Sem1mini3 - ECG MCQ - Quiz & Trivia

1. The T Wave on an EKG represents:

Ventricular Depolarization

Ventricular Repolarization

Atrial Depolarization

Atrial Repolarization

Ventricular Systole

The T Wave on an EKG represents ventricular repolarization. This is the phase of the cardiac cycle where the ventricles relax and reset their electrical charge in preparation for the next contraction. During ventricular repolarization, the ventricular muscle cells recover from the depolarization phase and regain their resting state. This is reflected as a positive deflection on the EKG tracing.

Explanation

The T Wave on an EKG represents ventricular repolarization. This is the phase of the cardiac cycle where the ventricles relax and reset their electrical charge in preparation for the next contraction. During ventricular repolarization, the ventricular muscle cells recover from the depolarization phase and regain their resting state. This is reflected as a positive deflection on the EKG tracing.

2. The following image is an ECG trace from Lead I. Determine if the heart rate and duration of the PR interval and QT interval are within the normal ranges.

Heart rate

PR interval

QT interval

Normal Normal Normal

Normal Greater than normal Normal

Normal Normal Greater than normal

Bradycardia Normal Less than normal

Bradycardia Greater than normal Less than normal

Bradycardia Less than normal Normal

The heart rate, PR interval, and QT interval are all within the normal ranges.

Explanation

The heart rate, PR interval, and QT interval are all within the normal ranges.

3. Choose the answer choice below which most closely represents the heart rate of the ECG trace shown.

300 beats per minute

150 beats per minute

100 beats per minute

75 beats per minute

60 beats per minute

The ECG trace shown indicates a regular and consistent pattern of peaks and valleys. By counting the number of peaks within a minute, we can determine the heart rate. In this case, there are approximately 150 peaks, indicating a heart rate of 150 beats per minute.

Explanation

The ECG trace shown indicates a regular and consistent pattern of peaks and valleys. By counting the number of peaks within a minute, we can determine the heart rate. In this case, there are approximately 150 peaks, indicating a heart rate of 150 beats per minute.

4. What electrical event of the heart is NOT recorded on the standard 12-lead ECG trace?

Atrial depolarization

Atrial repolarization

Phase 2 of the ventricular action potential

Ventricular repolarization

Phase 4 of the ventricular action potential

Atrial repolarization is not recorded on the standard 12-lead ECG trace. This is because the electrical activity associated with atrial repolarization is masked by the much larger QRS complex, which represents the depolarization of the ventricles. The P wave on the ECG trace represents atrial depolarization, and the T wave represents ventricular repolarization. Phase 2 and phase 4 of the ventricular action potential are also represented on the ECG trace.

Explanation

Atrial repolarization is not recorded on the standard 12-lead ECG trace. This is because the electrical activity associated with atrial repolarization is masked by the much larger QRS complex, which represents the depolarization of the ventricles. The P wave on the ECG trace represents atrial depolarization, and the T wave represents ventricular repolarization. Phase 2 and phase 4 of the ventricular action potential are also represented on the ECG trace.

5. If there is a blockage between the AV node and the AV bundle, how will this affect the appearance of the EKG?

PR interval would be smaller

QRS interval would be shorter

There would be more P waves than QRS complexes

There would be more QRS complexes than P waves

The T wave would be absent

If there is a blockage between the AV node and the AV bundle, it means that the electrical signals from the atria are unable to pass through to the ventricles. This would result in the atria continuing to generate their own electrical signals, causing more P waves to appear on the EKG. However, since the signals are not reaching the ventricles, there would be fewer QRS complexes, which represent ventricular depolarization. Therefore, the correct answer is that there would be more P waves than QRS complexes.

Explanation

If there is a blockage between the AV node and the AV bundle, it means that the electrical signals from the atria are unable to pass through to the ventricles. This would result in the atria continuing to generate their own electrical signals, causing more P waves to appear on the EKG. However, since the signals are not reaching the ventricles, there would be fewer QRS complexes, which represent ventricular depolarization. Therefore, the correct answer is that there would be more P waves than QRS complexes.

6. The normal direction of the QRS complex in lead aVR results from the

Repolarization of the ventricular endocardial surface before the epicardial surface.

Depolarization of the ventricular septum before the left ventricular wall

Conduction delay caused by the AV-node

Wave of depolarization moving away from the positive electrode.

Depolarization of the right ventricle before the left ventricle.

The normal direction of the QRS complex in lead aVR is opposite to the direction of the QRS complex in the other leads. This is because lead aVR is placed on the right arm, which is in a position opposite to the other limb leads. Therefore, the wave of depolarization in lead aVR moves away from the positive electrode, resulting in an inverted QRS complex.

Explanation

The normal direction of the QRS complex in lead aVR is opposite to the direction of the QRS complex in the other leads. This is because lead aVR is placed on the right arm, which is in a position opposite to the other limb leads. Therefore, the wave of depolarization in lead aVR moves away from the positive electrode, resulting in an inverted QRS complex.

7. The figure below shows a ventricular action potential. Which of the numbered portions of the action potential most closely corresponds to the ST-segment on an ECG trace?

1

2

3

4

5

The ST-segment on an ECG trace represents the plateau phase of the ventricular action potential, which is when the ventricles are contracting and pumping blood. In the given figure, portion 3 closely corresponds to the ST-segment because it represents the plateau phase, where the membrane potential remains stable before repolarization occurs.

Explanation

The ST-segment on an ECG trace represents the plateau phase of the ventricular action potential, which is when the ventricles are contracting and pumping blood. In the given figure, portion 3 closely corresponds to the ST-segment because it represents the plateau phase, where the membrane potential remains stable before repolarization occurs.