What is the cause of constant dizziness in an adult patient with a history of aortic valve replacement, normal MRI brain result, and no valve regurgitation or stenosis?

Evaluation of Constant Dizziness After Aortic Valve Replacement

In a patient with constant dizziness following aortic valve replacement with a well-functioning prosthetic valve and normal brain MRI, the most likely causes are peripheral vestibular disorders (35-55% of dizziness cases), medication side effects, or psychiatric conditions (10-25% of cases), rather than cardiac or neurologic pathology. 1, 2

Systematic Diagnostic Approach

Characterize the Dizziness Pattern

The key to diagnosis is identifying timing and triggers rather than attempting to classify the quality of dizziness, as patients describe symptoms inconsistently 3:

• Episodic vertigo triggered by head motion suggests benign paroxysmal positional vertigo (BPPV) 3
• Episodic vertigo with unilateral hearing loss indicates Ménière's disease 3
• Constant disequilibrium points toward medication effects, neuropathy, or Parkinson disease 1
• Presyncope (near-fainting) suggests orthostatic hypotension or medication side effects 1

Essential Physical Examination Maneuvers

Perform these specific bedside tests to narrow the differential 3:

• Orthostatic vital signs (measure blood pressure supine and after 3 minutes standing) to detect medication-induced hypotension—critical in patients on anticoagulation or antihypertensives after valve replacement 1, 3
• Dix-Hallpike maneuver to diagnose BPPV, the most common peripheral vestibular cause 1, 3
• Assessment for nystagmus to distinguish peripheral (horizontal, fatigable) from central (vertical, non-fatigable) causes 3
• HINTS examination (head-impulse, nystagmus, test of skew) if acute vestibular syndrome is suspected 3

Medication Review is Critical

Systematically review all medications, as this is the most common reversible cause of presyncope and disequilibrium in cardiac patients 1:

• Anticoagulants (warfarin, DOACs) required for mechanical valves
• Beta-blockers and other antihypertensives
• Diuretics causing volume depletion
• Any recently initiated medications

When Laboratory Testing is Indicated

Routine laboratory tests and imaging have low diagnostic yield in patients with normal brain MRI and should only be ordered based on specific clinical findings 2:

• Complete blood count if anemia suspected
• Metabolic panel if on diuretics or concern for electrolyte abnormalities
• Thyroid function if symptoms suggest thyroid dysfunction
• Do not order routine EEG, additional brain imaging, or vestibular function tests without specific clinical indication 2, 4

Cardiac Considerations in This Population

Verify Hemodynamic Status

Although the valve is reportedly well-seated without stenosis or regurgitation, confirm 5:

• Left ventricular ejection fraction and stroke volume index (low flow <35 mL/m² can cause symptoms even with normal EF) 5
• Presence of atrial fibrillation, which causes clinical deterioration in valve patients and may present as dizziness 5
• Adequacy of cardiac output during activity

Rule Out Prosthetic Valve Complications

Despite normal initial assessment, consider 6:

• Prosthetic valve endocarditis (vegetations ≥1 cm detectable on CT)
• Paravalvular leak causing hemodynamic compromise
• Thrombus formation on mechanical valves

Most Likely Diagnoses and Management

Benign Paroxysmal Positional Vertigo (BPPV)

If Dix-Hallpike positive, treat with Epley maneuver (canalith repositioning procedure) 1, 3

Medication-Induced Orthostatic Hypotension

If orthostatic vital signs positive, reduce or adjust antihypertensive medications, increase salt/fluid intake, or consider alpha agonists or mineralocorticoids 1

Vestibular Neuritis

If constant vertigo without hearing loss, treat with vestibular suppressants acutely and vestibular rehabilitation therapy 3

Psychiatric Causes

If no peripheral or central findings, screen for depression, anxiety, and hyperventilation syndrome, which account for 10-25% of dizziness cases 1, 2

Critical Pitfalls to Avoid

• Do not assume cardiac etiology simply because of valve replacement history when valve function is normal 2
• Do not order extensive cardiovascular or neurologic testing without specific clinical indication, as yield is extremely low 2
• Do not overlook medication side effects, the most common reversible cause in this population 1
• Recognize that 10-20% of dizziness cases remain undiagnosed despite thorough evaluation, and most are self-limited with benign prognosis 2

The history and physical examination will identify the probable cause in approximately 75% of patients, making targeted bedside assessment far more valuable than laboratory or imaging studies 2.