A normal ECG shows a small positive deflection just before atrial systole begins. This wave most directly reflects:

A. atrial depolarization
B. atrial repolarization
C. ventricular depolarization
D. ventricular repolarization

A. atrial depolarization

In a healthy heart, the QRS complex is generated by:

A. atrial recovery potentials
B. AV nodal delay only
C. ventricular depolarization
D. ventricular relaxation only

C. ventricular depolarization

A normal T wave is produced when the ventricles:

A. begin isovolumic contraction
B. undergo rapid depolarization
C. are fully polarized
D. repolarize

D. repolarize

During ventricular depolarization, how does the electrical charge across the cell membrane change?

A. Inside negative, outside positive
B. Both surfaces negative
C. Inside positive, outside negative
D. Both surfaces positive

C. Inside positive, outside negative

The normal monophasic action potential of ventricular muscle lasts about:

A. 0.25 to 0.35 second
B. 0.05 to 0.10 second
C. 0.40 to 0.50 second
D. 0.10 to 0.15 second

A. 0.25 to 0.35 second

The ventricular T wave normally occurs approximately how long after ventricular depolarization?

A. 0.05 to 0.10 second
B. 0.25 to 0.35 second
C. 0.45 to 0.55 second
D. 0.15 to 0.20 second

B. 0.25 to 0.35 second

No potential is recorded on the ECG when ventricular muscle is:

A. partly polarized only
B. partly depolarized only
C. neither polarized nor depolarized
D. completely polarized or depolarized

D. completely polarized or depolarized

The P wave occurs at the beginning of contraction of the:

A. ventricles
B. Purkinje system
C. AV junction
D. atria

D. atria

The QRS complex occurs at the beginning of contraction of the:

A. atria
B. ventricles
C. SA node
D. great vessels

B. ventricles

The ventricles normally remain contracted until after the end of the:

A. P wave
B. PR interval
C. QRS complex
D. T wave

D. T wave

Atrial repolarization usually occurs approximately how long after termination of the P wave?

A. 0.15 to 0.20 second
B. 0.25 to 0.35 second
C. 0.40 to 0.50 second
D. 0.05 to 0.10 second

A. 0.15 to 0.20 second

The atrial repolarization wave is usually not seen because it is obscured by the larger:

A. P wave
B. T wave
C. QRS complex
D. U wave

C. QRS complex

The atrial repolarization wave is also called the:

A. atrial Q wave
B. atrial T wave
C. atrial U wave
D. atrial S wave

B. atrial T wave

Standard ECG paper runs at a speed of:

A. 10 mm/sec
B. 50 mm/sec
C. 25 mm/sec
D. 100 mm/sec

C. 25 mm/sec

On standard ECG paper, each 5-mm segment represents:

A. 0.04 second
B. 0.20 second
C. 0.10 second
D. 0.50 second

B. 0.20 second

Which statement best explains why the ECG is electrically silent during fully uniform ventricular depolarization?

A. no current gradient exists
B. all fibers are negative
C. atria cancel ventricular forces
D. Purkinje fibers stop conducting

A. no current gradient exists

On standard ECG paper run at 25 mm/sec, each small 1-mm box represents:

A. 0.02 second
B. 0.04 second
C. 0.10 second
D. 0.20 second

B. 0.04 second

The interval from the beginning of the P wave to the beginning of the QRS complex is the:

A. Q-T interval
B. S-T interval
C. R-R interval
D. P-Q interval

D. P-Q interval

The normal P-Q interval is closest to:

A. 0.16 second
B. 0.08 second
C. 0.35 second
D. 0.83 second

A. 0.16 second

The interval representing ventricular contraction, measured from the beginning of Q (or R if Q absent) to the end of T, is the:

A. P-Q interval
B. S-T segment
C. Q-T interval
D. R-R interval

C. Q-T interval

The normal Q-T interval is approximately:

A. 0.16 second
B. 0.83 second
C. 0.20 second
D. 0.35 second

D. 0.35 second

In a normal adult, the interval between two successive QRS complexes is closest to:

A. 0.83 second
B. 0.35 second
C. 0.16 second
D. 0.04 second

A. 0.83 second

A patient has an R-R interval of about 0.83 second. The heart rate is closest to:

A. 60 beats/min
B. 72 beats/min
C. 90 beats/min
D. 110 beats/min

B. 72 beats/min

When one portion of the ventricles depolarizes before the rest, that depolarized region becomes relatively:

A. electropositive
B. electrically neutral
C. electronegative
D. isoelectric

C. electronegative

During ventricular depolarization, current flows from the depolarized area toward the:

