How should I evaluate and manage a patient with normal laboratory studies who has palpitations, a resting heart rate of 90‑110 bpm (tachycardia), intermittent dizziness, loss of balance while walking, and occasional nausea?

Evaluation and Management of Palpitations with Tachycardia and Associated Symptoms

This patient requires immediate 12-lead ECG documentation, systematic exclusion of secondary causes (particularly hyperthyroidism, anemia, and dehydration), and ambulatory monitoring to correlate symptoms with rhythm—with the primary goal of distinguishing benign inappropriate sinus tachycardia from potentially dangerous supraventricular or ventricular arrhythmias. 1, 2

Immediate Diagnostic Steps

Obtain 12-Lead ECG Now

• Document the rhythm during symptoms if possible to determine if tachycardia is regular or irregular, narrow or wide complex 1, 2
• Look specifically for pre-excitation (delta waves suggesting Wolff-Parkinson-White syndrome), QT prolongation, or evidence of structural heart disease 2, 3
• Assess P-wave morphology: upright in leads I, II, and aVF with biphasic appearance in V1 suggests sinus origin 1
• Do not rely on automated ECG interpretation—these systems are notoriously unreliable 2

Critical Pattern Recognition

The combination of resting heart rate 90-110 bpm with dizziness, balance problems, and nausea suggests several possibilities that require different management:

Regular rhythm patterns: 1, 2

• Inappropriate sinus tachycardia (IST): Gradual onset/termination, persistent elevation at rest (>100 bpm) and 24-hour average >90 bpm without physiologic cause 1
• Paroxysmal SVT (AVNRT/AVRT): Sudden onset and termination, often responds to vagal maneuvers 1, 2
• Atrial flutter with regular conduction: Typically faster rates but can present in this range 1

Irregular rhythm patterns: 2

• Atrial fibrillation: Irregularly irregular rhythm
• Frequent PACs or PVCs: Described as "skipped beats" 3

Exclude Secondary Causes First (Class I Recommendation)

Before diagnosing primary arrhythmia, systematically rule out: 1

Mandatory Laboratory Testing

• Thyroid-stimulating hormone (TSH): Hyperthyroidism causes 5-15% of atrial fibrillation cases and commonly presents with sinus tachycardia 2
• Complete blood count: Exclude anemia as a cause of compensatory tachycardia 1
• Basic metabolic panel: Assess for electrolyte abnormalities (potassium, magnesium, calcium) and renal function 1, 3
• Fasting glucose: Screen for diabetes and hypoglycemia 1

Medication and Substance Review

• Stop all caffeine, alcohol, and nicotine immediately 2
• Review for beta-agonists (albuterol, salmeterol), stimulants, over-the-counter supplements, and illicit drugs (amphetamines, cocaine) 1, 3
• Check for QT-prolonging medications that increase arrhythmia risk 3

Assess for Dehydration and Infection

• Volume status examination and vital signs for fever 1
• Pain assessment (pain can trigger physiologic sinus tachycardia) 1

Ambulatory Monitoring Strategy

The choice of monitoring depends on symptom frequency: 2

For Daily Palpitations

• 24-48 hour Holter monitoring is appropriate when symptoms occur daily 2
• This will capture heart rate patterns, rhythm during symptoms, and average 24-hour heart rate (>90 bpm average supports IST diagnosis) 1

For Less Frequent Symptoms (Several Times Per Week)

• Event recorder or loop recorder has superior diagnostic yield and is more cost-effective than Holter monitoring 2
• Patient activates device during symptomatic episodes
• Monitoring must continue until symptoms occur while wearing the device—non-diagnostic monitoring is not conclusive 2

For Rare but Severe Symptoms (<2 Episodes Per Month)

• Consider implantable loop recorder if symptoms are associated with syncope, presyncope, or severe hemodynamic compromise 2

Teach Vagal Maneuvers Immediately

Instruct the patient in Valsalva maneuver and carotid massage to perform during episodes: 2

• If tachycardia terminates with vagal maneuvers, this confirms re-entrant tachycardia involving AV nodal tissue (AVNRT or AVRT) 1, 2
• Document response during symptomatic episodes to aid diagnosis 2

Echocardiography Indications

Order transthoracic echocardiogram if: 1, 2

• Sustained SVT is documented on monitoring
• Clinical suspicion of structural heart disease (murmur on exam, symptoms of heart failure)
• To exclude cardiomyopathy, valvular disease (including mitral valve prolapse), or congenital abnormalities 1, 3

