A characteristic of non-conducted PAC is that?

A premature atrial contraction (PAC) is characterized by early P-waves that can sometimes occur in close proximity to the preceding T-wave of the previous beat. In non-conducted PACs, the electrical impulse does not conduct to the ventricles, meaning that although a P-wave is present, it does not lead to a subsequent QRS complex. When this occurs, the P-wave can often be visually obscured or "buried" within the T-wave of the preceding beat. This phenomenon of a P-wave occurring in the T-wave is a distinctive feature of non-conducted PAC and helps in identifying this type of arrhythmia on an electrocardiogram.

The incorrect options highlight different aspects of PACs or cardiac physiology that do not specifically apply to non-conducted PACs, such as the presence of frequent QRS complexes or consistently elevated heart rates, which would not be characteristic of a non-conducted PAC. Instead, a non-conducted PAC would specifically lack a corresponding QRS due to the impulse not effectively conducting to the ventricles.