Sinus Tachycardia

Overview

• Sinus tachycardia is defined as increased sinus heart rate of > 100 beats/minute and is most common rhythm disturbance.
• General evaluation for diagnosing sinus tachycardia:
  • history and physical exam (orthostatic vitals can help distinguish orthostatic hypotension and postural orthostatic tachycardia syndrome [POTS] from inappropriate sinus tachycardia [IST])
  • electrocardiography
    • to confirm presence of sinus tachycardia and exclude other atrial tachyarrhythmias
    • to determine frequency of tachycardia
      • persistent tachycardia suggests normal sinus tachycardia (NST) or IST
      • paroxysmal tachycardia suggests POTS
  • evaluate for causes of NST, including physiologic, pathologic, and drug causes
  • if physiologic, pathologic, and drug causes of sinus tachycardia excluded
    • determine if symptom trigger present
      • symptoms triggered by orthostatic stress suggest POTS
      • symptoms triggered by emotional or psychological stress suggest IST
    • if sinus tachycardia paroxysmal and no obvious trigger, consider evaluation for sinus node reentrant tachycardia (SNRT) (sudden bursts of sinus tachycardia triggered and/or terminated by premature atrial beats suggests sinus node reentrant tachycardia)
  • IST is diagnosis of exclusion and requires presence of distressing symptoms.
  • If POTS suspected, consider tilt testing in select patients (HRS Class IIb, Level E), such as in patients with clinical features of POTS but normal orthostatic vitals.
• Management
  • NST typically resolves with correction of underlying cause.
  • For IST:
    • treatment intended for symptom reduction and treatment of tachycardia alone may not improve symptoms
    • close follow-up with attention and communication about patient symptoms reported to improve outcomes
    • lifestyle modifications (such as exercise training and elimination of stimulants that can cause sinus tachycardia) may be helpful
    • ivabradine can be useful for treating IST (HRS Class I, Level E; ACC/AHA/HRS Class IIa, Level B-R) at dose 5-7.5 mg twice daily
    • sinus node modification, surgical ablation, and sympathetic denervation are not recommended as part of routine care for IST (HRS Class III, Level E)
  • For management of POTS, see POTS
  • For SNRT:
    • no specific medication recommended, but symptomatic patients may respond to adenosine, amiodarone, beta-blockers, nondihydropyridine calcium-channel blockers, or digoxin
    • see also Supraventricular tachycardia (SVT) for management of focal atrial tachycardia (SNRT is an uncommon type of focal atrial tachycardia)

General Information

Description

• Sinus tachycardia is defined as increased sinus heart rate of > 100 beats/minute.

Types

• Normal sinus tachycardia (NST, also called physiologic or appropriate sinus tachycardia) refers to appropriate increase in sinus heart rate of > 100 beats/minute in response to physiologic, pathologic, or pharmacologic stimuli.
• Primary sinus tachycardias refer to increase in sinus heart rate of > 100 beats/minute that is not appropriate for degree of physiologic, pharmacologic, or pathologic stress and include:
  • Inappropriate sinus tachycardia (IST)
    • persistent increase in resting heart rate to > 100 beats/minute
    • mean 24-hour heart rate > 90 beats/minute
    • heart rate usually normalizes at night
    • requires presence of distressing symptoms of palpitations and exclusion of primary cause
  • Postural orthostatic tachycardia syndrome (POTS)
    • abnormal sinus tachycardia triggered by orthostatic stress and relieved by recumbency
    • requires absence of orthostatic hypotension during upright posture and absence of underlying cause or signs of autonomic neuropathy
  • Sinus node reentry tachycardia (SNRT)
    • sudden, paroxysmal, and usually nonsustained sinus tachycardia
    • heart rate usually 100-150 beats/minute, but may be as low as 80 beats/minute
    • usually triggered and terminated by premature atrial beat

Epidemiology

• Sinus tachycardia is most common rhythm disturbance.
• Normal sinus tachycardia is most common type of sinus tachycardia and more commonly affects women than men.
• Postural orthostatic tachycardia (POTS) has 2% reported prevalence and more commonly affects women than men.
• Sinus node reentrant tachycardia reported to account for < 5% of all regular supraventricular tachycardia.

