Question 1
A patient who recently started taking a new antiarrhythmic medication comes in for a follow-up EKG. The medical assistant notes a QT interval spanning 0.52 seconds. Which of the following conclusions should the medical assistant draw from this tracing?
▸ Why C is the answer
The QT interval represents the total time for ventricular depolarization and repolarization. A normal QT interval is typically under 0.44 seconds, though it varies with heart rate. A measurement of 0.52 seconds is significantly prolonged. Option C is correct because a prolonged QT interval places the patient at a high risk for dangerous ventricular arrhythmias, such as Torsades de Pointes, requiring prompt provider notification. Option A is incorrect because this is a dangerous adverse effect of the medication, not a normal response. Option B is incorrect because the interval is lengthened, not shortened, and involves both depolarization and repolarization. Option D is incorrect because atrial conduction delays are reflected in the PR interval, not the QT interval. Recognizing this arrhythmia risk is essential for patient safety when monitoring medication effects.
🔑 Key takeaway
A prolonged QT interval increases the risk for lethal ventricular arrhythmias and requires prompt provider notification.

