**Core Concept**
The patient's presentation suggests a panic attack, which is a sudden onset episode of intense fear or discomfort accompanied by physical symptoms. Panic attacks are a common manifestation of panic disorder, characterized by an abrupt onset of symptoms such as palpitations, sweating, trembling, shortness of breath, and fear of dying or losing control.

**Why the Correct Answer is Right**
The patient's symptoms, including sudden onset breathlessness, anxiety, palpitations, hot flushes, dizziness, and chest pain, are consistent with a panic attack. The absence of physical examination, ECG, and X-ray abnormalities further supports this diagnosis, as panic attacks are typically not associated with underlying cardiac or pulmonary pathology. The patient's fear of dying, although distressing, is a common feature of panic disorder and does not necessarily indicate an underlying cardiac condition.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because the patient's symptoms are not consistent with a cardiac arrhythmia, which would typically be associated with abnormal ECG findings. The normal ECG and X-ray further rule out cardiac-related causes.

**Option B:** This option is incorrect because the patient's symptoms are not consistent with a pulmonary embolism, which would typically be associated with abnormal chest X-ray findings or evidence of right ventricular strain on ECG.

**Option C:** This option is incorrect because the patient's symptoms are not consistent with a hypoglycemic episode, which would typically be associated with symptoms such as tremors, sweating, and hunger, rather than anxiety and palpitations.

**Option D:** This option is incorrect because the patient's symptoms are not consistent with a hyperventilation syndrome, which would typically be associated with respiratory alkalosis and abnormalities on arterial blood gas analysis.

**Clinical Pearl / High-Yield Fact**
The diagnosis of panic disorder can be challenging, as patients often present with symptoms that are similar to those of other medical conditions. However, the presence of a sudden onset episode of intense fear or discomfort, accompanied by physical symptoms, is a key characteristic of panic attacks.

**Correct Answer:** A. Panic attack