CCT Electrocardiography Procedures & Interpretation — Questions and Answers

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

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

Correct answer: Atrial depolarization

On an electrocardiogram (ECG), the P wave represents atrial depolarization, which is the electrical activation of the atria. This electrical impulse originates in the SA node and spreads across the atrial muscle, causing it to contract. This atrial contraction pushes blood into the ventricles, initiating the cardiac cycle.

Question 2: What is the normal duration of the PR interval?

0.08 to 0.10 seconds
0.12 to 0.20 seconds (Correct answer)
0.20 to 0.28 seconds
0.30 to 0.40 seconds

Correct answer: 0.12 to 0.20 seconds

The PR interval on an ECG measures the time from the beginning of atrial depolarization (P wave) to the beginning of ventricular depolarization (QRS complex). A normal PR interval typically ranges from 0.12 to 0.20 seconds. This interval reflects the time it takes for the electrical impulse to travel from the atria, through the AV node, and into the ventricles.

Question 3: Which lead configuration is most commonly used in continuous monitoring?

Lead I
Lead II (Correct answer)
Lead III
aVR

Correct answer: Lead II

Lead II is the most commonly utilized lead configuration for continuous cardiac monitoring due to its optimal view of the heart's electrical activity. It typically provides the clearest and largest P waves and QRS complexes, making it easier to identify and analyze cardiac rhythms and detect arrhythmias. This clarity is crucial for accurate real-time assessment of heart function and prompt intervention if needed.

Question 4: Which artifact can be caused by patient movement?

60-cycle interference
Wandering baseline
Somatic tremor (Correct answer)
AC interference

Correct answer: Somatic tremor

Somatic tremor, also known as muscle artifact, appears on an ECG as irregular, jagged spikes or a fuzzy baseline. It is directly caused by involuntary or voluntary muscle contractions from the patient, such as shivering, talking, or movement during the recording. To minimize this artifact and ensure a clear tracing, it is crucial to ensure the patient is warm, comfortable, and relaxed.

Question 5: Which part of the ECG corresponds to ventricular depolarization?

T wave
P wave
QRS complex (Correct answer)
U wave

Correct answer: QRS complex

The QRS complex on an ECG represents ventricular depolarization, which is the electrical activation of the ventricles. This electrical event triggers the contraction of the ventricles, leading to the ejection of blood from the heart into the pulmonary artery and aorta. It is typically the largest and most prominent wave complex on the ECG due to the significant muscle mass of the ventricles.

Question 6: What is indicated by a prolonged QT interval?

Atrial flutter
Ventricular fibrillation
Increased arrhythmia risk (Correct answer)
Normal conduction

Correct answer: Increased arrhythmia risk

A prolonged QT interval on an ECG indicates a delay in ventricular repolarization, which is the electrical recovery phase of the ventricles. This extended recovery period makes the heart more vulnerable to developing dangerous ventricular arrhythmias, such as Torsades de Pointes. Therefore, a prolonged QT interval is a significant marker for an increased risk of sudden cardiac death and requires careful monitoring.

Question 7: Which ECG change is seen in hyperkalemia?

Flattened T waves
Peaked T waves (Correct answer)
ST segment depression
Prolonged PR interval

Correct answer: Peaked T waves

Hyperkalemia, an elevated level of potassium in the blood, significantly affects cardiac electrical activity. One of the classic and earliest ECG changes seen in hyperkalemia is the presence of tall, narrow, and 'peaked' T waves. As potassium levels rise further, other changes like a prolonged PR interval, widened QRS complex, and eventual asystole can occur, indicating severe cardiac compromise.

Question 8: Which action is most important when preparing a patient for a 12-lead ECG?

Ensure the patient eats a meal
Apply lotion to the chest
Shave or clean the electrode sites (Correct answer)
Use reusable electrodes

Correct answer: Shave or clean the electrode sites

Proper skin preparation is the most critical step when preparing a patient for a 12-lead ECG to ensure a high-quality tracing. Shaving excessive hair and thoroughly cleaning the skin with alcohol or abrasive gel removes dead skin cells, oils, and hair, which can impede electrical conduction. This meticulous preparation ensures optimal electrode contact and minimizes artifact, leading to a clear and accurate ECG recording.

Question 9: Which condition shows ST elevation on an ECG?

Stable angina
Myocardial infarction (Correct answer)
Pericarditis
Atrial fibrillation

Correct answer: Myocardial infarction

ST elevation on an ECG is a critical indicator of acute myocardial infarction (heart attack), specifically a STEMI (ST-elevation myocardial infarction). It signifies significant myocardial injury or ischemia, where a coronary artery is completely blocked, leading to a lack of blood flow to a portion of the heart muscle. Prompt recognition of ST elevation is crucial for immediate intervention to restore blood flow and minimize heart damage.

CCT Electrocardiography Procedures & Interpretation

What does the P wave represent in an ECG?