Professional and Linguistic Assessments Board (PLAB) Practice Exam

What might a prolonged QT interval indicate in a patient?

1. Electrolyte imbalance

2. Bradycardia

3. Tachycardia

4. Myocardial infarction

The correct answer is: Electrolyte imbalance

A prolonged QT interval can be a significant indicator of underlying health issues, particularly related to the heart's electrical system. It signifies delayed repolarization of the cardiac ventricles, which can lead to an increased risk of serious arrhythmias such as torsades de pointes. One of the most common causes of a prolonged QT interval is electrolyte imbalance, especially low levels of potassium (hypokalemia) or magnesium (hypomagnesemia). These electrolytes play crucial roles in cardiac function, and their deficiency disrupts the normal electrical conduction in the heart, leading to prolonged repolarization. In addition, various medications and congenital long QT syndromes can also cause the interval to extend. While bradycardia, tachycardia, and myocardial infarction may have their own implications on the heart's rhythm and health, they are not as directly associated with the specific phenomenon of a prolonged QT interval as electrolyte imbalances are. Understanding this relationship between the QT interval and electrolyte levels is essential for diagnosis and management in clinical practice.