Question 1

What is the electrical axis of the patient's heart if lead I is predominantly negative and lead aVF is predominantly positive?

Accepted Answer

The electrical axis of the heart is determined by the direction of the overall flow of electrical activity during depolarization. If lead I is predominantly negative and lead aVF is predominantly positive, it indicates that the electrical axis is pointing downward and to the right, which is consistent with right axis deviation.

Question 2

What does an ST elevation on a 12-lead ECG mean?

Accepted Answer

ST elevation on a 12-lead ECG indicates that there is significant and ongoing damage to the heart tissue. Immediate intervention is necessary to prevent further damage and potentially save the affected area of the heart. The tissue is not dead yet, but without intervention, it may become necrotic.

Question 3

To indicate myocardial ischemia, two anatomically contiguous leads must show the ST segment to be ________.

Accepted Answer

Myocardial ischemia is indicated by ST segment depression of at least 1 mm in two anatomically contiguous leads. ST segment elevation is typically indicative of myocardial infarction, rather than ischemia. Therefore, choices A and B are incorrect. A depression of at least 3 mm is more indicative of ST segment depression associated with a myocardial infarction, rather than ischemia. Therefore, choice D is also incorrect.

Question 4

In left ventricular hypertrophy, how does the QRS complex appear?

Accepted Answer

In left ventricular hypertrophy, the QRS complex appears taller and deeper than normal due to the increased muscle mass and therefore increased electrical activity in the left ventricle.

Question 5

Which of the following can cause extreme right axis deviation?

Accepted Answer

The answer of Which of the following can cause extreme...

Question 6

To determine the presence of left ventricular hypertrophy, which leads should you refer to?

Accepted Answer

Leads V1, V2, V5, and V6 are used to assess left ventricular hypertrophy by evaluating the R wave in V5 or V6 and the S wave in V1 or V2. The sum of these wave amplitudes is used in criteria like the Sokolow-Lyon index.

Question 7

When determining the electrical axis, which portion of the ECG tracing should you focus on?

Accepted Answer

The electrical axis is determined by analyzing the direction and magnitude of the QRS complex.

Question 8

You are analyzing a 12-lead ECG for the presence of left ventricular hypertrophy. After measuring carefully, you determine that the QS measurement is 12 mm and the R wave measurement is 20 mm. What does this patient have?

Accepted Answer

The Sokolow-Lyon criteria for left ventricular hypertrophy is met when the sum of the S wave in V1 and the R wave in V5 or V6 is greater than 35 mm. In this case, the sum is 32 mm (12 mm + 20 mm), which does not meet the criteria for left ventricular hypertrophy.

Question 9

If a patient has left ventricular hypertrophy, what type of axis deviation will be seen?

Accepted Answer

Left ventricular hypertrophy often leads to left axis deviation due to the increased mass and electrical activity of the left ventricle overpowering the right, altering the overall direction of the heart's electrical axis towards the left.

Question 10

When determining the presence of left ventricular hypertrophy, you measure to the tip of the deepest QS complex in V1 or V2 and to the tip of the tallest R wave in V5 or V6. For both of these measurements, where should you start the measurement?

Accepted Answer

The measurement for determining the presence of left ventricular hypertrophy should be taken from the isoelectric line, which is the baseline or flat line on an ECG tracing. This is because the height of the QRS complex is measured from the baseline, and both the deepest QS complex in V1 or V2 and the tallest R wave in V5 or V6 represent the tallest or deepest deviation from the baseline. Starting the measurement at any other point would not accurately reflect the height of the QRS complex or the presence of left ventricular hypertrophy.

Question 11

Ventricular hypertrophy occurs when the heart must exert more effort to maintain normal cardiac output. Why is this greater effort needed?

Accepted Answer

Increased peripheral vascular resistance means that the heart must work harder to pump blood against the increased resistance in the blood vessels, leading to hypertrophy of the ventricles.

Question 12

Right axis deviation is considered normal in which group of patients?

Accepted Answer

Right axis deviation (RAD) is considered normal in children and tall, thin adults. In these individuals, the electrical activity of the heart is oriented more towards the vertical axis (up and down), which can result in a deviation of the electrical axis towards the right side of the body. RAD can indicate an abnormality in other groups of patients, but in the absence of other signs or symptoms, it is typically not concerning in this group.

Question 13

In left ventricular hypertrophy, more electricity flows through the heart. In practical terms, how will the QRS complexes appear?

Accepted Answer

In left ventricular hypertrophy, the heart muscle of the left ventricle thickens, which means there's more muscle mass for the electrical current to travel through. This results in QRS complexes on an ECG that are taller and deeper than normal, reflecting the increased electrical activity required to depolarize the enlarged heart muscle.

Question 14

Which of the following is not a possible cause of left axis deviation?

Accepted Answer

The answer of Which of the following is not a...

Question 15

What is the term for an abnormal thickening of the ventricular wall due to chronic pressure overload that is often caused by hypertension?

Accepted Answer

Hypertrophy is the term for an abnormal thickening of the ventricular wall due to chronic pressure overload that is often caused by hypertension. Hyperpnea refers to an increase in breathing rate, while hyperkalemia refers to an excess of potassium in the blood. Hypertension is a contributing factor to hypertrophy but is not the term for the thickening itself.

Question 16

What is the electrical axis of the patient's heart if leads I and aVF are both predominantly negative?

Accepted Answer

When both leads I and aVF are predominantly negative, it indicates an extreme right axis deviation, also known as "northwest axis."

Question 17

When totaled, how many millimeters are necessary in V1 or V2 from the isoelectric line to the tip of the deepest QS complex, plus the distance from the isoelectric line to the tip of the tallest R wave in V5 or V6, to suspect left ventricular hypertrophy?

Accepted Answer

The Sokolow-Lyon criteria for left ventricular hypertrophy suggest that the sum of the S wave in V1 or V2 and the R wave in V5 or V6 should be greater than or equal to 35 mm.

Question 18

Which leads are used to determine the presence of axis deviation?

Accepted Answer

Leads I and aVF are used to determine the axis deviation in the frontal plane by observing the direction of the QRS complex. If the QRS complex is positive in both leads, the axis is normal. Deviations from this pattern indicate axis deviations.

Question 19

What is the electrical axis of the patient's heart if lead I is predominantly positive and lead aVF is predominantly negative?

Accepted Answer

Lead I being predominantly positive and lead aVF being predominantly negative are characteristic of left axis deviation.

Question 20

What is the electrical axis of the patient's heart if leads I and aVF are both predominantly positive?

Accepted Answer

Leads I and aVF are perpendicular to each other and if they are both positive or mostly positive, it indicates a normal axis.

Quiz 15: Basic 12-Lead Ecg Interpretation