From the Guidelines
Inappropriate sinus tachycardia (IST) and paroxysmal supraventricular tachycardia (PSVT) are distinct cardiac rhythm disorders that require different management approaches, with IST being a chronic condition characterized by a persistently elevated resting heart rate and PSVT being an episodic condition with sudden onset and termination of rapid heart rate.
Key Differences
- IST is characterized by a resting heart rate >100 bpm and a mean 24-h heart rate >90 bpm, without an identifiable cause, and is often associated with symptoms such as weakness, fatigue, and lightheadedness 1.
- PSVT, on the other hand, is a clinical syndrome characterized by the presence of a regular and rapid tachycardia of abrupt onset and termination, often triggered by specific factors like stress, caffeine, or exercise 1.
Diagnostic Considerations
- It is essential to distinguish IST from secondary causes of tachycardia, including hyperthyroidism, anemia, dehydration, pain, and use of exogenous substances, as well as from other forms of tachycardia, such as atrial tachycardia and sinus node reentrant tachycardia 1.
- A clinical history describing the pattern of episodes, duration, frequency, mode of onset, and possible triggers is crucial in diagnosing and managing these conditions 1.
Management Approaches
- IST management may include beta-blockers like metoprolol (25-100 mg twice daily) or ivabradine (2.5-7.5 mg twice daily), while PSVT treatment focuses on identifying and avoiding triggers, with short-acting beta-blockers used as needed during episodes.
- The distinction between IST and PSVT matters because IST requires ongoing management of a chronic condition, while PSVT involves preventing and treating discrete episodes, and both conditions require ruling out secondary causes of tachycardia before diagnosis 1.
From the Research
Inappropriate Sinus Tachycardia vs Paroxysmal Sinus Tachycardia
- Inappropriate sinus tachycardia (IST) is a clinical syndrome characterized by a resting heart rate of >100 beats per minute and an average 24-hour heart rate >90 bpm with distressing symptoms 2.
- The pathogenesis of IST is not well understood and is considered multifactorial, with autonomic dysfunction being the central abnormality 3.
- IST is a diagnosis of exclusion, and management presents a clinical challenge, with limited efficacy of lifestyle modifications and medical therapy 3, 4.
- Paroxysmal sinus tachycardia, on the other hand, refers to a sudden onset of sinus tachycardia that can be triggered by various factors, including stress, anxiety, or physical activity 5.
- While IST is often associated with distressing symptoms such as palpitations, chest pain, and fatigue, paroxysmal sinus tachycardia may not always be accompanied by symptoms 2, 5.
Key Differences
- The main difference between IST and paroxysmal sinus tachycardia is the duration and pattern of the tachycardia, with IST being a persistent condition and paroxysmal sinus tachycardia being an intermittent condition 5.
- IST is often associated with underlying autonomic dysfunction, while paroxysmal sinus tachycardia may be triggered by various factors, including physiological or pathological conditions 3, 5.
- The treatment approach for IST and paroxysmal sinus tachycardia may differ, with IST often requiring a more comprehensive and multidisciplinary approach, including lifestyle modifications, medical therapy, and possibly catheter or surgical ablation 3, 2, 6.
Diagnostic Considerations
- A thorough evaluation of secondary causes of tachycardia is required in the work-up of all cases of IST and paroxysmal sinus tachycardia, and if found, must be treated before a diagnosis can be made 6.
- The classification of sinus tachycardia, consideration of possible etiologies, as well as the decisions of when and how to intervene can be difficult, and may require a multidisciplinary approach 5.