What is the appropriate diagnosis and treatment for a patient presenting with severe dizziness, tachycardia, and fainting sensation?

Acute Management of Severe Dizziness with Tachycardia and Near-Syncope

This patient requires immediate cardiovascular assessment for supraventricular tachycardia (SVT) with rate-related symptoms, not primary vestibular workup. The presentation of escalating lightheadedness culminating in near-syncope with documented tachycardia (120-130 bpm) represents hemodynamic compromise requiring urgent rhythm evaluation and stabilization 1.

Immediate Emergency Department Actions

Establish hemodynamic monitoring and obtain a 12-lead ECG immediately to define the rhythm and assess for underlying cardiac pathology 2, 1. The combination of severe lightheadedness (7-8/10), near-syncope, and sustained tachycardia indicates potential rate-related cardiovascular compromise 2.

Critical Initial Steps:

• Attach continuous cardiac monitoring, establish IV access, and measure blood pressure to assess stability 2, 1
• Provide supplementary oxygen if oxygen saturation is inadequate or signs of respiratory distress are present 2, 1
• Obtain 12-lead ECG without delay if the patient remains stable, but do not postpone cardioversion if instability worsens 2, 1
• Evaluate for signs of hemodynamic instability: acute altered mental status, chest discomfort, acute heart failure, hypotension, or shock 2, 1

Differential Diagnosis Priority

Most Likely: Supraventricular Tachycardia (SVT)

The paroxysmal nature of symptoms, heart rate of 120-130 bpm, lightheadedness, and near-syncope strongly suggest SVT, particularly AVNRT or sinus node reentry tachycardia 2. AVNRT typically presents with sudden onset palpitations, dizziness, and rates between 140-250 bpm, predominantly in young women without structural heart disease 2.

• Sinus node reentry tachycardia presents with paroxysmal attacks, lightheadedness, and presyncope, with rates rarely exceeding 180 bpm 2
• Syncope is extremely rare in sinus node reentry tachycardia, making near-syncope consistent with this diagnosis 2

Secondary Consideration: Inappropriate Sinus Tachycardia

If P-wave morphology on ECG is identical to sinus rhythm, inappropriate sinus tachycardia should be considered, particularly given the patient is likely a young healthcare professional or student (attending class) 2. This condition presents with persistent sinus tachycardia, palpitations, dizziness, lightheadedness, and presyncope, predominantly affecting females (90%) with mean age 38 years 2.

Rule Out: Orthostatic Hypotension

Measure orthostatic vital signs to exclude vasovagal syncope or orthostatic hypotension, which account for 22.3% of dizziness presentations 3. However, the sustained tachycardia makes primary orthostatic hypotension less likely.

Treatment Algorithm Based on Stability

If Patient Becomes Unstable:

Perform immediate synchronized cardioversion if signs of rate-related cardiovascular compromise develop (hypotension, altered mental status, chest pain, acute heart failure) 2, 1.

• Sedate the conscious patient immediately before cardioversion if time permits 2, 1
• Use initial biphasic energy of 50-100 J for SVT, increasing stepwise if unsuccessful 2
• Do not delay cardioversion for additional testing if the patient demonstrates hemodynamic instability 2, 1

If Patient Remains Stable (Current Scenario):

For Regular Narrow-Complex Tachycardia (Most Likely):

1. Attempt vagal maneuvers first (Valsalva maneuver for 10-30 seconds, carotid massage for 5-10 seconds after confirming no bruit, or ice-cold wet towel to face) 2
2. Administer adenosine 6 mg rapid IV push, followed by 12 mg if needed, which terminates AVNRT in approximately 95% of cases 2, 1
3. Consider IV beta-blockers (metoprolol 5 mg slow bolus), diltiazem, or verapamil if adenosine is ineffective 2, 1

For Wide-Complex Tachycardia:

If QRS ≥0.12 seconds, presume ventricular tachycardia and prepare for cardioversion while attempting adenosine for diagnosis if the rhythm is regular and monomorphic 2, 1.

Critical Pitfalls to Avoid

• Do not normalize heart rate if it represents compensatory tachycardia for underlying conditions like hypovolemia or anemia, as stroke volume may be limited and cardiac output dependent on rapid rate 2, 1
• Avoid AV nodal blocking agents (adenosine, calcium channel blockers, beta-blockers) if pre-excited atrial fibrillation is suspected on ECG 2, 1
• Do not administer adenosine for irregular or polymorphic wide-complex tachycardia 2, 1
• Do not use multiple AV nodal blocking agents sequentially due to overlapping half-lives causing profound bradycardia 2, 1

Additional Diagnostic Considerations

Evaluate for Secondary Causes:

Identify and treat reversible causes of tachycardia including fever, anemia, hyperthyroidism, dehydration, pulmonary embolism, or medication effects 2, 1.

Assess for Structural Heart Disease:

The unilateral leg pain with temperature changes and tingling warrants evaluation for deep vein thrombosis and pulmonary embolism, which can present with tachycardia, lightheadedness, and near-syncope 2. Consider D-dimer and CT pulmonary angiography if clinical suspicion exists.

Neurologic Symptoms:

The focal headache (6/10 intensity at specific point) requires assessment for intracranial pathology if cardiovascular causes are excluded, though this is less likely given the temporal relationship with tachycardia 2.

Disposition and Follow-Up

If SVT is confirmed and successfully terminated, the patient requires cardiology referral for consideration of electrophysiologic study and possible catheter ablation, particularly if episodes are frequent or poorly tolerated 2.

For inappropriate sinus tachycardia, initiate beta-blocker therapy (metoprolol) as first-line treatment after excluding secondary causes 2. Nondihydropyridine calcium channel blockers (verapamil, diltiazem) are alternative options 2.

Admit patients with concerning ECG findings, structural heart disease, or recurrent symptoms for continuous monitoring and further evaluation 2.