Sinus Tachycardia

Sinus tachycardia is a regular rhythm arising from the sinus node at a rate above 100 beats per minute in adults, with normal P wave morphology preceding every QRS complex. It is a physiological response to a stimulus in most cases and a sign of an underlying problem rather than a primary arrhythmia.

• Physiological: exercise, anxiety, pain, fever, caffeine, nicotine, pregnancy, emotion.
• Pathological: infection or sepsis, anaemia, hypovolaemia or bleeding, hypoxia, pulmonary embolism, heart failure, thyrotoxicosis, phaeochromocytoma, hypoglycaemia, withdrawal states (alcohol, benzodiazepines, opioids), acute coronary syndrome, cardiac tamponade.
• Drugs: salbutamol and other beta agonists, theophylline, thyroxine excess, anticholinergics, decongestants, amphetamines, cocaine, antidepressants, atropine.
• Rate usually does not exceed 220 minus age.

• Palpitations, awareness of heartbeat, breathlessness, anxiety, light headedness, chest tightness.
• Gradual onset and gradual termination (as opposed to abrupt onset in supraventricular tachycardia).
• Symptoms of underlying cause: fever, pallor, weight loss, tremor, heat intolerance, sweating, cough, leg swelling, bleeding, chest pain.
• Examination: regular pulse, check temperature, blood pressure, oxygen saturation, respiratory rate, pallor, goitre, tremor, hydration, heart sounds, calves.
• Red flags: haemodynamic instability, hypoxia, chest pain, syncope, pleuritic pain, haemoptysis, sepsis features, rate persistently above 150 beats per minute at rest.

• 12-lead ECG: regular narrow complex tachycardia with upright P waves in leads I, II and aVF, and inverted P in aVR; rate typically 100 to 150. Distinguish from atrial flutter at 150 (2:1 block) and supraventricular tachycardia.
• Basic tests: full blood count, ferritin, urea and electrolytes, glucose, thyroid stimulating hormone and free thyroxine, C-reactive protein, urine dipstick, pregnancy test.
• Additional tests as guided by history: troponin, D-dimer or CT pulmonary angiogram if embolism is suspected, chest radiograph, blood cultures, echocardiography, 24-hour urine or plasma metanephrines.
• Consider 24 to 48 hour or 7-day ambulatory ECG if persistent unexplained resting tachycardia.
• Differentials: supraventricular tachycardia, atrial flutter, atrial tachycardia, inappropriate sinus tachycardia, postural orthostatic tachycardia syndrome.

Treat the cause (primary management)

• Fever: paracetamol 1 g orally every 4 to 6 hours as needed (maximum 4 g in 24 hours; maximum 3 g in 24 hours if under 50 kg or with liver disease or chronic alcohol use).
• Anaemia: treat iron, B12 or folate deficiency or source of loss.
• Hypovolaemia: oral or intravenous fluids.
• Thyrotoxicosis: carbimazole 15 to 40 mg daily orally, with propranolol 10 to 40 mg orally two or three times daily for symptoms.
• Pain, anxiety, withdrawal: treat specifically.
• Stop or reduce contributing drugs and stimulants.
• Pulmonary embolism, sepsis, acute coronary syndrome, tamponade, severe hypoxia: emergency care.

Symptomatic therapy (only after the cause is addressed or excluded and when symptoms persist)

• Propranolol 10 to 40 mg orally two or three times daily, or bisoprolol 1.25 to 5 mg orally once daily. Contraindicated in asthma, second or third degree heart block, severe bradycardia, decompensated heart failure, and used with caution in diabetes (masked hypoglycaemia).
• Ivabradine 5 mg orally twice daily, adjusted to 2.5 to 7.5 mg twice daily after 2 weeks, is a specialist option when beta blockers are contraindicated. Avoid in pregnancy, severe hepatic impairment, and with strong CYP3A4 inhibitors.

Lifestyle

• Reduce caffeine, energy drinks, nicotine and alcohol; regular sleep; hydration; graded aerobic exercise; relaxation or breathing training for anxiety.

Special groups

• Pregnancy: heart rate normally rises 10 to 20 beats per minute; investigate persistent rates above 120 or associated symptoms; avoid ivabradine.
• Children: normal heart rate is higher and age dependent, so interpret against age norms.
• Older adults: avoid beta blockers if bradycardia or conduction disease is present; seek cause actively.

Follow up and referral

• Review in 2 to 4 weeks after treating the cause.
• Refer if persistent resting rate above 100 with no cause found, abnormal ECG, haemodynamic instability, structural heart disease or if arrhythmia is suspected.