Vasovagal Syncope: This condition is characterized by intermittent episodes of dizziness or fainting, often triggered by stress, pain, or prolonged standing. The presence of heart palpitations during episodes supports this diagnosis, as vasovagal syncope can lead to transient bradycardia or other cardiac rhythm disturbances.

Anxiety-Related Dizziness: Anxiety disorders can cause dizziness, palpitations, and other symptoms without an underlying cardiac issue. The absence of nausea, vomiting, and vision changes makes this a plausible option.
Benign Paroxysmal Positional Vertigo (BPPV): Although BPPV typically presents with vertigo and is triggered by positional changes, some patients may describe their symptoms as dizziness. The lack of nausea and vomiting does not rule out BPPV entirely.
Cardiac Arrhythmias: Conditions like atrial fibrillation or supraventricular tachycardia can cause palpitations and dizziness due to irregular heart rhythms. The patient's admission of heart palpitations during episodes of dizziness makes this a consideration.

Cardiac Ischemia or Myocardial Infarction: Although the patient denies chest pain, atypical presentations of cardiac ischemia can occur, especially in women, diabetics, or the elderly. Dizziness and palpitations could be symptoms of a myocardial infarction.
Aortic Dissection: This is a life-threatening condition that can present with dizziness among other symptoms like severe chest or back pain. The absence of these typical symptoms does not entirely rule out aortic dissection.
Stroke or Transient Ischemic Attack (TIA): While the patient denies vision changes, dizziness can be a symptom of a stroke or TIA, especially if it's a posterior circulation stroke.

Multiple System Atrophy (MSA): A rare neurodegenerative disorder that can cause autonomic dysfunction leading to dizziness and orthostatic hypotension.
Pheochromocytoma: A rare tumor of the adrenal gland that can cause episodic hypertension, palpitations, and dizziness due to excessive catecholamine release.
Chiari Malformation: A structural defect in the cerebellum that can cause dizziness among other neurological symptoms, often worsened by coughing, sneezing, or straining.