Etiology and Pathogenesis

Causes of Normal Sinus Tachycardia

• Physiologic causes
  • anxiety
  • emotion
  • physical exertion
  • panic attack
  • pain
  • exercise
  • minimal exertion if deconditioning or sedentary lifestyle
• Pathologic causes
  • Cardiac
    • heart failure
    • myocardial infarction
    • aortic regurgitation
    • mitral regurgitation (J Am Coll Cardiol 2013 Feb 26;61(8):793)
    • pericarditis (J Am Coll Cardiol 2013 Feb 26;61(8):793)
  • Pulmonary
    • pulmonary embolism (PE)
    • pneumothorax
    • asthma
    • pneumonia
    • pulmonary edema
  • Endocrine abnormalities
    • thyrotoxicosis
    • hyperthyroidism
    • hypoglycemia
  • Other
    • chronic anemia
    • hypovolemia
    • infection with fever
    • malignancy
    • shock, including sepsis
    • dehydration
• Medications
  • epinephrine
  • norepinephrine
  • dopamine
  • dobutamine
  • salbutamol
  • atropine
  • methylxanthines
  • chemotherapeutic agents, such as doxorubicin and daunorubicin
  • albuterol (J Am Coll Cardiol 2016 Apr 5;67(13):e27)
• Beta-blocker withdrawal
• Ablation of supraventricular tachycardia, including ablation of atrioventricular nodal reentrant tachycardia.
• Recreational and illicit substances
  • smoking (nicotine, tobacco)
  • amphetamines
  • ecstasy
  • cannabis
  • cocaine
  • lysergic acid (LSD)
  • psilocybin (magic mushrooms)
• Dietary exposures
  • caffeine (coffee, tea, and cola)
  • chocolate
  • alcohol

Pathogenesis

• Normal sinus node and heart rate regulation in healthy persons
  • sinus node rate predominantly regulated by calcium clock (L-type calcium channel) and funny current (I_f current) in dynamic process involving cell-to-cell communication and electrical isolation from atrial muscle
  • sinus activation and heart rate also modulated by autonomic nervous system
    • sympathetic (beta-a) stimulatory receptors and muscarinic (M2) inhibitory receptors are modulated by sympathetic and parasympathetic autonomic neuron activity that may be local (ganglionated plexi) or central (if central, modulation also occurs by baroreflexes and other neurohumoral influences)
    • at rest, sinus node regulated mostly by tonic and phasic parasympathetic activation
    • with exercise, sinus rates elevate due to release of vagal activation, sympathetic activation, and increase in catecholamine levels
• In inappropriate sinus tachycardia, any normal process regulating sinus rate may be disrupted, but proposed pathologic mechanisms include
  • intrinsic sinus node abnormality (such as overactivity of L-type calcium channel or funny current)
  • autonomic influence
    • decreased parasympathetic activity
      • M2 receptor autoantibody
      • M2 receptor hyposensitivity
      • lack of appropriate inhibitory effects of vagus nerve on sinus node
    • overactivity of sympathetic nervous system
      • beta receptor stimulating autoantibody
      • beta adrenergic receptor supersensitivity
    • combined parasympathetic and sympathetic activity (baroreceptor activity)
      • impaired baroreflex control
      • reduction in and alteration of baroreflex gain
    • central autonomic stimulation/overactivity
    • blunted response of adenosine with or without autonomic blockade
    • impaired or depressed efferent parasympathetic function despite preservation of sympathovagal balance
    • nociceptive stimulation
  • aberrant neurohormonal modulation due to
    • vasoactive intestinal polypeptide
    • histamine
    • norepinephrine
    • epinephrine
    • serotonin 1-A receptor activation
    • central gamma-aminobutyric acid (BAGA)-nergic activation
    • substance P
    • Reference - J Am Coll Cardiol 2013 Feb 26;61(8):793
  • overactivity of L-type calcium channel or funny current
  • inappropriate sinus tachycardia reported as late complication of mediastinal radiotherapy in case report (Ann Cardiol Angeiol (Paris) 1995 Apr;44(4):185)
  • inappropriate sinus tachycardia reported in completely denervated heart after bicaval orthotopic cardiac transplantation and proposed to be due to primary defect in donor sinus node in 53-year-old man in case report (resting heart rate typically elevated in cardiac transplant recipients due to central autonomic denervation, but sinus rates usually < 110 beats/minute) (Heart Rhythm 2011 May;8(5):781)
• Familial inappropriate sinus tachycardia proposed to involve R524Q gain of function mutation in hyperpolarization-activated cyclic nucleotide-gated (HCN) channel (molecular component of funny channel) that leads to increased sensitivity to second messenger cyclic adenosine monophosphate (cAMP) (key mediator in sympathetic modulation) (J Interv Card Electrophysiol 2016 Jun;46(1):19)
• Etiology and pathophysiology of postural orthostatic tachycardia syndrome (POTS) remain unknown but are likely associated with several heterogeneous, overlapping pathophysiological processes (Clin Auton Res 2011 Apr;21(2):69)

