CCMA EKG Administration 2 — Questions and Answers

Question 1: What does the P wave on an ECG represent?

Ventricular depolarization
Atrial depolarization (Correct answer)
Ventricular repolarization
Atrial repolarization

Correct answer: Atrial depolarization

The P wave represents the electrical depolarization of the atria, which initiates atrial contraction.

The P wave is the first deflection on the ECG and represents atrial depolarization — the electrical signal that travels from the SA node through the atria, causing both atria to contract and push blood into the ventricles. Normal P wave duration is <0.12 seconds. Absent P waves may indicate atrial fibrillation. Inverted P waves may indicate a junctional rhythm. The PR interval (P wave + PR segment) represents conduction through the AV node and is normally 0.12–0.20 seconds.

Question 2: A heart rate of 52 beats per minute would be classified as:

Tachycardia
Normal sinus rhythm
Bradycardia (Correct answer)
Atrial fibrillation

Correct answer: Bradycardia

Bradycardia is defined as a resting heart rate below 60 beats per minute.

Normal adult heart rate range is 60–100 bpm. Bradycardia (<60 bpm) may be a normal finding in trained athletes or during sleep. Pathological bradycardia causes symptoms like fatigue, dizziness, syncope, and shortness of breath. Common causes include sick sinus syndrome, AV block, hypothyroidism, and certain medications (beta-blockers, calcium channel blockers). Tachycardia is HR >100 bpm. Atrial fibrillation (AFib) produces an irregularly irregular rhythm with absent P waves — it is not simply defined by rate.

Question 3: Which artifact on an ECG is caused by the patient's muscle movement or shivering?

Baseline wander
60-cycle (AC) interference
Somatic muscle artifact (Correct answer)
Lead reversal artifact

Correct answer: Somatic muscle artifact

Somatic muscle artifact is caused by voluntary or involuntary muscle movement (trembling, shivering, Parkinson's tremor) and appears as irregular, erratic baseline movement.

ECG artifacts degrade tracing quality: Somatic muscle artifact — caused by patient movement, shivering, tremor; appears as irregular, fuzzy interference; correct by asking patient to relax, use positioning aids, warm the room. AC/60-cycle interference — caused by nearby electrical equipment; appears as regular 60-Hz sine wave pattern; correct by checking lead connections and eliminating electrical sources. Baseline wander — caused by breathing, loose electrodes, or patient movement; appears as slow, wavy baseline drift; correct by ensuring proper electrode placement and clean, dry skin.

Question 4: On ECG graph paper, what does each small square represent in time?

0.04 seconds (Correct answer)
0.10 seconds
0.20 seconds
0.40 seconds

Correct answer: 0.04 seconds

On standard ECG graph paper run at 25 mm/sec, each small (1 mm) square equals 0.04 seconds (40 milliseconds) in the horizontal (time) axis.

Standard ECG paper runs at 25 mm/second. Time measurements: 1 small square = 1 mm = 0.04 seconds; 5 small squares = 1 large square = 0.20 seconds; 5 large squares = 1 second. Voltage (amplitude): 1 small square = 0.1 mV vertically; 10 small squares (1 large square) = 1.0 mV. These measurements are used to calculate intervals: PR interval (0.12–0.20 seconds = 3–5 small squares), QRS duration (<0.12 seconds = <3 small squares), QT interval (<0.44 seconds = <11 small squares at normal HR).

Question 5: Before applying ECG electrodes, the medical assistant should prepare the patient's skin by:

Applying a thick layer of electrode gel directly to unwashed skin
Cleaning the skin with alcohol, drying it, and clipping chest hair if necessary (Correct answer)
Using acetone to strip all oils from the skin
Applying lotion to improve electrode adhesion

Correct answer: Cleaning the skin with alcohol, drying it, and clipping chest hair if necessary

Skin preparation for ECG involves removing oils and dead skin cells with alcohol, ensuring the skin is dry, and clipping (not shaving) excessive chest hair to improve electrode contact.

Proper skin preparation for ECG electrode placement: (1) Clean each electrode site with an alcohol swab in a circular motion to remove oils, dead cells, and perspiration; (2) Allow to dry completely — wet skin causes poor adhesion and artifact; (3) Clip (do not shave) excessive chest hair with disposable scissors if present; (4) Do not apply lotion or cream (reduces adhesion); (5) If diaphoretic, dry thoroughly and apply electrodes quickly. Poor skin preparation is the most common cause of ECG artifact and suboptimal tracings.

Question 6: In a normal ECG, what does the QRS complex represent?

Atrial repolarization
Ventricular depolarization (Correct answer)
Atrial depolarization
Ventricular repolarization

Correct answer: Ventricular depolarization

The QRS complex represents ventricular depolarization — the electrical activation of the ventricles causing ventricular contraction (systole).

The QRS complex is normally 0.06–0.10 seconds (<3 small squares). It represents simultaneous depolarization of the right and left ventricles. A widened QRS (>0.12 seconds) indicates abnormal ventricular conduction such as bundle branch block. The Q wave is a small negative deflection; R wave is the positive deflection; S wave is the negative deflection after the R. Not all three components are always visible. Atrial repolarization occurs during the QRS complex and is obscured by it. Ventricular repolarization is represented by the T wave.

CCMA EKG Administration 2

What does the P wave on an ECG represent?