**Core Concept**
The question pertains to the pathophysiology of atrial fibrillation (AF), a common type of supraventricular tachycardia characterized by rapid and irregular heart rhythm. AF is often associated with underlying cardiac conditions, such as hypertension, coronary artery disease, and valvular heart disease.

**Why the Correct Answer is Right**
Atrial fibrillation occurs due to abnormal electrical activity in the atria, leading to uncoordinated and rapid atrial contractions. This results in a decrease in cardiac output and an increased risk of thromboembolic events. The correct answer is related to the pathophysiological mechanism of AF and its treatment.

**Why Each Wrong Option is Incorrect**
**Option A:** This is incorrect as it does not accurately describe the pathophysiology of atrial fibrillation. While AF may lead to a decrease in cardiac output, it is not the primary cause of the condition.
**Option B:** This option is also incorrect as it does not accurately describe the pathophysiology of atrial fibrillation. AF is not directly caused by an increase in cardiac output.
**Option C:** This option is incorrect as it does not accurately describe the pathophysiology of atrial fibrillation. AF is not directly caused by a decrease in cardiac contractility.

**Clinical Pearl / High-Yield Fact**
In patients with atrial fibrillation, the use of rate-control medications, such as beta-blockers and calcium channel blockers, can help to reduce symptoms and improve quality of life. However, rhythm-control medications, such as antiarrhythmic drugs, may be used in certain cases to restore a normal heart rhythm.

**Correct Answer: D.**