The main purpose of the electrocardiogram is to:
A) Measure lung volumes during exercise
B) Record the heart’s electrical activity at the body surface
C) Estimate cardiac output by thermodilution
D) Visualize coronary arteries directly
Correct answer: B
Explanation: Surface electrodes detect voltage changes that reflect cardiac depolarization and repolarization.

 

The P wave on a standard electrocardiogram represents:
A) Ventricular depolarization
B) Atrial depolarization
C) Ventricular repolarization
D) Atrial repolarization
Correct answer: B
Explanation: The P wave is produced by atrial depolarization before atrioventricular conduction.

 

A normal P–R interval (from the beginning of P to the beginning of QRS) is approximately:
A) 60 to 100 milliseconds
B) 120 to 200 milliseconds
C) 220 to 300 milliseconds
D) 320 to 400 milliseconds
Correct answer: B
Explanation: Normal atrioventricular nodal conduction yields a P–R interval about 0.12–0.20 seconds.

 

A normal QRS complex duration is:
A) Less than 80 milliseconds
B) Less than 120 milliseconds
C) 140 to 160 milliseconds
D) Greater than 200 milliseconds
Correct answer: B
Explanation: Ventricular depolarization through the His–Purkinje system is normally under 120 milliseconds.

 

The corrected Q–T interval is clinically important because prolonged Q–T increases risk of:
A) Atrial flutter
B) Atrioventricular nodal reentry
C) Torsades de pointes
D) Sinus bradycardia
Correct answer: C
Explanation: Excess prolongation of repolarization predisposes to polymorphic ventricular tachycardia.

 

In two or more contiguous leads, new ST segment elevation most often suggests:
A) Hyperkalemia
B) Acute transmural myocardial injury
C) Normal early repolarization in all people
D) Lead misplacement every time
Correct answer: B
Explanation: ST segment elevation in anatomically related leads indicates current of injury from acute infarction (with exceptions such as pericarditis or early repolarization).

 

T wave inversion in anatomically contiguous leads most often indicates:
A) Ventricular paced rhythm
B) Myocardial ischemia or reperfusion change
C) Artifact
D) Normal finding in all adults
Correct answer: B
Explanation: Inversions can reflect subendocardial ischemia or evolving infarction patterns.

 

Leads V1 and V2 primarily view which region of the heart?
A) Inferior wall
B) High lateral wall
C) Septal region
D) Posterior wall exclusively
Correct answer: C
Explanation: V1–V2 are septal/right parasternal leads.

 

Which set of leads is considered inferior?
A) I, aVL
B) V1, V2
C) II, III, aVF
D) V5, V6
Correct answer: C
Explanation: Leads II, III, and aVF look at the inferior surface of the heart.

 

Which leads are classically lateral?
A) II, III, aVF
B) V1, V2
C) I, aVL, V5, V6
D) aVR only
Correct answer: C
Explanation: I, aVL (high lateral) and V5–V6 (low lateral) view the lateral left ventricle.

 

Which precordial leads are primarily anterior?
A) V3 and V4
B) V1 and V2
C) V5 and V6
D) aVR and aVL
Correct answer: A
Explanation: V3–V4 overly the anterior left ventricle.

 

Correct chest placement for lead V1 is at the:
A) Second intercostal space, right sternal border
B) Fourth intercostal space, right sternal border
C) Fifth intercostal space, midclavicular line
D) Fifth intercostal space, anterior axillary line
Correct answer: B
Explanation: V1 goes at the fourth right intercostal space; V2 mirrors on the left.

 

A normal frontal plane QRS axis in adults is approximately:
A) −90° to −30°
B) −30° to +90°
C) +90° to +180°
D) −180° to −90°
Correct answer: B
Explanation: Most adults have a QRS axis between −30 and +90 degrees.

