Final answer:
The most likely ECG change in digoxin toxicity is an increased PR interval. Digoxin affects electrical activity, and toxicity can lead to several ECG abnormalities, including down-sloping ST segment depression and delayed atrioventricular conduction.
Step-by-step explanation:
The question you asked about ECG changes in digoxin toxicity focuses on identifying the most likely electrocardiogram (ECG) abnormalities associated with this condition. The correct answer to your question is: Increased PR interval.
Digoxin is a medication that can affect the electrical activity of the heart. When digoxin levels in the blood are too high, it can lead to toxicity, which may present with various ECG changes. A classic ECG finding in digoxin toxicity is a down-sloping ST segment depression, often referred to as a 'reverse tick' or 'Salvador Dali mustache' appearance. Though not listed in your choices, this is a distinctive feature of digoxin effect. Additionally, digoxin can cause an increased PR interval, which is reflective of delayed atrioventricular (AV) conduction.
Some other ECG manifestations of digoxin toxicity can include ventricular ectopy, such as ventricular extrasystoles, and atrial tachyarrhythmias with AV block. However, the most characteristic ECG change with digoxin toxicity is an increased PR interval, making A the best answer among your options.