What is the initial workup and management for a teenager presenting with sinus tachycardia?

Workup for Sinus Tachycardia in a Teenager

Begin with a 12-lead ECG to confirm sinus origin (positive P waves in leads I, II, aVF; negative in aVR), then immediately assess hemodynamic stability and systematically identify the underlying cause through targeted history, physical examination, and laboratory testing. 1

Immediate Assessment

Determine hemodynamic stability first by evaluating for acute altered mental status, ischemic chest pain, acute heart failure, hypotension, or shock. 1 Check oxygenation immediately with pulse oximetry and look for tachypnea, intercostal retractions, or suprasternal retractions, as hypoxemia is one of the most common reversible causes. 1

Ensure continuous vital sign monitoring and establish IV access if the patient appears unstable. 1

Diagnostic Workup

History and Physical Examination

Focus on identifying physiological triggers:

• Hypovolemia/dehydration: Assess for poor oral intake, vomiting, diarrhea, orthostatic vital signs 2, 1
• Fever/infection: Document temperature, look for infectious sources 2, 1
• Pain or anxiety: Evaluate for acute stressors, emotional distress, or anxiety disorders 2, 1
• Medications and substances: Screen for stimulants (caffeine, energy drinks), prescribed medications (albuterol, aminophylline), recreational drugs (amphetamines, cocaine, cannabis), or anticancer agents 2, 1

Evaluate for serious pathological causes in teenagers:

• Pulmonary embolism: Particularly important in adolescent females on oral contraceptives, presenting with chest pain and syncope 3
• Hyperthyroidism: Look for weight loss, tremor, heat intolerance, goiter 2, 1
• Anemia: Assess for pallor, fatigue, menstrual history in females 2, 1
• Cardiac disease: Inquire about chest pain, dyspnea, exercise intolerance, family history of cardiomyopathy 2

Laboratory Testing

Obtain the following tests systematically:

• Complete blood count: To evaluate for anemia or infection 1
• Thyroid function tests (TSH, free T4): To exclude hyperthyroidism 1
• Urine toxicology screen: If substance use is suspected 4
• Consider D-dimer and CT angiography: If pulmonary embolism is suspected based on risk factors (oral contraceptives, recent immobilization, chest pain, syncope) 3

Electrocardiogram

A 12-lead ECG during tachycardia confirms sinus origin with normal P-wave morphology (positive in leads I, II, aVF; negative in aVR; axis 0-90 degrees). 2, 1 The P waves may have larger amplitude and become peaked during tachycardia. 2

Distinguish sinus tachycardia from other arrhythmias: Sinus tachycardia is non-paroxysmal with gradual onset and termination, unlike AVNRT or AVRT which have abrupt onset/termination. 2 If pre-excitation (delta waves) is present on resting ECG, consider AVRT instead. 2

Additional Testing

24-hour Holter monitoring is indicated if inappropriate sinus tachycardia (IST) is suspected—defined as persistent resting heart rate >100 bpm with mean 24-hour heart rate >90 bpm after excluding secondary causes. 2, 4 IST shows excessive rate increase during activity with nocturnal normalization. 5

Echocardiography is NOT routinely recommended for uncomplicated sinus tachycardia with an identifiable reversible cause. 1 However, obtain an echocardiogram if myocarditis is suspected (gallop rhythm, ECG abnormalities disproportionate to fever) or if structural heart disease is a concern. 2, 1

Electrophysiological studies are NOT routinely recommended but should be considered if concurrent supraventricular tachycardia (AVNRT, AVRT) is suspected based on paroxysmal symptoms with abrupt onset/termination. 2, 4

Critical Pitfalls to Avoid

Never attempt to normalize heart rate in compensatory tachycardia (hypovolemia, hypoxemia, anemia), as cardiac output depends on elevated heart rate and suppressing it can be detrimental. 1

Do not miss pulmonary embolism in adolescent females on oral contraceptives—maintain high clinical suspicion even with nonspecific presentation, as this diagnosis is often underdiagnosed in pediatrics. 3

Always exclude all secondary causes before diagnosing IST, as this is a diagnosis of exclusion. 1, 4 IST predominantly affects young females (90% female, mean age 38 years, but can present in teenagers) and often involves healthcare professionals. 2, 6

Distinguish IST from postural orthostatic tachycardia syndrome (POTS) before initiating rate control, as suppressing sinus rate in POTS causes severe orthostatic hypotension. 1, 7