This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: C.V.S., Subject name: Medicine
A 60-year-old woman presents with symptoms of weight loss, anxiety, and palpitations. On examination, she has a thyroid goiter. Which of the following is the most likely cardiac finding? 
Select and explain. 
A. prolonged circulation time, B. decreased cardiac output, C. paroxysmal atrial fibrillation, D. pericardial effusion
C: paroxysmal atrial fibrillation
Answer: C: paroxysmal atrial fibrillation 
Explanation: Thyroid disease may affect the heart muscle directly or there may be excessive sympathetic stimulation. Common symptoms of thyrotoxic heart disease include palpitations, exertional dyspnea, and worsening angina. Atrial fibrillation is particularly common in older individuals.