What initial investigations are recommended for a 21-year-old patient presenting with palpitations, mild chest discomfort, and occasional mild left arm pain, with a normal Electrocardiogram (ECG) and negative cardiac enzymes?

Initial Investigations for a 21-Year-Old with Palpitations

For a 21-year-old patient with palpitations, mild chest discomfort, and occasional mild left arm pain with normal ECG and negative cardiac enzymes, the initial investigations should include a 12-lead ECG, cardiac biomarkers, ambulatory ECG monitoring (Holter or event recorder), and an echocardiogram to rule out structural heart disease. 1

Core Initial Investigations

Immediate Assessment

• 12-lead ECG - even though the initial ECG was normal, comparison with previous ECGs (if available) is valuable, particularly in patients with pre-existing cardiac pathology 1
• Cardiac biomarkers (troponin) - should be repeated after 6-12 hours if initial values are negative 1
• Continuous multi-lead ECG monitoring if the patient is experiencing symptoms during evaluation 1

Secondary Investigations (within 24-72 hours)

• Ambulatory ECG monitoring (Holter monitor for 24-48 hours or event recorder for intermittent symptoms) to capture arrhythmias during symptomatic episodes 1
• Transthoracic echocardiography to assess:
  • Cardiac structure and function
  • Presence of valvular disease (especially mitral valve prolapse)
  • Evidence of hypertrophic cardiomyopathy
  • Wall motion abnormalities 1

Additional Targeted Investigations Based on Initial Findings

If Palpitations Are the Predominant Symptom

• Extended ambulatory monitoring (7-14 days) if 24-48 hour Holter is non-diagnostic 1
• Consider implantable loop recorder if symptoms are infrequent but severe 1

If Structural Heart Disease Is Suspected

• Exercise stress testing, particularly if symptoms are exercise-related 1
• Cardiac MRI if echocardiography is inconclusive or if specific cardiomyopathies (ARVC, HCM) are suspected 1

If Symptoms Suggest Coronary Origin

• Exercise stress testing or pharmacological stress testing with imaging (nuclear perfusion or echocardiography) 1
• Consider coronary CT angiography in patients with intermediate risk factors 1

Special Considerations

For Suspected Arrhythmogenic Cardiomyopathy

• Signal-averaged ECG to detect late potentials 1
• Cardiac MRI with gadolinium enhancement to detect fibrosis or fatty infiltration 1

For Suspected Long QT or WPW Syndrome

• Detailed analysis of the ECG for QT interval, delta waves, and PR interval 2
• Consider genetic testing if family history is positive 1

Pitfalls to Avoid

• Do not dismiss symptoms in young patients with normal initial ECG and biomarkers - subtle cardiac abnormalities may be present despite normal initial testing 3
• Avoid premature discharge without adequate rhythm monitoring if symptoms are recurrent or concerning 1
• Remember that anxiety can cause palpitations, but it should remain a diagnosis of exclusion after cardiac causes have been ruled out 1
• Be aware that stimulant use (including pre-workout supplements, caffeine, energy drinks) can trigger palpitations and should be specifically inquired about 3

By following this systematic approach to investigation, the underlying cause of the patient's symptoms can be identified, allowing for appropriate management and risk stratification.