**Core Concept:** Electrocardiography (ECG) is an important diagnostic tool used to assess cardiac electrical activity and detect abnormalities that may indicate cardiac pathology. In the context of the question, we are considering the ECG findings in an elderly patient with hypertension.

**Why the Correct Answer is Right:**

The correct answer, **D**: "Right atrial and ventricular hypertrophy" is based on the clinical scenario given. Hypertension in the elderly can lead to cardiac remodeling, including myocardial hypertrophy (enlargement and thickening of cardiac muscle) due to the prolonged mechanical stress on the heart. In this case, right atrial and ventricular hypertrophy are observed. The ECG findings may include increased amplitude of P wave, QRS complex, and T wave, as well as right axis deviation.

**Why Each Wrong Option is Incorrect:**

A. **Cardiomegaly:** Cardiomegaly refers to an enlarged heart, which is a broader term than hypertrophy. In this scenario, the patient has right atrial and ventricular hypertrophy, which are specific manifestations of mechanical stress due to hypertension.

B. **Atrial flutter:** Atrial flutter is a specific cardiac arrhythmia characterized by regular atrial activity (Wolff-Parkinson-White pattern) and is not directly related to hypertension-induced hypertrophy.

C. **Left ventricular hypertrophy:** Although hypertension can cause left ventricular hypertrophy, the question specifically mentions right atrial and ventricular hypertrophy. This option is incorrect because it includes left ventricular involvement, which is not as relevant in this case.

**Clinical Pearl:**

In an elderly patient with hypertension, the presence of right atrial and ventricular hypertrophy on an ECG can indicate prolonged mechanical stress on the heart. However, it is essential to interpret ECG findings in the context of the clinical scenario provided (hypertension) to make an accurate diagnosis and tailor the appropriate treatment plan.