General Evaluation

Testing Strategy

• Use electrocardiography (ECG) to confirm sinus tachycardia present and exclude other atrial tachyarrhythmias
• Determine frequency of tachycardia
  • persistent tachycardia suggests normal sinus tachycardia (NST) or inappropriate sinus tachycardia (IST)
  • paroxysmal tachycardia suggests postural orthostatic tachycardia syndrome (POTS) or sinus node reentrant tachycardia (SNRT)
• Evaluate for causes of NST, including physiologic, pathologic, and drug causes
• If physiologic, pathologic, and drug causes of sinus tachycardia excluded
  • determine if symptom trigger present
    • symptoms triggered by orthostatic stress suggest POTS
    • symptoms triggered by emotional or psychological stress suggest IST
    • Reference - J Am Coll Cardiol 2013 Feb 26;61(8):793
  • if sinus tachycardia paroxysmal and no obvious trigger, consider evaluation for sinus node reentrant tachycardia (sudden bursts of sinus tachycardia triggered and/or terminated by premature atrial beats suggests sinus node reentrant tachycardia)
• IST is diagnosis of exclusion and requires presence of distressing symptoms
• If POTS suspected, consider tilt testing in select patients (HRS Class IIb, Level E), such as in patients with clinical features of POTS but normal orthostatic vitals
• If SNRT suspected, 24-hour or 48-hour Holter monitor might show short sudden bursts of sinus tachycardia triggered or terminated by premature atrial beats

Differential Diagnosis

• atrial tachycardias originating close to sinus node
• right upper pulmonary vein tachycardia
• atrial flutter
• atrioventricular reentry tachycardia (AVRT)

History

Chief Concern (CC)

• If present, symptoms may include
  • palpitations (fast and regular)
  • dyspnea
  • lightheadedness
  • presyncope
• Inappropriate sinus tachycardia usually associated with multiple distressing symptoms, including:
  • palpitations
  • dyspnea
  • lightheadedness
  • weakness
  • chest discomfort
  • syncope (rare)
  • other possible complaints
    • fatigue
    • dizziness
    • presyncope
    • Reference - J Am Coll Cardiol 2013 Feb 26;61(8):793
• Postural orthostatic tachycardia syndrome (POTS)
  • symptoms associated with orthostatic intolerance
    • cardiac symptoms may include:
      • rapid palpitations
      • lightheadedness
      • chest discomfort
      • dyspnea
      • exercise intolerance
      • presyncope
      • syncope
    • noncardiac symptoms may include:
      • mental clouding
      • headache (including migraine)
      • tremor
      • nausea
      • generalized weakness
      • blurred or tunnel vision
  • nonspecific symptoms that are not associated with orthostatic intolerance may include:
    • nausea
    • abdominal pain
    • bloating
    • diarrhea
    • bladder symptoms
    • abnormal sudomotor regulation
    • hypermobile joints
    • exercise intolerance
    • migraine headaches
    • sleep disturbances
    • fatigue
    • acral coldness or pain
  • Reference - Curr Neurol Neurosci Rep 2015 Sep;15(9):60

History of Present Illness (HPI)

• Ask about symptom triggers
  • symptoms triggered by orthostatic stress and relieved by recumbency may suggest postural orthostatic tachycardia syndrome (POTS)
  • symptoms triggered by emotional or physiologic stress may suggest inappropriate sinus tachycardia (IST)
  • symptoms triggered by recent viral infection or exposure to toxin (such as hydrocarbons), may suggest IST
• Ask about frequency of sinus tachycardia
  • persistent tachycardia may suggest normal sinus tachycardia or IST
  • paroxysmal tachycardia may suggest POTS or sinus node reentry tachycardia (SNRT)
• Ask about onset of tachycardia episode
  • gradual onset of persistent tachycardia may suggest IST
  • abrupt onset of paroxysmal tachycardia may suggest supraventricular tachycardia
• presence of autonomically mediated symptoms (such as tremor and constipation) may suggest POTS