 

Left axis deviation is commonly associated with:
A) Left anterior fascicular block
B) Right ventricular hypertrophy
C) Lateral myocardial infarction exclusively
D) Hypercalcemia
Correct answer: A
Explanation: Conduction delay in the left anterior fascicle shifts axis leftward.

 

Right axis deviation may be caused by:
A) Left ventricular hypertrophy
B) Right ventricular hypertrophy
C) Hyperthyroidism only
D) Low potassium
Correct answer: B
Explanation: Increased right ventricular forces direct the QRS vector rightward.

 

Right bundle branch block typically shows:
A) Broad notched R waves in I and V6
B) rsR′ pattern in V1 with a wide S wave in I and V6
C) Small R in V1 and tall R in V6 with narrow QRS
D) Diffuse low voltage only
Correct answer: B
Explanation: Delay in right ventricular depolarization creates the characteristic V1 “rabbit ears” and broad terminal S laterally.

 

Left bundle branch block typically shows:
A) Predominant S in V6
B) Broad, often notched R in I and V6 with deep S in V1
C) Narrow QRS
D) Tall R in V1
Correct answer: B
Explanation: Left-sided conduction delay produces wide, notched lateral R waves and deep V1 S.

 

Atrial fibrillation is characterized on electrocardiogram by:
A) Regular rhythm at 300 beats per minute with sawtooth waves
B) Irregularly irregular ventricular rhythm with no distinct P waves
C) Regular narrow-complex tachycardia with visible P before every QRS
D) Wide-complex rhythm with fusion beats
Correct answer: B
Explanation: Chaotic atrial activity leads to variable atrioventricular conduction and absent organized P waves.

 

Atrial flutter typically shows:
A) Sawtooth flutter waves at about 300 per minute with a regular conduction pattern
B) Chaotic baseline with no atrial activity
C) Wide-complex irregular rhythm
D) Only ST segment depression
Correct answer: A
Explanation: Typical flutter has organized atrial activity; ventricular response may be regular (often 2:1).

 

A regular narrow-complex tachycardia most consistent with reentry above the ventricles is called:
A) Ventricular tachycardia
B) Atrioventricular nodal reentry supraventricular tachycardia
C) Idioventricular rhythm
D) Torsades de pointes
Correct answer: B
Explanation: Reentry within or involving the atrioventricular node produces a fast, regular narrow-complex rhythm.

 

Features that favor ventricular tachycardia over supraventricular tachycardia with aberrancy include:
A) Narrow QRS and visible P before every QRS
B) Atrioventricular dissociation, capture or fusion beats, very wide QRS
C) Perfectly normal axis
D) Consistent preceding P waves
Correct answer: B
Explanation: These findings strongly suggest ventricular origin.

 

Torsades de pointes is most often associated with:
A) Short corrected Q–T interval
B) Prolonged corrected Q–T interval
C) Tall peaked T waves from high potassium
D) Hypercalcemia
Correct answer: B
Explanation: Prolonged repolarization predisposes to polymorphic twisting ventricular tachycardia.

 

Asystole appears on electrocardiogram as:
A) Wide irregular complexes without a pulse
B) A straight or nearly flat line without organized electrical activity
C) A regular narrow-complex tachycardia
D) Sawtooth waves
Correct answer: B
Explanation: Asystole is the absence of ventricular electrical activity.

 

Ventricular fibrillation appears as:
A) Regular narrow complexes at high rate
B) Organized atrial waves with dropped beats
C) Chaotic irregular waves with no identifiable QRS complexes
D) Sinus rhythm with premature beats
Correct answer: C
Explanation: Disorganized ventricular activation produces irregular, chaotic tracings.

 

First-degree atrioventricular block is defined by:
A) Progressive P–R prolongation with a dropped beat
B) P–R interval greater than 200 milliseconds with all P waves conducted
C) Some P waves not followed by QRS with constant P–R intervals
D) No relationship between P and QRS
Correct answer: B
Explanation: Conduction is delayed but not interrupted.

