Block 3 EKG Strips And Stuff

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 after contracting during ventricular depolarization. The T wave is a positive deflection on the EKG graph that indicates the repolarization of the ventricles. This is an important part of the cardiac cycle as it allows the heart to prepare for the next contraction.

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 after contracting during ventricular depolarization. The T wave is a positive deflection on the EKG graph that indicates the repolarization of the ventricles. This is an important part of the cardiac cycle as it allows the heart to prepare for the next contraction.

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 is within the normal range, the PR interval is normal, and the QT interval is also normal.

Explanation

The heart rate is within the normal range, the PR interval is normal, and the QT interval is also normal.

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 correct answer is 150 beats per minute. This is because the ECG trace shows a regular pattern of peaks and valleys, indicating a consistent heart rate. By counting the number of peaks within a minute, it can be determined that the heart rate is approximately 150 beats per minute.

Explanation

The correct answer is 150 beats per minute. This is because the ECG trace shows a regular pattern of peaks and valleys, indicating a consistent heart rate. By counting the number of peaks within a minute, it can be determined that the heart rate is approximately 150 beats per minute.

4. 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 signal from the atria is unable to pass through to the ventricles. As a result, the atria will continue to generate their own electrical signals, causing more P waves to appear on the EKG. However, since the signal is unable to reach the ventricles, there will 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 signal from the atria is unable to pass through to the ventricles. As a result, the atria will continue to generate their own electrical signals, causing more P waves to appear on the EKG. However, since the signal is unable to reach the ventricles, there will be fewer QRS complexes, which represent ventricular depolarization. Therefore, the correct answer is that there would be more P waves than QRS complexes.

5. 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 limb leads. This is because lead aVR is a unipolar lead that is oriented towards the right arm, which acts as the positive electrode. Therefore, the QRS complex in lead aVR represents a wave of depolarization moving away from the positive electrode, resulting in a negative deflection.

Explanation

The normal direction of the QRS complex in lead aVR is opposite to the direction of the QRS complex in the other limb leads. This is because lead aVR is a unipolar lead that is oriented towards the right arm, which acts as the positive electrode. Therefore, the QRS complex in lead aVR represents a wave of depolarization moving away from the positive electrode, resulting in a negative deflection.

6. 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. The ECG primarily measures the electrical activity of the heart's chambers, specifically the depolarization and repolarization of the ventricles. Atrial repolarization occurs at the same time as ventricular depolarization, so it is not easily distinguishable on the ECG. However, atrial depolarization is recorded as the P wave, ventricular repolarization is recorded as the T wave, and phase 2 and phase 4 of the ventricular action potential are reflected in the QRS complex and ST segment, respectively.

Explanation

Atrial repolarization is not recorded on the standard 12-lead ECG trace. The ECG primarily measures the electrical activity of the heart's chambers, specifically the depolarization and repolarization of the ventricles. Atrial repolarization occurs at the same time as ventricular depolarization, so it is not easily distinguishable on the ECG. However, atrial depolarization is recorded as the P wave, ventricular repolarization is recorded as the T wave, and phase 2 and phase 4 of the ventricular action potential are reflected in the QRS complex and ST segment, respectively.

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. This is the phase where the ventricles are fully depolarized and contracted. In the given figure, portion 3 corresponds to the plateau phase, as it shows a sustained depolarization. Therefore, portion 3 most closely corresponds to the ST-segment on an ECG trace.

Explanation

The ST-segment on an ECG trace represents the plateau phase of the ventricular action potential. This is the phase where the ventricles are fully depolarized and contracted. In the given figure, portion 3 corresponds to the plateau phase, as it shows a sustained depolarization. Therefore, portion 3 most closely corresponds to the ST-segment on an ECG trace.