Medication History

• Ask about medications that cause sinus tachycardia, such as epinephrine, norepinephrine, and dopamine

Social History

• Ask about use of recreational and illicit substances that cause sinus tachycardia, such as amphetamines, ecstasy, cocaine, and cannabis
• Ask about dietary exposures that may cause sinus tachycardia, such as chocolate, coffee, tea, cola, and alcohol

Past Medical History (PMH)

• Psychiatric disorders (such as panic disorder, depression, schizophrenia, and somatic symptom disorder) often coexist in patients with inappropriate sinus tachycardia (J Am Coll Cardiol 2013 Feb 26;61(8):793)
• Ask about history of therapies that have been reported to cause inappropriate sinus tachycardia, such as
  • cardiac transplantation
  • mediastinal radiotherapy

Physical

• Orthostatic vitals can help distinguish orthostatic hypotension and postural orthostatic tachycardia syndrome (POTS) from inappropriate sinus tachycardia (IST)³
• For patients with suspected IST
  • perform complete physical (HRS Class I, Level E)
  • evaluation for reversible causes recommended (ACC/AHA/HRS Class I, Level C-LD) with careful history and physical and lab tests and imaging studies as necessary (J Am Coll Cardiol 2016 Apr 5;67(13):e27)
• For patients with suspected POTS
  • perform physical exam with orthostatic vitals (HRS Class I, Level E)
  • criteria for POTS diagnosis includes increase in heart rate ≥ 30 beats/minute with upright posture from supine position (increase in heart rate > 40 beats/minute required for patients < 20 years old) in absence of orthostatic hypotension
  • standing heart rate is often ≥ 120 beats/minute and is typically higher in morning than evening
• For patients with suspected sinus node reentrant tachycardia (SNRT), arrhythmia unlikely to be present during physical exam, but look for signs of heart disease
• Determining type of sinus tachycardia based on heart rate can be challenging
  • heart rate may sometimes be persistently raised in patients with POTS
  • heart rate may fluctuate during orthostatic vital measurement in patients with IST

Electrocardiography (ECG)

• 12-lead ECG can confirm sinus tachycardia
• Perform 12-lead ECG in patients being assessed for
  • inappropriate sinus tachycardia (IST) (HRS Class I, Level E)
  • postural orthostatic tachycardia syndrome (POTS) (HRS Class I, Level E)
• 12-lead ECG can identify cardiac cause of tachycardia
• 12-lead ECG can be useful for determining sinus rhythm to differentiate sinus tachycardia from other atrial tachyarrhythmias, such as atrial flutter and atrial tachycardias
• Tachycardia patterns based on type of sinus tachycardia
  
  • persistent increase in resting heart rate to > 100 beats/minute that normalizes at night suggests IST
  • paroxysmal, regular, self-terminating sinus tachycardia suggests sinus node reentry tachycardia (SNRT)

Table 1. ECG Features of Sinus Tachycardia and Other Atrial Arrhythmias

ECG Features of Sinus Tachycardia	ECG Features of Other Atrial Tachyarrhythmias	ECG Features of Right Upper Pulmonary Vein Tachycardia and Atrial Tachycardia Originating from Crista Terminalis or Sinoatrial Node
Criteria for diagnosis includes upright P wave in leads I and II (can be more vertical than normal) that remains similar or identical to P wave during normal heart rate	P wave morphology during tachycardia is different than P wave during normal heart rate	P wave morphology during tachycardia is different than P wave during normal heart rate
P wave upright in lead aVL and biphasic in lead V1	N/A	Heart rate > 150 beats/minute
P wave amplitude in inferior leads increases as sinus rate increases (due to activation originating from more superior aspect of right atrium)	N/A	Paroxysmal tachycardia
In sinus node reentrant tachycardia, RP interval may be longer than during sinus rate	N/A	Negative P wave in lead aVL or entirely positive P wave in lead V1
Abbreviations: ECG, electrocardiogram; N/A, not applicable.

