What lab work is recommended for patients presenting with palpitations?

Recommended Laboratory Tests for Patients Presenting with Palpitations

For patients presenting with palpitations, the recommended initial laboratory workup includes complete blood count, serum electrolytes (including calcium and magnesium), thyroid-stimulating hormone, and a 12-lead ECG. 1

Core Laboratory Tests

• Complete blood count (CBC) to assess for anemia, which can precipitate palpitations 1
• Serum electrolytes including sodium, potassium, calcium, and magnesium to identify electrolyte disturbances that can trigger arrhythmias 1
• Thyroid-stimulating hormone (TSH) to rule out hyperthyroidism as a cause of palpitations 1
• Fasting blood glucose or glycohemoglobin (HbA1c) to identify hypoglycemia or diabetes as potential contributors 1
• 12-lead electrocardiogram (ECG) to identify any underlying arrhythmias or structural abnormalities 2, 1

Additional Testing Based on Clinical Presentation

• Brain natriuretic peptide (BNP) and high-sensitivity troponin may be considered if cardiac cause is suspected, though their usefulness is uncertain 2
• Targeted blood tests should be ordered based on clinical assessment from history, physical examination, and ECG findings rather than routine comprehensive laboratory testing 2
• Routine and comprehensive laboratory testing has been shown to be not useful in the evaluation of patients with syncope or palpitations 2

Cardiac Monitoring and Imaging

• 48-hour ambulatory ECG monitoring is recommended for patients with frequent or sustained palpitations 2, 3
• For patients with less frequent episodes, an event recorder or implantable loop recorder may be more appropriate 2, 3
• Transthoracic echocardiography should be performed in selected patients when structural heart disease is suspected 2, 1
• Exercise stress testing can be useful for patients who experience palpitations during or after exertion 2, 1

Special Considerations

• The choice of cardiac monitor should be determined based on the frequency and nature of syncope events 2
• For patients with frequent palpitations, a Holter monitor is appropriate 2
• For infrequent episodes, external loop recorders, patch recorders, or mobile cardiac outpatient telemetry may be more useful 2
• An implantable cardiac monitor can be useful for selected ambulatory patients with syncope or palpitations of suspected arrhythmic etiology 2

Common Pitfalls to Avoid

• Assuming palpitations are benign without appropriate workup, especially in patients with risk factors for cardiac disease 3
• Ordering excessive laboratory tests that are unlikely to yield diagnostic information 2
• Failing to correlate symptoms with cardiac rhythm through appropriate monitoring 3
• Not considering non-cardiac causes such as anxiety, caffeine, or medication effects 1
• Overlooking the need for cardiac monitoring in patients with infrequent but concerning episodes 2

Remember that while most palpitations are benign, they can sometimes indicate serious underlying cardiac conditions that require prompt diagnosis and treatment. The diagnostic approach should be guided by the clinical presentation, with the goal of identifying or excluding potentially serious causes.