**Core Concept**
Restrictive cardiomyopathy (RCM) is a condition characterized by the stiffening of the heart muscle, making it difficult for the ventricles to fill with blood during diastole. This results in elevated filling pressures and impaired diastolic function, which can lead to symptoms of heart failure.

**Why the Correct Answer is Right**
The correct answer is related to the pathophysiology of RCM. In RCM, the filling pressure is indeed increased due to the stiffened heart muscle, which restricts the normal filling of the ventricles. Option **d) In early phase, systolic function is not impaired** is correct because RCM primarily affects diastolic function, and systolic function may be preserved in the early stages of the disease. This is in contrast to other forms of cardiomyopathy, such as dilated cardiomyopathy, where systolic function is impaired.

**Why Each Wrong Option is Incorrect**
**Option A:** Filling pressure is increased - This statement is true for RCM, but it's not the correct choice because we're looking for the false statement. In fact, this is one of the hallmarks of RCM.

**Option B:** Left ventricular hypertrophy - This is not a characteristic of RCM. In RCM, the heart muscle is stiffened, but it is not hypertrophied.

**Option C:** Heart failure is not predominantly right sided - This statement is false. In RCM, right-sided heart failure is more common than left-sided heart failure, especially in the early stages of the disease.

**Clinical Pearl / High-Yield Fact**
A key clinical feature of RCM is the presence of elevated filling pressures, which can lead to pulmonary congestion and peripheral edema. In addition, RCM is often associated with other conditions such as amyloidosis, sarcoidosis, and hemochromatosis.

**Correct Answer: D. In early phase, systolic function is not impaired**