What parameter should concern the nurse the most in a patient taking digitalis?

A. Heart rate of 88 beats per minute and regular: This rate is within normal limits and does not indicate digitalis toxicity. Regular rhythm with a normal heart rate suggests stable cardiac function. B. Heart rate of 52 beats per minute and irregular: Digitalis can cause bradycardia and arrhythmias, making this finding concerning. A slow, irregular pulse may indicate early toxicity and requires immediate evaluation before administering further doses. C. Heart rate of 100 beats per minute and irregular: While an irregular rhythm warrants monitoring, the rate is not dangerously low. Tachyarrhythmias can occur with many conditions and are less indicative of digitalis toxicity than bradycardic rhythms. D. Heart rate of 60 beats per minute and regular: This rate is at the lower end of normal but still acceptable. It does not suggest impaired conduction or toxicity associated with digitalis use.