**Core Concept**
Brugada syndrome is a genetic disorder characterized by abnormal electrical activity in the heart, leading to a risk of sudden cardiac death. It is diagnosed based on a combination of clinical presentation, family history, and specific electrocardiographic (ECG) and genetic findings.

**Why the Correct Answer is Right**
To diagnose Brugada syndrome, besides ECG, genetic testing is required to identify mutations in the SCN5A gene, which is responsible for the disease. The genetic test helps confirm the diagnosis in individuals with a characteristic ECG pattern, known as a Brugada pattern, and a family history of sudden cardiac death. Genetic testing also helps identify carriers and at-risk family members. In some cases, imaging studies like echocardiography or cardiac MRI may be performed to rule out other cardiac abnormalities.

**Why Each Wrong Option is Incorrect**
* **Option A:** Holter monitoring is not required to diagnose Brugada syndrome, as it is not a dynamic condition that requires continuous monitoring.
* **Option B:** Chest X-ray is not a diagnostic tool for Brugada syndrome, as it does not provide information on cardiac electrical activity or genetic mutations.
* **Option C:** Troponin levels are not relevant to the diagnosis of Brugada syndrome, as they are used to diagnose acute myocardial infarction, not cardiac electrical disorders.

**Clinical Pearl / High-Yield Fact**
Remember that Brugada syndrome is a genetic disorder, and genetic testing is essential to confirm the diagnosis. A family history of sudden cardiac death and a characteristic ECG pattern are also crucial diagnostic clues.

**Correct Answer: D. Genetic testing**