Question 1

The QT interval:

Accepted Answer

The QT interval represents the time from the start of ventricular depolarization to the end of ventricular repolarization and is typically between 0.36 and 0.44 seconds in duration.

Question 2

A prolonged QT interval:

Accepted Answer

A prolonged QT interval is an indicator of delayed ventricular repolarization, which can predispose individuals to life-threatening arrhythmias like Torsades de Pointes, not sinus tachycardia. Hypercalcemia actually shortens the QT interval, and while digoxin toxicity can affect the heart, it's more associated with other ECG changes. The definition of a prolonged QT can vary, but it's generally considered prolonged if over 440ms for men and 460ms for women, not strictly over 0.50 seconds.

Question 3

The U wave:

Accepted Answer

The U wave follows the T wave in the ECG cycle, representing afterpotentials from the ventricles. It is not always present, does not always deflect opposite of its associated QRS complex, and is typically smaller than the T wave.

Question 4

Prominent U waves are seen in:

Accepted Answer

Prominent U waves are typically associated with hypokalemia, which is a condition characterized by low potassium levels in the blood.

Question 5

The J point is not always easy to identify when assessing the ST segment. Sometimes you can identify it by looking for a small notch, slope, or other movement that suggests an alteration of electrical flow.

Accepted Answer

The answer of The J point is not always easy...

Question 6

To measure the T wave, identify its starting and ending point, then move to the center of the waveform. Next, count the number of small boxes between the isoelectric line and the top of the waveform.

Accepted Answer

To measure the T wave amplitude, you identify its starting and ending point, but you measure from the isoelectric line to the peak (highest or lowest point) of the T wave, not by moving to the center of the waveform. The counting of small boxes is done to measure the height or depth from the isoelectric line to the peak of the T wave, not from the center.

Question 7

T waves with bumps may be seen when P waves are buried in the T waves.

Accepted Answer

The answer of T waves with bumps may be seen...

Question 8

T waves seen with impulses that arise from the ventricles take the same direction as their associated QRS complexes.

Accepted Answer

The answer of T waves seen with impulses that arise...

Question 9

To measure the QT interval, first locate the isoelectric line immediately preceding the Q wave (or R wave if there is no Q wave). Next, locate the end of the T wave. Count the number of boxes in between these two points.

Accepted Answer

The answer of To measure the QT interval, first locate...

Quiz 9: ST Segments, T-Waves, QT Intervals, and U-Waves