Which of the following conditions would maintain a normal heart rate of 60-100 beats per minute?

A normal heart rate, defined as between 60-100 beats per minute, is typically influenced by the underlying cardiac rhythm. In the case of premature atrial contractions, the heart may experience occasional early beats originating in the atria, which can momentarily disrupt the rhythm but generally does not result in a sustained change to the heart rate. The overall rate can remain within the normal range, especially if the underlying rhythm is sinus rhythm and the premature contractions are infrequent.

In contrast, atrial fibrillation is characterized by an irregularly irregular rhythm, often leading to a variable heart rate that may exceed 100 beats per minute. Supraventricular tachycardia results in an elevated heart rate, usually above 100 beats per minute, due to the rapid electrical impulses occurring in the atria or atrioventricular node. Ventricular tachycardia is associated with even higher heart rates, typically exceeding 100 beats per minute, originating from the ventricles.

Therefore, premature atrial contractions allow for the potential of a normal heart rate since they do not necessarily lead to persistent tachycardia, whereas the other conditions are characterized by rhythms that result in elevated heart rates.