QT Interval

Question 1

What does the QT interval represent?

Answer 1

All the electrical activity of one complete ventricular cycle (ventricular depolarization and repolarization)

This includes both the depolarization and repolarization phases of the ventricles.

Question 2

When does the QT interval begin and end?

Answer 2

Begins at the onset of the Q wave and ends as the T wave comes back to the baseline

If there is no Q wave, measurement begins with the R wave.

Question 3

What factors cause variation in the QT interval?

Answer 3

Age, sex, and heart rate

These factors can influence the length of the QT interval significantly.

Question 4

What is considered a short QT interval?

Answer 4

0.39 seconds (390 milliseconds) or less

This is applicable to both men and women.

Question 5

What is considered a prolonged QT interval for women?

Answer 5

0.46 seconds (460 milliseconds) or longer

This threshold is specific to women.

Question 6

What is considered a prolonged QT interval for men?

Answer 6

0.45 seconds (450 milliseconds) or longer

This threshold is specific to men.

Question 7

What can a long QT interval lead to?

Answer 7

Ventricular dysrhythmias and sudden cardiac arrest

These conditions pose significant health risks and require medical attention.