EKG and Cardiovascular Testing — practice questions

4% of the exam ≈6 real questions 6 free questions here

6 scored items — small, but almost entirely memorization. Lead placement, standard calibration, what each waveform represents, and which artifacts come from which cause.

Where people lose points

• Precordial leads are placed by anatomical landmark, not by eye. V1 and V2 sit at the fourth intercostal space, V4 at the fifth midclavicular — and V3 goes between V2 and V4, so V4 must be placed before V3.
• Standard settings are 25 mm/sec paper speed and 10 mm/mV calibration. A question describing an unusually tall or wide tracing is usually testing whether you check calibration first.
• Artifacts have distinct signatures: a wandering baseline suggests movement or loose electrodes, fine irregular spikes suggest muscle tremor, and uniform fine oscillation suggests AC interference.
• A medical assistant records the tracing and reports it. Interpreting a rhythm for the patient is outside scope — but recognizing lethal rhythms that need immediate escalation is expected.
• Skin preparation is part of the procedure, not optional. Oil, lotion and hair prevent good electrode contact and produce artifact.

Questions and answers, explained

All 5 questions above, with the correct answer and why it is correct. Everything here is on ekg and cardiovascular testing.

1. A medical assistant is applying the precordial (chest) electrodes for a 12-lead EKG. Where is the V1 electrode placed?

   • AFourth intercostal space at the right sternal borderCorrect
   • BFourth intercostal space at the left sternal border
   • CFifth intercostal space at the left midclavicular line
   • DSecond intercostal space at the right sternal border

   Why: Under the AHA standardized 12-lead system, V1 sits in the fourth intercostal space at the right sternal border. The closest distractor, the fourth intercostal space at the left sternal border, is V2 — the mirror position — and swapping the two produces a tracing that can falsely suggest septal abnormality. V4 is the fifth intercostal space at the left midclavicular line.

   Reference Domain 3F, k153; AHA standardized 12-lead ECG electrode placement

2. What are the standard paper speed and calibration (gain) settings for a diagnostic 12-lead EKG?

   • A50 mm/second and 10 mm/mV
   • B25 mm/second and 5 mm/mV
   • C10 mm/second and 25 mm/mV
   • D25 mm/second and 10 mm/mVCorrect

   Why: The standard diagnostic EKG is recorded at 25 mm/second with a gain of 10 mm/mV, so a 1 mV signal produces a 10 mm standardization mark. Doubling the paper speed to 50 mm/second (A) is sometimes used to separate closely spaced complexes, and half standardization (5 mm/mV) is used when complexes overlap, but any nonstandard setting must be documented on the tracing or measurements will be misread.

   Reference Domain 3F, k157; AHA/ACCF/HRS recommendations for standardization of the electrocardiogram

3. Which EKG component represents ventricular repolarization, the recovery phase of the ventricles?

   • AP wave
   • BQRS complex
   • CPR interval
   • DT waveCorrect

   Why: The T wave represents repolarization of the ventricles. The closest distractor, the QRS complex, is the opposite event — ventricular depolarization, which normally measures less than 0.12 second. Recognizing which component is which lets the medical assistant produce and label a technically correct tracing; interpreting the tracing remains the provider's responsibility.

   Reference Domain 3F, k156; AHA/ACCF/HRS ECG standardization

4. A male patient has dense chest hair over the V3 and V4 sites. How should the medical assistant prepare the skin?

   • APress each electrode down firmly and hold it in place for 30 seconds
   • BClip the hair at the electrode sites, cleanse the skin with alcohol, and let it dry completelyCorrect
   • CApply extra conductive gel on top of the hair
   • DMove V3 and V4 to hair-free skin higher on the chest

   Why: Hair blocks gel-to-skin contact and raises impedance, so the site is clipped, cleansed with alcohol to remove skin oils, and allowed to dry completely before the electrode is applied. The closest distractor, moving the electrodes to hair-free skin, changes the anatomic landmarks and invalidates the tracing — precordial positions are fixed and never relocated for convenience.

   Reference Domain 3F, k150 and k152; AHA practice standards for electrocardiography — skin preparation

5. A tracing shows regular P waves at about 80 per minute and regular QRS complexes at about 35 per minute, with no consistent relationship between them. This pattern is characteristic of which finding?

   • ASinus bradycardia
   • BAtrial fibrillation
   • CThird-degree (complete) heart blockCorrect
   • DSomatic tremor artifact

   Why: In third-degree heart block the atria and ventricles beat completely independently (AV dissociation): the P waves march through at their own regular rate while a slow escape rhythm drives the ventricles, and the PR interval is not constant. This is a medical emergency and must be reported to the provider immediately. The closest distractor, sinus bradycardia, is also slow but every P wave is followed by a QRS at a constant PR interval. Atrial fibrillation (B) has no discrete P waves at all and an irregularly irregular ventricular response.

   Reference Domain 3F, k155; AHA/ACC criteria for third-degree AV block

Topics inside this domain

• Medical assistant scope of practice
• Specimen labeling and patient identification

Drill other domains

• Foundational Knowledge and Basic Science (10%)
• Anatomy and Physiology (5.3%)
• Patient Intake and Vitals (9.3%)
• General Patient Care (18.7%)
• Infection Control and Safety (10%)
• Point of Care Testing and Laboratory Procedures (6%)

← Back to the full practice exam