 

Second-degree atrioventricular block, Mobitz type I (Wenckebach), shows:
A) Fixed P–R intervals and dropped QRS complexes
B) Progressive P–R lengthening until a beat is dropped
C) No association between P and QRS
D) Very short P–R interval
Correct answer: B
Explanation: The hallmark is gradually increasing delay culminating in non-conduction.

 

Second-degree atrioventricular block, Mobitz type II, shows:
A) Progressive P–R prolongation
B) Constant P–R intervals with intermittent non-conducted P waves
C) No P waves present
D) Ventricular fibrillation
Correct answer: B
Explanation: Fixed conduction times with sudden failure of conduction define Mobitz II.

 

Third-degree (complete) atrioventricular block is characterized by:
A) Variable P–R intervals with dropped beats
B) Complete atrioventricular dissociation between P waves and QRS complexes
C) Short P–R interval with delta waves
D) Narrow-complex tachycardia
Correct answer: B
Explanation: Atria and ventricles beat independently due to absent conduction.

 

Hyperkalemia classically produces on electrocardiogram:
A) Tall peaked T waves and progressive QRS widening
B) Prominent U waves
C) Short Q–T interval with widened P waves
D) Atrial flutter
Correct answer: A
Explanation: High potassium accelerates repolarization (tall T) and depresses conduction (wide QRS).

 

Hypokalemia often produces:
A) Tall peaked T waves
B) Flattened T waves and prominent U waves
C) Marked QRS widening only
D) Delta waves
Correct answer: B
Explanation: Low potassium prolongs repolarization and reveals U waves.

 

Hypercalcemia typically causes:
A) Prolonged Q–T interval
B) Shortened Q–T interval
C) Widened QRS
D) Tall peaked T waves
Correct answer: B
Explanation: Calcium shortens the plateau phase, reducing Q–T duration.

 

Hypocalcemia typically causes:
A) Shortened Q–T interval
B) Prolonged Q–T interval
C) Tall peaked T waves
D) Delta waves
Correct answer: B
Explanation: Low calcium lengthens ventricular repolarization, prolonging Q–T.

 

The “scooped” ST segment with downsloping depression is characteristic of:
A) Severe hypothermia alone
B) Digoxin effect
C) Hyperkalemia
D) Pericarditis
Correct answer: B
Explanation: Digoxin produces a distinctive sagging ST segment.

 

Diffuse ST segment elevation with PR segment depression across many leads suggests:
A) Localized transmural infarction
B) Acute pericarditis
C) Right bundle branch block
D) Hyperkalemia
Correct answer: B
Explanation: Inflammation of the pericardium causes widespread current of injury and PR depression.

 

Electrocardiogram signs sometimes seen with acute pulmonary embolism include:
A) Left bundle branch block in all cases
B) Sinus tachycardia and right heart strain patterns (for example T wave inversion in V1–V3)
C) Universal ST elevation
D) Atrial flutter every time
Correct answer: B
Explanation: Tachycardia and signs of right ventricular strain may appear, though the tracing may be nonspecific.

 

In suspected right ventricular infarction with inferior changes, an additional useful lead is:
A) V3 left
B) V4 right (V4R)
C) aVR
D) aVL
Correct answer: B
Explanation: ST elevation in V4R supports right ventricular involvement.

 

Inferior wall myocardial infarction produces the most prominent changes in:
A) I and aVL
B) V1 and V2
C) II, III, and aVF
D) V5 and V6
Correct answer: C
Explanation: These leads look at the inferior surface.

 

A pathologic Q wave is generally defined as:
A) Any small initial negative deflection
B) Wider than 40 milliseconds and at least one quarter the height of the following R in that lead
C) Always present in healthy athletes
D) A tall positive deflection
Correct answer: B
Explanation: Significant Q waves suggest prior transmural infarction in that territory.

