A client with a history of rheumatic fever is diagnosed with mitral valve stenosis. The client has shortness of breath with exertion and fatigue. Which assessment finding warrants immediate intervention by the nurse?

A. A rapid, irregular heart rate (e.g., atrial fibrillation) is common in mitral valve stenosis due to atrial enlargement but does not necessarily require immediate intervention unless it leads to severe symptoms like syncope or stroke. B. Blood-tinged sputum could indicate pulmonary edema or pulmonary hypertension, both of which are serious complications of mitral valve stenosis. This finding warrants immediate intervention as it may signify acute heart failure or other critical complications requiring prompt treatment. D. Swollen feet and ankles are common signs of fluid retention in heart failure, but they do not require immediate intervention compared to the potential complications of atrial fibrillation.