Note: Physical examination alone cannot reliably exclude structural heart disease 2

Empiric Medical Therapy While Awaiting Monitoring

Beta-blocker may be prescribed empirically after excluding significant bradycardia (<50 bpm on ECG): 1, 2

• Preferred for symptom control in both IST and SVT
• Use with caution and monitor for hypotension (common side effect in IST) 1

Critical warning: 1, 2

• Never start Class I or III antiarrhythmic drugs without documented arrhythmia due to significant proarrhythmic risk
• Do not start multiple rate-control agents simultaneously

Red Flags Requiring Immediate Specialist Referral

Refer urgently to cardiac electrophysiology if: 2

Absolute Indications

• Pre-excitation (delta waves) on ECG with any history of palpitations—risk of sudden death with atrial fibrillation and accessory pathway 2
• Wide complex tachycardia documented on any rhythm strip—may represent ventricular tachycardia 2, 3
• Syncope or near-syncope during palpitations—suggests hemodynamically significant arrhythmia 2, 3

Strong Relative Indications

• Severe dyspnea or chest pain during episodes 2
• Family history of sudden cardiac death in first-degree relatives 3
• Drug resistance or intolerance after trial of beta-blocker 1
• Patient preference to avoid lifelong medication 1

Management Based on Final Diagnosis

If Inappropriate Sinus Tachycardia (IST) is Confirmed

IST diagnosis requires: 1

• Resting heart rate >100 bpm
• Average 24-hour heart rate >90 bpm
• Exclusion of all secondary causes
• Associated symptoms (weakness, fatigue, lightheadedness, uncomfortable heart racing)

Treatment approach (prognosis is benign, treatment is for symptom reduction): 1

1. Ivabradine is reasonable for ongoing management (Class IIa recommendation) 1

   • Selectively lowers heart rate without hemodynamic effects
   • FDA-approved for heart failure, used off-label for IST

2. Beta blockers may be considered (Class IIb recommendation) 1

   • Often ineffective or poorly tolerated due to hypotension
   • Combination with ivabradine may be considered 1

3. Exercise training may provide benefit though unproven 1

4. Recognize that lowering heart rate may not alleviate all symptoms 1

If Paroxysmal SVT (AVNRT/AVRT) is Documented

Refer to cardiac electrophysiology for catheter ablation consideration: 2

• Catheter ablation has high success rate with <5% recurrence and <1% risk of heart block 2
• Potentially curative, avoiding lifelong medication 2
• Young patients with normal structural hearts are ideal candidates 2

If Atrial Fibrillation is Documented

Assess stroke risk using CHA₂DS₂-VASc score and initiate anticoagulation if indicated 1, 2

• Rate control with beta-blocker, diltiazem, or verapamil (target resting heart rate <110 bpm with lenient control strategy) 1
• Consider rhythm control strategy if symptomatic despite rate control 1

Special Considerations for This Patient's Symptoms

Dizziness and Balance Problems

• May indicate hemodynamic compromise during tachycardia episodes 1, 3
• Orthostatic vital signs should be checked to exclude postural orthostatic tachycardia syndrome (POTS), which overlaps with IST but requires different management 1
• Do not aggressively suppress heart rate in POTS as this can cause severe orthostatic hypotension 1

Nausea

• Can be associated with SVT, particularly AVNRT due to elevated atrial pressures 1
• Polyuria occurs in approximately 15% of SVT patients due to elevated atrial natriuretic peptide 1, 2

Common Pitfalls to Avoid

• Do not order comprehensive laboratory panels routinely—focus on TSH, CBC, and basic metabolic panel 2
• Do not dismiss syncope with palpitations as benign—this requires urgent evaluation 2, 3
• Do not use automatic ECG interpretation without manual verification 2
• Do not start antiarrhythmic drugs empirically without rhythm documentation 1, 2
• Do not assume normal blood work excludes cardiac causes—structural and electrical heart disease can exist with normal labs 4

Follow-Up Plan

Structured follow-up should assess: 1

• Has the risk profile changed (new hypertension, diabetes)?
• Have symptoms improved on therapy?
• Are there signs of proarrhythmia (QT prolongation, new pauses)?
• Has paroxysmal arrhythmia progressed to persistent form?
• Is rate control adequate (target <110 bpm at rest)?

Repeat 12-lead ECG at each visit to document rhythm and assess for interval changes 1