 

Electrical alternans (beat-to-beat QRS amplitude variation) is most classically associated with:
A) Hypercalcemia
B) Pericardial tamponade
C) Left bundle branch block
D) Hypokalemia
Correct answer: B
Explanation: Swinging of the heart in a large effusion can vary the recorded amplitude.

 

A functioning ventricular pacemaker often shows:
A) No evidence on the tracing
B) Small vertical pacer spikes before each QRS complex
C) Only ST depression
D) Tall P waves
Correct answer: B
Explanation: Artificial pacing stimuli appear as brief sharp spikes preceding captured complexes.

 

The “300–150–100–75–60–50” method for rate requires:
A) Measuring ten seconds only
B) Regular rhythm and large box counting between R waves
C) Counting P waves
D) Using a calculator
Correct answer: B
Explanation: Divide 300 by the number of large squares between R waves for regular rhythms.

 

Using the small-box method for heart rate, rate equals:
A) 1500 divided by the number of small squares between R waves
B) 300 divided by the number of small squares
C) 10 times the number of complexes in one second
D) 60 divided by large squares
Correct answer: A
Explanation: There are 1500 small squares per minute at standard speed.

 

A common source of electrocardiogram artifact that can mimic atrial activity is:
A) Paper speed
B) Skeletal muscle tremor or shivering
C) Very high blood pressure
D) Low body temperature only
Correct answer: B
Explanation: Muscle activity creates high-frequency noise that may imitate P waves.

 

Right and left arm lead reversal most often produces:
A) Inverted lead I with unexpected positive aVR
B) Tall R in V1
C) ST elevation in all leads
D) Atrial flutter
Correct answer: A
Explanation: Reversing arm electrodes reverses polarity of lead I and alters augmented limb leads.

 

In normal sinus rhythm, lead aVR typically shows:
A) Positive P, QRS, and T waves
B) Predominantly negative complexes
C) Flat line
D) Only pacer spikes
Correct answer: B
Explanation: aVR views the heart from the right shoulder; normal net vectors point away from it.

 

A simple quadrant method for axis uses:
A) Only precordial leads
B) The polarity of QRS in leads I and aVF
C) The size of the P wave in V1
D) The ST segment in V5
Correct answer: B
Explanation: Positive/negative combinations in I and aVF estimate the axis quadrant.

 

Sinus bradycardia is defined as:
A) Heart rate less than 100 beats per minute
B) Heart rate less than 60 beats per minute with sinus P before each QRS
C) Heart rate greater than 120 beats per minute
D) No P waves present
Correct answer: B
Explanation: The sinoatrial node sets a slow but regular rhythm.

 

Sinus tachycardia is defined as:
A) Heart rate greater than 100 beats per minute with normal P before each QRS
B) Narrow complex without P waves
C) Wide complex with fusion beats
D) No electrical activity
Correct answer: A
Explanation: Elevated sinus rate maintains organized atrial activation.

 

Respiratory sinus arrhythmia refers to:
A) Tachycardia during exhalation only
B) Normal variation in sinus rate with breathing
C) Atrial fibrillation
D) Ventricular bigeminy
Correct answer: B
Explanation: Vagal tone fluctuations with respiration alter sinus node discharge.

 

A junctional rhythm typically shows:
A) Tall P waves before each QRS
B) Absent or inverted P waves with narrow QRS and rate 40–60
C) Wide QRS with fusion beats
D) Sawtooth flutter waves
Correct answer: B
Explanation: The atrioventricular junction becomes the pacemaker; P waves may be absent or retrograde.

 

A premature atrial complex is recognized by:
A) An early, wide bizarre QRS
B) An early P wave of different shape followed by a normal or narrow QRS
C) No preceding P wave
D) Prolonged Q–T interval
Correct answer: B
Explanation: Ectopic atrial focus depolarizes the atria early with altered P morphology.

