**Core Concept**
Chronic constrictive pericarditis (CCP) is a condition characterized by thickening and calcification of the pericardium, leading to impaired diastolic filling of the heart. This results from a combination of chronic inflammation and fibrosis, often secondary to previous pericarditis or tuberculosis.

**Why the Correct Answer is Right**
Chronic constrictive pericarditis leads to a reduction in the volume of blood that can be accommodated in the cardiac chambers during diastole. This is due to the rigid and non-compliant pericardium, which restricts the expansion of the heart. As a result, patients with CCP often present with signs of right-sided heart failure, including ascites, peripheral edema, and hepatomegaly. The increased pressure in the hepatic and inferior vena cava veins can also lead to an enlarged liver.

**Why Each Wrong Option is Incorrect**
**Option A:** Incorrect because while it is true that patients with CCP may have a decreased ejection fraction, it is not the most characteristic feature of this condition. The hallmark of CCP is impaired diastolic filling, not systolic dysfunction.

**Option B:** Incorrect because this statement is true. Patients with CCP often have a decreased cardiac output, which can lead to symptoms such as fatigue, weakness, and shortness of breath.

**Option C:** Incorrect because this statement is true. The pericardium in CCP is typically thickened and calcified, which can be visualized on imaging studies such as echocardiography or CT scans.

**Option D:** Incorrect because this statement is true. Patients with CCP often have a characteristic M-mode echocardiogram pattern, known as the "dip and plateau" or "square root sign," which reflects the restricted diastolic filling.

**Clinical Pearl / High-Yield Fact**
It is essential to differentiate CCP from restrictive cardiomyopathy, as the treatment approaches are distinct. While CCP is typically treated with pericardiectomy, restrictive cardiomyopathy may require medical therapy to manage symptoms and slow disease progression.

**Correct Answer: A.**