What is the definition of Paroxysmal Supraventricular Tachycardia (PSVT)?

• A. A type of irregular heartbeat caused by atrial flutter
• B. A regular, narrow-QRS tachycardia that starts or ends suddenly
• C. A rapid heart rate due to excretion of adrenaline
• D. A prolonged heart rate of over 180 bpm

Answer: (B)

Paroxysmal Supraventricular Tachycardia (PSVT) is characterized by a regular, narrow-QRS tachycardia that begins and ends abruptly. This definition captures the essential features of PSVT, where "paroxysmal" indicates that the episodes are intermittent and can occur suddenly, while "supraventricular" refers to the origin of the tachycardia being above the ventricles, typically involving the atria or the atrioventricular junction.

The terminology "narrow-QRS" signifies that the QRS complexes, which represent ventricular depolarization, are normal in width, indicating that the heart's electrical conduction pathway is functioning properly. This is relevant in PSVT as the tachycardia often involves a reentry circuit that does not compromise ventricular conduction.

In contrast, other options expand on different conditions or attributes that do not accurately characterize PSVT, such as an irregular heartbeat or a specific heart rate threshold without mentioning the rapid onset and termination of the episodes. This understanding is crucial for recognizing and managing PSVT effectively in clinical settings.