 

A premature ventricular complex is recognized by:
A) Early narrow QRS with normal P
B) Early wide bizarre QRS not preceded by a normal P and followed by a compensatory pause
C) Late narrow QRS
D) Only T wave inversion
Correct answer: B
Explanation: The beat originates in the ventricle and depolarizes myocardium slowly.

 

Bigeminy refers to:
A) Two P waves for every QRS
B) A repeating pattern of one premature beat followed by one normal beat
C) Alternating bundle branch block
D) Two QRS complexes fused into one
Correct answer: B
Explanation: The rhythm repeats in pairs (for example, normal beat then premature beat).

 

The Wolff–Parkinson–White pattern includes:
A) Very long P–R interval
B) Short P–R interval, slurred upstroke of QRS (delta wave), and wide QRS
C) Tall U waves
D) Negative P waves in all leads
Correct answer: B
Explanation: Accessory pathway preexcites the ventricle, shortening P–R and widening QRS.

 

Criteria often used for acute ST segment elevation myocardial infarction include new ST elevation of at least:
A) 0.25 millimeters in any lead
B) 1 millimeter in limb leads or 2 millimeters in precordial leads in two contiguous leads
C) 5 millimeters everywhere
D) 10 millimeters in aVR
Correct answer: B
Explanation: Thresholds differ by lead group; contiguity is key.

 

Non-ST elevation myocardial infarction is more commonly associated with:
A) Diffuse ST elevation
B) ST depression and/or T wave inversion in contiguous leads
C) Ventricular fibrillation only
D) Normal electrocardiogram in all cases
Correct answer: B
Explanation: Subendocardial ischemia often produces ST depression or T inversion.

 

A common voltage criterion for left ventricular hypertrophy (Sokolow–Lyon) is:
A) R in V6 plus S in V1 less than 10 millimeters
B) S in V1 plus R in V5 or V6 greater than 35 millimeters
C) R in aVL less than 7 millimeters
D) S in V2 greater than 10 millimeters
Correct answer: B
Explanation: High voltages reflect increased myocardial mass (interpretation depends on age and body habitus).

 

Right ventricular hypertrophy on electrocardiogram often shows:
A) Right axis deviation with R/S ratio greater than 1 in V1
B) Left axis deviation with tall R in V6
C) Very prolonged Q–T interval only
D) Diffuse low voltage
Correct answer: A
Explanation: Dominant right ventricular forces shift axis and precordial R/S patterns.

 

Left atrial enlargement is suggested by:
A) Peaked P waves in lead II
B) Broad, notched P in lead II and a biphasic negative terminal P in V1
C) Narrow P waves everywhere
D) Absence of P waves
Correct answer: B
Explanation: Prolonged left atrial activation widens and notches the P wave.

 

Right atrial enlargement is suggested by:
A) Very small P waves
B) Tall peaked P waves in inferior leads (>2.5 millimeters)
C) Negative P in V1
D) Absent P waves
Correct answer: B
Explanation: Increased right atrial mass produces high-amplitude P waves.

 

True or false: The QRS complex represents ventricular depolarization.
Correct answer: True
Explanation: Ventricular activation produces the QRS complex.

 

True or false: A small U wave can be normal, but a prominent U wave often suggests low potassium.
Correct answer: True
Explanation: Hypokalemia classically accentuates U waves.

 

True or false: The ST segment is normally elevated in most leads at rest.
Correct answer: False
Explanation: The ST segment is usually isoelectric; elevation or depression is abnormal unless due to benign early repolarization.

 

True or false: Atrial flutter always produces an irregular ventricular rhythm.
Correct answer: False
Explanation: Conduction is often a fixed ratio (for example, 2:1), yielding a regular rate.

 

True or false: Atrial fibrillation increases the risk of clot formation and stroke.
Correct answer: True
Explanation: Loss of effective atrial contraction promotes stasis and thrombus formation, especially in the left atrial appendage.

