An adult male is admitted with dyspnea on exertion, persistent cough, and palpitations. His telemetry reveals atrial fibrillation. Which additional assessment finding warrants the most immediate intervention by the nurse?

A. Respiratory rate of 22 breaths/minute: This rate is mildly elevated and may reflect exertional dyspnea or anxiety, but it does not indicate immediate respiratory distress. It requires monitoring but does not demand urgent intervention. B. Production of frothy, pink-tinged secretions: This finding is a hallmark of acute pulmonary edema and signals severe left-sided heart failure with fluid backing up into the alveoli. It compromises oxygenation and requires urgent intervention, such as diuretics and supplemental oxygen. C. Pitting edema of the ankles bilaterally: Pitting edema reflects chronic volume overload, often associated with right-sided heart failure. While concerning, it develops over time and is not as immediately life-threatening as pulmonary congestion with compromised gas exchange. D. Irregular apical heart rhythm: An irregular rhythm is consistent with atrial fibrillation and explains the palpitations, but it is a known condition in this case. Unless accompanied by hemodynamic instability, it does not demand immediate intervention on its own.