**Core Concept**
Hypochondriasis, now referred to as Illness Anxiety Disorder (IAD), is a psychiatric disorder characterized by excessive worry about having a serious illness despite medical reassurance and a lack of evidence for the feared condition. This excessive worry leads to significant distress and impairment in daily functioning.

**Why the Correct Answer is Right**
The patient in this scenario exhibits classic symptoms of hypochondriasis, including excessive worry about a perceived health threat, despite medical reassurance and the absence of evidence for the feared illness. This excessive worry is not only a source of distress but also leads to repetitive medical consultations and investigations, which further reinforce the patient's anxiety. The patient's preoccupation with a serious cardiac disorder, despite the doctor's reassurance that it is benign, is a hallmark of hypochondriasis.

**Why Each Wrong Option is Incorrect**
**Option A:** Conversion disorder, now referred to as Functional Neurological Symptom Disorder (FNSD), is characterized by the presence of neurological symptoms that cannot be explained by a medical condition. In this scenario, there is no mention of neurological symptoms, making conversion disorder an unlikely diagnosis.

**Option C:** Somatization is a psychiatric disorder characterized by the presence of multiple, recurring physical complaints that cannot be explained by a medical condition. While the patient in this scenario does have a physical complaint (extra beats in pulse), the primary issue is the excessive worry about having a serious illness, which is more characteristic of hypochondriasis.

**Option D:** Depression is a mood disorder characterized by persistent feelings of sadness, hopelessness, and a loss of interest in activities. While the patient's excessive worry and repetitive medical consultations may be contributing factors to their distress, the primary symptoms described do not align with the diagnostic criteria for depression.

**Clinical Pearl / High-Yield Fact**
A key feature of hypochondriasis is the patient's excessive worry about having a serious illness, despite medical reassurance and a lack of evidence for the feared condition. This excessive worry can lead to significant distress and impairment in daily functioning, making early recognition and intervention crucial.

**✓ Correct Answer: B. Hypochondriosis**