Which arrhythmia is characterized by the absence of P-waves?

The absence of P-waves in an ECG trace is a key feature of junctional rhythms. In junctional rhythms, the electrical impulse originates from the AV node rather than the SA node, which is responsible for generating atrial depolarization and the corresponding P-waves. When the impulse starts at the AV node, it may bypass the atria or cause them to depolarize in a retrograde manner, often leading to little or no visible P-wave activity on the ECG.

In contrast, supraventricular tachycardia typically presents with narrowed QRS complexes and often maintains P-waves, albeit they may be obscured or inverted due to rapid heart rates. Ventricular tachycardia is characterized primarily by wide QRS complexes and can have absent P-waves, but it originates from the ventricles rather than the junctional area, which is a distinct characteristic that differentiates it from junctional rhythm. Sinus rhythm, on the other hand, is defined by the presence of regular P-waves, indicating normal atrial depolarization initiated by the SA node.

Thus, junctional rhythm is precisely defined by the lack of P-waves due to its origin in the AV junction, making it the correct answer