 

True or false: Ventricular fibrillation requires immediate defibrillation.
Correct answer: True
Explanation: It is a cardiac arrest rhythm that needs rapid shock.

 

True or false: Sinus rhythm implies an upright P in leads I and II with each P followed by a QRS at a consistent P–R interval.
Correct answer: True
Explanation: This pattern indicates sinoatrial origin with intact atrioventricular conduction.

 

True or false: Left bundle branch block can mask or mimic acute anterior ST elevation, complicating diagnosis.
Correct answer: True
Explanation: Secondary repolarization changes in left bundle branch block alter ST–T segments.

 

True or false: PR segment depression is a supportive electrocardiogram sign of acute pericarditis.
Correct answer: True
Explanation: Atrial current of injury can depress the PR segment.

 

True or false: Corrected Q–T accounts for heart rate to better estimate repolarization duration.
Correct answer: True
Explanation: Correction formulas adjust Q–T to a standardized rate.

 

True or false: Right axis deviation is commonly seen in chronic lung disease and right ventricular hypertrophy.
Correct answer: True
Explanation: Increased right-sided forces or pressure overload shift the axis.

 

True or false: Hyperkalemia is classically associated with tall peaked T waves.
Correct answer: True
Explanation: Rapid repolarization produces narrow, tall T waves early in hyperkalemia.

 

True or false: Asystole is a shockable rhythm that should be defibrillated immediately.
Correct answer: False
Explanation: Asystole is treated with high-quality cardiopulmonary resuscitation and medications; defibrillation is not indicated.

 

True or false: Pacemaker failure to capture appears as pacing spikes without subsequent P waves or QRS complexes.
Correct answer: True
Explanation: The stimulus is delivered but the myocardium does not depolarize.

 

True or false: Inferior myocardial infarction produces changes mainly in leads II, III, and aVF.
Correct answer: True
Explanation: These leads face the inferior wall.

 

True or false: Electrical axis cannot be determined from precordial leads alone using the quadrant method.
Correct answer: True
Explanation: The quadrant method uses frontal plane limb leads I and aVF.

 

True or false: Lead II records the potential of the left leg relative to the right arm.
Correct answer: True
Explanation: That vector aligns closely with the mean atrial and ventricular depolarization directions.

 

True or false: Lead aVR is usually predominantly positive during normal sinus rhythm.
Correct answer: False
Explanation: Net vectors usually point away from the right shoulder, making aVR negative.

 

True or false: Using the 300 rule to calculate rate assumes a regular rhythm.
Correct answer: True
Explanation: Large-box counting is valid when R–R intervals are consistent.

 

Fill in the blank: The P wave represents ____________________________ depolarization.
Correct answer: atrial
Explanation: It is the electrical activation of the atria.

 

Fill in the blank: The normal P–R interval is ____________________________ to ____________________________ milliseconds.
Correct answer: 120; 200
Explanation: Normal atrioventricular nodal conduction time is about 0.12–0.20 seconds.

 

Fill in the blank: The isoelectric segment between ventricular depolarization and repolarization is called the ____________________________ segment.
Correct answer: ST
Explanation: The ST segment begins at the J point and ends at the start of the T wave.

 

Fill in the blank: Lead V4 is placed at the ____________________________ intercostal space at the ____________________________ line.
Correct answer: fifth; midclavicular
Explanation: Correct precordial placement is essential for accurate interpretation.

 

Fill in the blank: A widened QRS complex is greater than ____________________________ milliseconds.
Correct answer: 120
Explanation: Duration ≥0.12 seconds indicates intraventricular conduction delay.

 

Fill in the blank: With the small-box method, heart rate equals 1500 divided by the number of ____________________________ between R waves.
Correct answer: small squares
Explanation: Standard paper speed is 25 millimeters per second (1500 small squares per minute).

