Left side of IV septum activated first
- Direction: Right side, anteriorly and inferiorly
- Right sided leads: Positive deflection
- Left sided leads: Negative deflection
- Most predominant, right lead
-
Vector 2:
- Free wall depolarization
- Direction: Right to Left + Endocardium → Epicardium
- Left posteriorly and superiorly
- Right sided: Negative deflection in lead V1
- Left sided: Positive deflection in leads V5 and V6 (Big R)
-
Vector 3:
- Last part (Posterobasal portion) to be depolarized
- Direction: Superiorly and Posteriorly
- No deflection
Wide QRS: Causes
-
Ventricular activation via alternate pathway:
-
0.16 s
-
Myocardial cell-to-cell conduction
-
Ventricular generated rhythm:
- Idioventricular: 15-40 bpm
- Accelerated idioventricular: 40-100 bpm
- Ventricular tachycardia: >100 bpm
-
RIGHT BBB (RBBB)
-
RVH with RBBB:
- Axis: B/W lead 1 & aVL → Leftward axis
- R/S ratio > 1: RVH
- RVH + Leftward axis: Biventricular hypertrophy
Blocks
- RBBB only: Unifascicular block
- RBBB + Lt anterior/posterior fascicular block (LAFB/LPFB): Bifascicular block
- LBBB: Bifascicular block (By itself)
- Bifascicular block + ↑ PR interval/mobitz block: Trifascicular block
LEFT BBB (LBBB)
- Axis: B/W lead I & AVL → Leftward axis
- V5, V6, AVL: LBBB morphology
Sgarbossa Criteria
- Used to diagnose MI along with LBBB
ECG Findings
-
VI or va:
- Concordant change: ST depression
- Discordant change: ST elevation
-
V5 or V6:
- Concordant ST elevation
Chronology of Reading ECG
- Start from lead II/rhythm strip:
-
QRS Complex:
- Big R:
- Small Q:
- Small R: (leads to Deep S)
- Regularity of QRS:
- P Wave:
- Rate:
- Axis:
- QT Interval:
QRS Complex
- Features: Maximum deflection. Synchronous ventricular depolarization
-
Duration:
- Normal/narrow QRS: 2-2.5 small boxes (100ms/0.1s)
- Wide QRS: > 0.12 s
- Very wide QRS: > 0.16 s
- 1 small box = 40 ms
Patient Parameters
- Time: 00:40:48
- Rhythm: Regular
- Rate: 150/min (1500/no.of small boxes/2 QRS complexes)
- Heart Rate: 60-100 bpm (Sinus) / 40-60 bpm (Atrial/Junctional) / 15-40 bpm (Ventricular)
Normal Pathway With Block
- 0.12 - 0.165
- Right Bundle Branch Block (RBBB) / Left Bundle Branch Block (LBBB)
Regularity of QRS Complexes
- Regular, fixed intervals
P Wave Analysis
-
Appearance: First wave. Produced by atrial depolarization from the SA node
- Right atrial depolarization: Ascending limb
- Left atrial depolarization: Descending limb
- Shape: Smooth and rounded
- Height and Width: Equal to 2.5mm
- Leads II, III or aVF: Upright (Normal), (may be inverted=P-pulmonale)
- Lead V₁: Inverted/Biphasic
- Normal: Every QRS is preceded by a P wave
PR Segment
- Definition: Impulse from P wave start to QRS complex start
- Parts:
- Atria
- AV node
- Intra-AV nodal (Normal AV nodal delay)
- Upper Part of Bundle of His
- Electrophysiology: Electrically inert; No deflection
PR Interval Analysis
- Duration: 0.12 -0.2 seconds (3-5 small boxes)
- Prolonged PR intervals (> 0.25): Defect/block (on regular pathway)
- Shortened PR intervals: Aberrant pathway between atria and ventricle (Bundle of Kent)
Atrial & Ventricular Enlargement
Atrial Enlargement
-
Right atrial enlargement:
- Abnormal P waves: Pathology of atrial origin
- Pointed P (P-pulmonale): Right atrial enlargement
- Tall & peaked: COPD
- Rate > 100 bpm: Atrial tachycardia
-
Left atrial enlargement:
- Bifid P wave: P mitrale
Ventricular Hypertrophy
-
Left ventricular hypertrophy (LVH):
- Axis: aVL(30°) - lead I (0°) → Leftward axis
- Causes:
- LVH (Left ventricular hypertrophy)
- ↑ muscle mass on left
- ↓ vector pushed to left
- Left side: ↑+ve deflection
- Right side: |-ve deflection
- LVH (Left ventricular hypertrophy)
- Note: Corrected QT interval: QT=QTRRQT = \frac{QT}{\sqrt{RR}}QT=RRQT
Route of Depolarization
- Sinus Node → Atria → AV Node → Bundle of His
- Bundle of His → Right Bundle Branch → Right Ventricle
- Bundle of His → Left Bundle Branch → Left Anterior Fascicle → Left Ventricle
- Bundle of His → Left Bundle Branch → Left Posterior Fascicle → Left Ventricle
- Purkinje Fibres → Right Ventricle
- Purkinje Fibres → Left Ventricle
Depolarization Vectors
- Septal depolarization: Vector 1
- Free wall depolarization: Vector 2
- Posterobasal LV depolarization: Vector 3
- QRS complex is the sum of these three vectors (Vector 1 + Vector 2 + Vector 3)
Flow of Current
- Downward deflection: Current flows away from the positive electrode
- Upward deflection: Current flows towards the positive electrode
ECG Instrumentation Diagram
- Galvanometer: Measures electrical signals of the heart
- Electrodes: Placed on right and left arm
- Lead: Connects the galvanometer
- Potential Difference: Measured between right and left electrodes
- ECG Recording: Electrical signal recorded as ECG
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Description
This quiz focuses on understanding the ECG axis determination and the QT interval. It covers key concepts such as equiphasic leads, axis location, and the normal duration of the QT interval for different genders. Test your knowledge on these important aspects of electrocardiography.
