sinus tachycardia

see also:

• cardiology
• supraventricular tachycardias (SVT)

• a sinus tachycardia is generally defined in adults as being a sinus rhythm with rate greater than 100bpm
• while the patient with sinus tachycardia in the ED may just be anxious, in pain or a result of medications such as the asthmatic patient on beta adrenergic agonists such as salbutamol, a sinus tachycardia may be a sign of an acute pathology and even impending death such as via pulseless electrical activity (PEA), or it may be more subacute as in anaemia, cardiac failure or hyperthyroidism.
• most causes of hypotension will result in a reflex sinus tachycardia via a baroreceptor reflex response (unless this reflex is depressed as well such as in certain drug overdoses or neurologic depression)
• such is the potential importance of this sign, that heart rate is incorporated in the ED “vital observations”, and should not be ignored unless a plausible explanation is possible and more serious causes are reasonably excluded.
• the patient with a steadily rising heart rate in ED over hours suggests ongoing deterioration such as from occult blood loss.
• the heart rate itself is usually NOT treated in the ED (such as with beta adrenergic blockers) unless it is likely to exacerbate an underlying problem - hence Rx to slow the heart rate is mainly reserved for acute myocardial infarction (AMI/STEMI/NSTEMI), aortic dissection and thyrotoxic crisis.
• remember that the normal heart rate varies with age:
  • infants normal heart rate = 110-150 bpm
  • adults normal heart rate = 60-100 bpm although resting HR for most adults is 65-85 bpm
  • exercise results in a normal sinus tachycardia response depending on level of exertion, cardiovascular fitness and age:
    • maximal exercise heart rate is usually given at 200 - age in years

• hypoxia
• hypercapnia - usually a bounding pulse with vasodilation
• hypoglycaemia
• hypovolaemia - eg. dehydration, blood loss (eg. trauma, ectopic pregnancy, upper GIT bleeding, abdominal aortic aneurysm (AAA))
• sepsis / septicaemia
• acute abdominal surgical conditions
• seizures
• acute myocardial infarction (AMI/STEMI/NSTEMI)
• pulmonary embolism (PE)
• aortic dissection
• tension pneumothorax
• cardiac tamponade - eg. trauma, haemopericardium, or a large effusion in pericarditis
  • suggested by electrical alternans and low QRS voltages
  • see https://lifeinthefastlane.com/ecg-library/100-ecgs/quiz-ecg-011/
• drug overdose such as tricyclic antidepressant overdose, amphetamines, anti-muscarinic anticholinergic agents
• drug withdrawal states such as ethanol (alcohol and alcohol withdrawal), opiates, benzodiazepines
• heat illness and heat stroke
• early hypothermia as the body attempts to generate heat by shivering
• metabolic disturbances such as diabetic ketoacidosis (DKA)
• anorexia nervosa / eating disorders

• vasodilators such as nitrates (GTN, etc)
• anti-muscarinic anticholinergic agents
• sympathomimetics such as salbutamol, adrenaline / epinephrine, methylxanthines
• phenothiazines such as iv chlorpromazine

• congestive cardiac failure including Beri Beri (rare in western countries)
• anaemia
• hyperthyroidism
• infective endocarditis (including SBE) - usually CRP is elevated
• fever
• anorexia nervosa / eating disorders

• anxiety
• pain
• caffeine
• smoking - nicotine
• ethanol (alcohol and alcohol withdrawal)
• exertion
• phaechromocytoma
• cardiac deconditioning
• dysautonomia syndromes such as inappropriate sinus tachycardia (ITS) and postural orthostatic tachycardia syndrome (POTS) - usually in young women and often accompanied by chest pains and SOB.