A. polarized area
B. AV node
C. septal base
D. atrial myocardium

A. polarized area

The cardiac impulse first arrives in the ventricles in the:

A. apex
B. free wall
C. base
D. septum

D. septum

Shortly after first entering the septum, the impulse next spreads to the:

A. epicardial surfaces first
B. papillary muscles
C. inner ventricular surfaces
D. outer ventricular surfaces

C. inner ventricular surfaces

If all ventricular current vectors are averaged algebraically early in depolarization, negativity is directed toward the:

A. apex
B. base
C. left arm
D. sternum

B. base

In that same averaged vector, positivity is directed toward the:

A. base
B. septum
C. right atrium
D. apex

D. apex

An electrode placed nearer the base of the heart during this phase would record as relatively:

A. negative
B. positive
C. biphasic
D. isoelectric

A. negative

An electrode placed nearer the apex of the heart during this phase would be relatively:

A. negative
B. positive
C. neutral
D. delayed

B. positive

With one electrode near the base and one near the apex under these conditions, the ECG meter will show a:

A. negative deflection
B. isoelectric baseline
C. positive deflection
D. widened QRS

C. positive deflection

A standard limb lead is recorded with the negative electrode on the right arm and the positive electrode on the left arm. Which lead is this?

A. Lead I
B. Lead II
C. Lead III
D. aVL

A. Lead I

A patient’s ECG lead has a negative electrode on the right arm and a positive electrode on the left leg. Which lead is being recorded?

A. Lead I
B. Lead III
C. aVF
D. Lead II

D. Lead II

In standard limb lead III, the negative terminal is attached to the:

A. right arm
B. left arm
C. right leg
D. left leg

B. left arm

Simultaneous recording of all three standard limb leads shows that Lead I plus Lead III equals:

A. aVR
B. aVL
C. Lead II
D. aVF

C. Lead II

Einthoven’s law states that the sum of the potentials in leads I and III equals the potential in:

A. Lead II
B. Lead I
C. aVF
D. Lead III

A. Lead II

How many standard chest leads are usually recorded from the anterior chest wall?

A. Four
B. Five
C. Eight
D. Six

D. Six

A normal ECG shows a predominantly negative QRS in a chest lead placed near the base of the heart. Which lead pair most fits this pattern?

A. V5 and V6
B. V1 and V2
C. V3 and V4
D. aVL and aVF

B. V1 and V2

Why are the QRS complexes in V1 and V2 usually mainly negative in a normal heart?

A. They face the left ventricle
B. They overlie the apex
C. They are near the base
D. They record atrial repolarization

C. They are near the base

In a normal ECG, the chest leads with mainly positive QRS complexes because they are nearer the apex are:

A. V4 V5 V6
B. V1 V2 V3
C. V2 V3 V4
D. V3 V5 V6

A. V4 V5 V6

A chest electrode is placed farther leftward and more apically, producing a mainly positive QRS in a normal patient. Which lead is most likely?

A. V1
B. V2
C. V3
D. V5

D. V5

In an augmented unipolar limb lead, a positive terminal on the left arm produces:

A. aVR
B. aVL
C. aVF
D. Lead I

B. aVL

Which augmented limb lead has its positive electrode on the left leg?

A. aVR
B. aVL
C. aVF
D. Lead III

C. aVF

A positive electrode placed on the right arm creates which augmented limb lead?

A. aVR
B. aVL
C. aVF
D. Lead II

A. aVR

Which augmented limb lead is classically inverted in the normal ECG?

A. aVL
B. aVF
C. Lead I
D. aVR

D. aVR

A student says all augmented limb leads are upright because they are “positive leads.” Which lead is the classic exception?

A. aVF
B. aVR
C. aVL
D. Lead II

B. aVR

A patient has brief palpitations and near-syncope that occur unpredictably during routine daily activities, but the office ECG is normal. The most appropriate next test is:

A. Signal-averaged ECG
B. Exercise treadmill only
C. Ambulatory ECG monitoring
D. Elective catheter ablation

C. Ambulatory ECG monitoring

Ambulatory ECG monitoring is most useful when symptoms are suspected to result from:

A. transient arrhythmias
B. chronic valvular stenosis
C. fixed coronary anatomy
D. stable heart failure

A. transient arrhythmias

A Holter monitor is prescribed because symptoms occur outside the clinic while the patient is walking around normally. This form of ECG monitoring is called:

A. stress ECG
B. vectorcardiography
C. signal averaging
D. ambulatory ECG monitoring

D. ambulatory ECG monitoring