Basic Electrocardiogram 1 — Questions and Answers

Question 1: When treating atrial fibrillation, which of the following is NOT a rate-controlling medication?

Amlodipine (Correct answer)
Metoprolol
Diltiazem
Digoxin

Correct answer: Amlodipine

Amlodipine is a dihydropyridine calcium channel blocker primarily used to treat hypertension and angina, and it does not significantly affect heart rate. Metoprolol (beta-blocker), Diltiazem (non-dihydropyridine calcium channel blocker), and Digoxin are all commonly used medications that slow the ventricular rate in atrial fibrillation by affecting AV nodal conduction.

Question 2: On the ECG trace below, which rhythm is present?

Second degree heart block
Junctional escape rhyhm
Sinus Rhythm
First degree heart block (Correct answer)

Correct answer: First degree heart block

First-degree heart block is characterized by a prolonged PR interval (greater than 0.20 seconds) on an ECG, indicating a delay in electrical conduction from the atria to the ventricles through the AV node. Despite the delay, every P wave is followed by a QRS complex, meaning all atrial impulses are eventually conducted. This consistent but extended delay is the hallmark of first-degree AV block.

Question 3: In a patient with a history of known AF, what would NOT be a cause of slow atrial fibrillation?

Digoxin
Thyrotoxicosis (Correct answer)
Complete Heart Block
Metroprolol

Correct answer: Thyrotoxicosis

Thyrotoxicosis, or hyperthyroidism, is known to *increase* heart rate and can often precipitate or exacerbate atrial fibrillation, leading to a *fast* ventricular response. Conversely, medications like Digoxin and Metoprolol are used to *slow* the ventricular rate in AF, and Complete Heart Block would also result in a slow ventricular rate, often independent of the atrial fibrillation.

Question 4: Which way does lead II go on an ECG?

90 degrees
0 degrees
30 degrees
60 degrees (Correct answer)

Correct answer: 60 degrees

In the standard limb lead configuration (Einthoven's triangle), Lead II is an inferior lead that runs from the right arm (negative) to the left leg (positive). It is oriented at an angle of +60 degrees on the frontal plane, making it a crucial lead for assessing the heart's electrical axis and inferior wall changes.

Question 5: Which antiemetics would NOT cause the QT interval to lengthen?

Domperidone
Ondansetron
Metoclopramide (Correct answer)
Droperidol

Correct answer: Metoclopramide

Metoclopramide, while having some potential for neurological side effects, is generally not associated with significant QT interval prolongation. In contrast, Domperidone, Ondansetron, and Droperidol are well-known to carry a risk of dose-dependent QT prolongation, which can predispose patients to serious ventricular arrhythmias like Torsades de Pointes.

Question 6: Which of the following rhythm's origins is most likely?

Ventricle
Sinus node
Atria (Correct answer)
AV node

Correct answer: Atria

Rhythms originating in the atria, such as atrial fibrillation, atrial flutter, or premature atrial contractions, are characterized by distinct atrial activity (e.g., fibrillatory waves, flutter waves, or premature P waves) and typically a narrow QRS complex. This indicates that the electrical impulse originates above the ventricles, specifically within the atria.

Question 7: Which of the following has the lowest chance of causing atrial fibrillation to occur?

Pulmonary embolism
Pericardial effusion (Correct answer)
Myocardial infarction
Mitral stenosis

Correct answer: Pericardial effusion

Pericardial effusion, an accumulation of fluid around the heart, primarily affects ventricular filling and can lead to tamponade, but it is less directly associated with the electrical instability that causes atrial fibrillation. Pulmonary embolism, myocardial infarction, and mitral stenosis are all significant stressors on the atria or can cause atrial enlargement and pressure changes, making them much more common causes or triggers for atrial fibrillation.

Basic Electrocardiogram 1

When treating atrial fibrillation, which of the following is NOT a rate-controlling medication?