What are the next steps to evaluate a patient with persistent tachycardia, with a resting heart rate in the mid-80s (per minute) and a standing/gentle movement heart rate consistently over 100 (beats per minute)?

Evaluation of Persistent Orthostatic Tachycardia

Obtain a 12-lead ECG immediately to document the rhythm and exclude pre-excitation or other primary arrhythmias, then systematically evaluate for secondary causes including fever, dehydration, anemia, hyperthyroidism, and anxiety before considering inappropriate sinus tachycardia or postural orthostatic tachycardia syndrome (POTS). 1, 2

Initial Diagnostic Workup

Essential First Steps

• 12-lead ECG at rest is mandatory to look for pre-excitation patterns (delta waves suggesting Wolff-Parkinson-White syndrome), prolonged QT interval, or other baseline abnormalities that would require immediate cardiology referral 1, 2

• Assess for hemodynamic stability by checking for chest pain, shortness of breath, hypotension, altered mental status, or signs of heart failure 3, 1

• Obtain vital signs including orthostatic measurements: measure heart rate and blood pressure supine, then after standing for 3,5, and 10 minutes 3, 1

Laboratory Evaluation

• TSH (thyroid function) to exclude hyperthyroidism, which commonly presents with persistent tachycardia 2

• Complete blood count to identify anemia as a reversible cause 1, 2

• Basic metabolic panel to assess for electrolyte abnormalities and dehydration 2

• Consider drug screen if medication-induced tachycardia is suspected 3

Cardiac Imaging and Monitoring

• Echocardiogram to exclude structural heart disease including cardiomyopathy, valvular abnormalities, and assess left ventricular function 1, 2

• 24-hour Holter monitor to document heart rate patterns throughout the day, confirm persistent daytime tachycardia (>100 bpm), mean 24-hour rate, and nocturnal normalization 3, 1

Differential Diagnosis Based on Pattern

Physiologic Sinus Tachycardia (Most Common)

• The upper limit of physiologic sinus tachycardia is approximately 220 minus the patient's age 3, 1

• With rates <150 bpm in the absence of ventricular dysfunction, tachycardia is more likely secondary to an underlying condition rather than the cause of instability 3, 1

• Identify and treat the underlying cause: fever, infection, dehydration, anemia, pain, anxiety, medications, or hyperthyroidism 3, 2

• No specific antiarrhythmic therapy is indicated for physiologic sinus tachycardia; treatment is directed at the underlying cause 3, 2

Inappropriate Sinus Tachycardia

Consider this diagnosis if:

• Persistent resting heart rate >100 bpm with mean 24-hour rate >90 bpm 1
• Excessive heart rate increase with minimal activity 3
• No identifiable physiologic cause after thorough evaluation 3, 1
• Tachycardia is nonparoxysmal (not abrupt onset/termination) 3
• Nocturnal normalization of heart rate on 24-hour monitoring 3

First-line treatment: Beta-blockers should be prescribed as initial therapy 3

Alternative agents: Nondihydropyridine calcium-channel blockers (verapamil or diltiazem) if beta-blockers are ineffective or contraindicated 3

Postural Orthostatic Tachycardia Syndrome (POTS)

• Must be excluded before considering catheter ablation for inappropriate sinus tachycardia 3

• Defined by sustained heart rate increase ≥30 bpm in adults (≥40 bpm in adolescents aged 12-19) within 10 minutes of standing 1

• Requires specialized autonomic testing and cardiology evaluation 3, 4

Supraventricular Tachycardia (SVT)

Critical distinction: SVT has abrupt onset and termination, whereas sinus tachycardia has gradual changes 5, 6

• Diagnosis is frequently delayed due to misdiagnosis as anxiety or panic disorder 2, 5, 6

• Episodes lasting 2 hours are more consistent with paroxysmal SVT (AVNRT or AVRT) than simple anxiety 5

• Requires 12-lead ECG during tachycardia for definitive diagnosis if possible 1

Mandatory Cardiology Referral Criteria

Immediate referral required for: 1, 2, 5

• Pre-excitation (WPW syndrome) on ECG
• Wide-complex tachycardia of unknown origin
• Syncope during tachycardia or with exercise
• Documented sustained SVT
• Recurrent episodes of regular, paroxysmal palpitations with abrupt onset/termination

Critical Pitfalls to Avoid

• Do not normalize heart rate in compensatory tachycardia: When cardiac function is poor, cardiac output can be dependent on a rapid heart rate, and "normalizing" the rate can be detrimental 3, 1

• Do not assume "just anxiety" without proper cardiac evaluation, as SVT and anxiety present with nearly identical symptoms 2, 5, 6

• Do not use AV nodal blocking agents if pre-excitation is present on ECG, as this can be dangerous in atrial fibrillation with WPW 5

• Recognize tachycardia-mediated cardiomyopathy risk: Persistent tachycardia (weeks to months) with fast ventricular response can cause reversible cardiomyopathy requiring careful long-term follow-up 1

Patient Instructions

Seek immediate emergency care if: 5

• Heart rate persistently >150 bpm
• Syncope or near-syncope occurs
• Severe chest pain or shortness of breath develops