Which of the following factors may NOT contribute to the increase of premature ventricular beats?

Digoxin toxicity is typically associated with a range of cardiac arrhythmias, but it is not commonly linked to the increase of premature ventricular beats in the same way as the other options. Concern regarding digoxin toxicity often includes symptoms such as bradycardia, various atrial arrhythmias, and even complete heart block rather than ventricular ectopic beats.

In contrast, anxiety can lead to heightened adrenergic activity, which may influence heart rhythm and increase the likelihood of premature beats. Electrolyte imbalance, particularly involving potassium and magnesium levels, can significantly affect cardiac electrical activity and contribute to the occurrence of premature ventricular contractions. Acute respiratory problems may lead to hypoxia or changes in blood gas levels, also influencing heart rhythm and increasing the potential for abnormal heartbeats.

The unique mechanism of action and typical effects of digoxin position it as less likely to specifically increase premature ventricular beats compared to the other factors mentioned.