**Core Concept:**
The question is testing our understanding of various symptoms and signs that can be present in a patient with a cardiovascular disorder, particularly focusing on a condition known as panic disorder or panic attack. Panic disorder is a type of anxiety disorder characterized by repeated, unexpected panic attacks, which are acute episodes of intense fear characterized by specific symptoms.

**Why the Correct Answer is Right:**
In this case, the patient presents with sudden onset breathlessness, anxiety, palpitations, and feeling of impending doom, which are all classic symptoms of a panic attack. Panic attacks are typically caused by a malfunction in the body's normal response to stress, known as the autonomic nervous system (ANS) response. When a person experiences a panic attack, the ANS triggers a cascade of physiological changes, such as tachycardia, hyperventilation, and increased blood pressure, which can lead to the symptoms described in the question.

**Why Each Wrong Option is Incorrect:**
A. This option is incorrect because the described symptoms are not typically associated with asthma or any respiratory issue.
B. While heart-related symptoms can be present in a panic attack, the sudden onset and absence of any significant physical examination findings make this option less likely.
C. This option is incorrect because the sudden onset, specific symptoms, and normal examination findings rule out most cardiac causes of breathlessness and anxiety.
D. This option is incorrect because the sudden onset and normal examination findings make it less likely.

**Clinical Pearl:**
Panic disorder and panic attacks can be challenging to diagnose due to their sudden onset and nonspecific symptoms. However, their key features (such as breathlessness and anxiety) should prompt a thorough evaluation for an underlying psychiatric disorder. In such cases, a combination of clinical history, physical examination, and further investigations can help confirm the diagnosis.

**Correct Answer:**
The correct answer is D. Panic disorder and panic attacks can present with specific symptoms such as breathlessness and anxiety, but the sudden onset and normal examination findings make cardiac causes less likely. A thorough clinical history and psychiatric evaluation are essential to diagnose panic disorder accurately.