## **Core Concept**
The question combines electrocardiography (ECG) and echocardiography findings to point towards a specific diagnosis. Low QRS voltage on an ECG can be associated with various conditions, including obesity, pericardial effusion, and infiltrative diseases. Left ventricular hypertrophy (LVH) on echocardiography indicates thickening of the left ventricular wall, often due to increased afterload or cardiac disease.

## **Why the Correct Answer is Right**
The correct answer, , is Amyloidosis. Amyloidosis is a condition characterized by the deposition of amyloid fibrils in various tissues, including the heart. This deposition leads to restrictive cardiomyopathy, where the heart muscle becomes stiff, and the ventricular walls become thickened. The amyloid deposits also affect the myocardium's electrical properties, resulting in low QRS voltage on the ECG. The combination of low QRS voltage on ECG with LVH on echocardiography is highly suggestive of cardiac amyloidosis.

## **Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because while obesity can cause low QRS voltage on ECG due to the attenuation of electrical signals by fatty tissue, it does not directly cause left ventricular hypertrophy as visualized on echocardiography in the context provided.
* **Option B:** This option is incorrect because although pericardial effusion can cause low QRS voltage on ECG, it typically does not cause LVH on echocardiography; instead, it might show a pericardial effusion.
* **Option C:** This option is incorrect as there is no commonly recognized condition directly linked to the combination of low QRS voltage and LVH in the provided choices that matches the description given for amyloidosis.

## **Clinical Pearl / High-Yield Fact**
A key clinical pearl is that cardiac amyloidosis can present with a unique combination of low QRS voltage on ECG and significant LVH on echocardiography, distinguishing it from other causes of LVH like hypertension or aortic stenosis, where QRS voltage is often high.

## **Correct Answer: D. Amyloidosis**