Inappropriate Sinus Tachycardia vs POTS

While many are familiar with Postural Orthostatic Tachycardia Syndrome (POTS), a lesser-known yet significant condition called Inappropriate Sinus Tachycardia (IST) exists within the realm of dysautonomia.

Symptoms such as heart palpitations, dizziness, feeling light-headed, and exhaustion are prevalent not only in POTS, a recognized autonomic nervous system disorder, but also in Inappropriate Sinus Tachycardia (IST). This complex, chronic condition demands precise diagnosis for effective management.

What is Inappropriate Sinus Tachycardia (IST)

IST is identified as a chronic, rare disorder characterized by a resting heart rate of over 100 BPM or an average heart rate exceeding 90 BPM within a 24-hour period.

Those with IST might constantly experience a high heart rate, triggered by minimal physical exertion or both scenarios. Sinus tachycardia refers to a rapid yet regular heart rhythm, indicating a consistent heartbeat without irregularities.

The range of symptoms includes palpitations, dizziness, chest discomfort, breath shortness, extreme fatigue, headache, and, in rare cases, fainting. The severity of symptoms varies widely, with some individuals being asymptomatic and others experiencing significant quality-of-life deterioration.

Who is at Risk for IST?

IST potentially affects about 1.2% of the population, with a tendency towards underdiagnosis. It predominantly impacts young women aged between 15 and 45, with women being significantly more likely to be diagnosed than men.

Dispelling the Myth: IST vs. Anxiety

IST is distinctly not a mental health issue. Its diagnosis is complicated by the overlap in symptoms with anxiety and depression, often leading to misdiagnosis. Addressing IST involves focusing on the underlying cause rather than solely on mental health support.

What Leads to IST?

The exact causes of IST are not fully understood but are thought to involve dysfunctions in the autonomic nervous system, which controls involuntary actions such as heart rate and digestion. This may result in abnormal cardiovascular responses, issues with the heart's natural pacemaker, or altered nervous system stimuli responses. Additionally, viral infections have been linked to the development of IST.

Distinguishing IST from POTS

IST and POTS share several symptoms, yet it's possible to have both conditions. IST is defined by specific heart rate criteria, while POTS is diagnosed based on a significant heart rate increase upon standing. An IST diagnosis means a patient may exhibit a consistently high resting heart rate, a characteristic not shared with POTS, where heart rates can normalize when lying down. Patients with both conditions tend to have a resting heart rate significantly above 100 BPM, with an additional increase upon standing.

Diagnosing and Managing IST

IST diagnosis is achieved through exclusion, with various tests conducted to eliminate other potential causes. Management strategies are still emerging, with suggestions including hydration, dietary adjustments, minimizing stimulant and alcohol intake, staying cool, using compression garments, regular exercise, and possibly medication.

The approach to managing IST is highly individualized, requiring adjustments and experimentation to find the most effective symptom management strategy.

‍