Fill in the blank: Pathologic Q waves are ____________________________ seconds or more in duration and at least ____________________________ of the following R wave amplitude in that lead.
Correct answer: 0.04; one quarter
Explanation: Width and depth criteria suggest prior transmural necrosis.

Fill in the blank: A common voltage criterion for left ventricular hypertrophy is S in V1 plus R in V5 or V6 greater than ____________________________ millimeters.
Correct answer: 35
Explanation: This Sokolow–Lyon threshold suggests increased left ventricular mass.

 

Fill in the blank: In atrial fibrillation the ventricular rhythm is described as ____________________________.
Correct answer: irregularly irregular
Explanation: Variable atrioventricular conduction produces unpredictable R–R intervals.

 

Fill in the blank: The corrected Q–T interval adjusts the Q–T for the ____________________________ rate.
Correct answer: heart
Explanation: Correction accounts for the effect of rate on repolarization time.

 

Short answer: Describe how to calculate heart rate using the “300 rule,” and give an example.
Correct answer: Count the number of large boxes between consecutive R waves and divide 300 by that number; for example, 3 large boxes gives about 100 beats per minute.
Explanation: Paper speed is 25 millimeters per second (300 large boxes per minute).

 

Short answer: Explain why left bundle branch block complicates diagnosis of acute anterior myocardial infarction on the electrocardiogram.
Correct answer: Left bundle branch block causes secondary ST–T changes and wide QRS complexes that can mask or mimic ischemic ST elevation and Q waves, reducing specificity.
Explanation: Altered depolarization changes repolarization vectors.

 

Short answer: State two electrocardiogram features that favor ventricular tachycardia over supraventricular tachycardia with aberrancy.
Correct answer: Atrioventricular dissociation and capture or fusion beats; very wide QRS with extreme axis also supports ventricular tachycardia.
Explanation: These indicate ventricular origin of the rhythm.

 

Short answer: Give two electrocardiogram findings that support acute pericarditis.
Correct answer: Diffuse ST segment elevation (concave) with PR segment depression; reciprocal PR elevation in aVR.
Explanation: Inflammation affects the epicardium diffusely.

 

Short answer: Describe the standard limb lead electrode positions for a 12-lead electrocardiogram.
Correct answer: Right arm, left arm, and left leg electrodes form the limb leads (with a right leg ground); precordial V1–V6 are placed across the chest at standard landmarks.
Explanation: Correct placement is required for valid interpretation.

 

Short answer: What does “contiguous leads” mean when interpreting ST segment changes?
Correct answer: Leads that view the same or adjacent cardiac region (for example, II, III, aVF for inferior; V3–V4 for anterior; V5–V6, I, aVL for lateral).
Explanation: Changes in contiguous leads strengthen diagnostic significance.

 

Short answer: Name one common cause of electrocardiogram artifact and one way to reduce it.
Correct answer: Muscle tremor or patient movement; ask the person to relax, warm shivering patients, and ensure good electrode contact.
Explanation: Reducing noise improves tracing quality.

 

Short answer: Briefly describe the typical electrocardiographic evolution after a transmural myocardial infarction.
Correct answer: Hyperacute tall T waves, then ST elevation; development of pathologic Q waves; later T wave inversion with eventual resolution of ST elevation.
Explanation: These reflect evolving injury, necrosis, and recovery.

 

Short answer: What distinguishes first-degree from second-degree atrioventricular block?
Correct answer: First-degree has prolonged P–R with all beats conducted; second-degree has non-conducted P waves (Mobitz I with progressive prolongation; Mobitz II with fixed P–R and dropped beats).
Explanation: Conduction delay versus intermittent failure.

 

Short answer: When should right-sided precordial leads be obtained, and what can they reveal during inferior infarction?
Correct answer: Obtain when inferior ST elevation is present or right ventricular infarction is suspected; ST elevation in V4R indicates right ventricular involvement.
Explanation: Right ventricular infarction affects management (for example, preload).