• ECG monitoring (such as Holter monitoring)
  • ambulatory ECG monitoring useful to determine if symptoms associated with sinus tachycardia or if other arrhythmias present
  • in patients with suspected IST
    • 24-hour Holter monitor might be useful (HRS Class IIb, Level E) to confirm diagnosis
    • mean 24-hour heart rate > 90 beats/minute not due to primary cause suggests IST
  • consider 24-hour Holter monitor for select patients with suspected POTS, though clinical efficacy is uncertain (HRS Class IIb, Level E)
  • 24-hour or 48-hour Holter monitor in patients with SNRT might show short sudden bursts of sinus tachycardia triggered and/or terminated by premature atrial beats
• Cardiac event recorders or implantable monitors may be needed in patients with infrequent palpitations and suspected SNRT
• Exercise ECG testing
  • consider exercise testing in patients with suspected IST (HRS Class IIb, Level E) to document exaggerated sinus tachycardia in response to exertion
  • consider exercise testing for select patients with suspected POTS (HRS Class IIb, Level E), though clinical efficacy is uncertain

Blood Tests

• In patients with suspected inappropriate sinus tachycardia
  • blood tests to rule out causes of normal sinus tachycardia
    • complete blood count and thyroid function test might be useful (HRS Class IIa, Level E)
    • serum or urine drug screening might be useful (HRS Class IIb, Level E)
  • diagnosis of inappropriate sinus tachycardia requires exclusion of primary cause of tachycardia, such as hyperthyroidism or anemia (J Am Coll Cardiol 2016 Apr 5;67(13):e27)
• Complete blood count and thyroid function test can be useful for selected patients being assessed for postural orthostatic tolerance syndrome (POTS) (HRS Class IIa, Level E).

Autonomic Testing

• Autonomic tests that evaluate cardiovascular autonomic reflexes include heart rate responses to deep breathing, standing, Valsalva maneuver, and cold face test (diving test)
• Consider autonomic testing in select patients with:
  • suspected inappropriate sinus tachycardia (IST) (HRS Class IIb, Level E)
  • suspected postural orthostatic tachycardia syndrome (POTS) (HRS Class IIb, Level E)
• Autonomic testing should not be routinely performed due to uncertain clinical efficacy.

Tilt Testing

• Consider tilt-table testing in select patients with suspected postural orthostatic tachycardia syndrome (POTS) (HRS Class IIb, Level E), such as patients with clinical features of POTS but normal orthostatic vitals.
• Increase in heart rate ≥ 30 beats/minute (> 40 beats/minute for patients < 20 years old) without orthostatic hypotension within 10 minutes of upright posture from supine position suggests POTS (Curr Neurol Neurosci Rep 2015 Sep;15(9):60).
• Immediate increase in heart rate with tilting may be observed in patients with inappropriate sinus tachycardia (J Am Coll Cardiol 2013 Feb 26;61(8):793).Electrophysiology Studies

• Electrophysiology studies not useful for diagnosing inappropriate sinus tachycardia (J Am Coll Cardiol 2013 Feb 26;61(8):793).
• Electrophysiology studies might be needed to differentiate sinus tachycardia from other arrhythmias (such as right upper pulmonary vein tachycardia and atrial tachycardia originating from crista terminalis or sinoatrial node) if electrocardiogram unable to identify arrhythmia.

Management

Management for Normal Sinus Tachycardia (NST)

• Treat reversible cause of sinus tachycardia (HRS Class I, Level E), such as thyroid disease, medication causes, or hypovolemia.
• NST typically resolves with correction of underlying cause (J Am Coll Cardiol 2016 Apr 5;67(13):e27)
• NST triggered by emotion or physical exertion usually responds to reassurance

Management for Inappropriate Sinus Tachycardia (IST)

• Treatment intended for symptom reduction and treatment of tachycardia alone may not improve symptoms
• Treatment in asymptomatic patients controversial as treatment side effects may be worse than burden of IST (J Am Coll Cardiol 2013 Feb 26;61(8):793)
• Close follow-up with attention and communication about patient symptoms reported to improve outcomes
• Lifestyle modifications
  • lifestyle changes can be discussed early in treatment
  • exercise training may be beneficial, but clinical efficacy not proven
  • triggers in diet (such as caffeine or alcohol) that can cause sinus tachycardia may be eliminated or reduced (J Am Coll Cardiol 2013 Feb 26;61(8):793)
• Heart Rhythm Society (HRS) recommendations
  • ivabradine can be useful for IST (HRS Class IIa, Level B-R) at dose 5-7.5 mg twice daily
  • sinus node modification, surgical ablation, and sympathetic denervation are not recommended as part of routine care for IST (HRS Class III, Level E)
• American College of Cardiology/American Heart Association/Heart Rhythm Society (ACC/AHA/HRS) recommendations
  • no specific recommendations for acute management
  • ongoing management for symptomatic patients
    • ivabradine is reasonable (ACC/AHA/HRS Class IIa, Level B-R)
    • beta-blockers may be considered (ACC/AHA/HRS Class IIb, Level C-LD)
    • combination of ivabradine and beta-blockers may be considered (ACC/AHA/HRS Class IIb, Level C-LD), especially if symptoms refractory to single drug regimen, but monitor closely for bradycardia
    • sinus node modification should be considered only for patients with high symptom burden despite medication therapy after discussion that risks may outweigh benefit
  • Reference - J Am Coll Cardiol 2016 Apr 5;67(13):e27
• Ivabradine contraindications and complications
  • ivabradine contraindicated in patients taking strong CYP3A4 inhibitors and in patients with liver dysfunction or severe renal dysfunction
  • ivabradine should be avoided in patients with hypotension and in patients who are pregnant or breastfeeding
  • ivabradine side effects may include excess bradycardia (especially if used in combination with beta-blockers or calcium channel blockers) and headaches
• Beta-blockers
  • beta-blockers may be useful in patients with tachycardia during exercise
  • beta-blockers reported to commonly be associated with side effects (such as fatigue)
• Combination of beta-blockers and benzodiazepine (for coexisting anxiety disorder) has been suggested
• Other treatments (such as fludrocortisone, volume expansion, pressure stockings, phenobarbital, clonidine, and erythropoietin) have been reported but safety and efficacy not established
• If radiofrequency catheter ablation being pursued for patients with high symptom burden despite medication therapy, postural orthostatic tachycardia syndrome (POTS) must be excluded due to potential for worsening of symptoms and hemodynamic compromise after ablation in patients with POTS³
• Evidence for medications

Management for Postural Orthostatic Tachycardia Syndrome (POTS)

• Start nonpharmacologic treatments first, including
  • increasing salt and fluid intake to increase blood volume (HRS Class IIb, Level E)
  • compression garments to reduce venous pooling
  • exercise program for reconditioning (HRS Class IIa, Level B-R)
    • exercise training, but not propranolol, reported to improve quality of life and increase aldosterone-to-renin ratio
• If nonpharmacologic treatments fail
  • stop medications that worsen POTS (such as norepinephrine transport inhibitors) (HRS Class III, Level B-R)
  • consider initiation of drug therapy that may include
    • fludrocortisone or pyridostigmine seem reasonable (HRS Class IIb, Level C)
    • midodrine or low-dose propranolol may be considered (HRS Class IIb, Level B-R)
    • clonidine or alpha-methyldopa in patients who have prominent hyperadrenergic features (HRS Class IIb, Level E)
• Acute IV saline (up to 2 L) is reasonable in patients who have short-term clinical decompensations (HRS Class IIa, Level C), but regular IV infusions of saline are not recommended (HRS Class III, Level E)
• See POTS for details

Management for Sinus Node Reentrant Tachycardia (SNRT)

• No specific medication recommended, but symptomatic patients may respond to
  • adenosine
  • amiodarone
  • beta-blockers
  • nondihydropyridine calcium-channel blockers
  • digoxin
  • Reference - J Am Coll Cardiol 2016 Apr 5;67(13):e27
• Adenosine reported to terminate atrial tachycardia in 6 patients with sinus node reentrant tachycardia in case series of 27 patients with atrial tachycardia confirmed with electrophysiology studies (Circulation 1994 Jun;89(6):2645)
• See also supraventricular tachycardia (SVT) for management of all focal atrial tachycardias (SNRT is an uncommon type of focal atrial tachycardia) (J Am Coll Cardiol 2016 Apr 5;67(13):e27)

Prognosis

• Normal sinus tachycardia (NST) generally benign, transient, and reversible (J Am Coll Cardiol 2013 Feb 26;61(8):793).
• Inappropriate sinus tachycardia (IST) generally benign (J Am Coll Cardiol 2013 Feb 26;61(8):793).
• IST triggered by virus may resolve quickly, but IST may persist ≥ 5 years in otherwise young and healthy patients.
• IST rarely associated with tachycardia-induced cardiomyopathy or life-threatening cardiovascular disease.