Inappropriate sinus tachycardia


Inappropriate sinus tachycardia is a rare type of cardiac arrhythmia within the category of supraventricular tachycardia. IST may be caused by the sinus node itself having an abnormal structure or function, or it may be part of a problem called dysautonomia, a disturbance and/or failure of the autonomic nervous system. Research into the mechanism and etiology of inappropriate sinus tachycardia is ongoing.
IST is viewed by most to be a benign condition in the long-term. Symptoms of IST, however, may be distracting and warrant treatment. The heart is a strong muscle and typically can sustain the higher-than-normal heart rhythm, though monitoring the condition is generally recommended.
The mechanism and primary etiology of inappropriate sinus tachycardia has not been fully elucidated. An autoimmune mechanism has been suggested, as several studies have detected autoantibodies that activate beta adrenoreceptors in some patients. The mechanism of the arrhythmia primarily involves the sinus node and peri-nodal tissue and does not require the AV node for maintenance. Treatments in the form of pharmacological therapy or catheter ablation are available, but the condition is currently difficult to treat successfully.

Symptoms

Symptoms reported by patients vary in frequency and severity. They may include:
No formal diagnostic criteria exist. A diagnosis of inappropriate sinus tachycardia is primarily one of exclusion, and the following may be observed:
IST has been treated both pharmacologically and invasively, with varying degrees of success. IST, in and of itself, is not indicative of higher rates of mortality, and non-treatment is an option chosen by many if they have minimal symptoms.
Some types of medication tried by cardiologists and other physicians include: beta blockers, selective sinus node If channel inhibitors, calcium channel blockers, and antiarrhythmic agents. Some SSRI drugs are also occasionally tried, as are treatments more commonly used to treat postural orthostatic tachycardia syndrome, such as fludrocortisone.
Invasive treatments include forms of catheter ablation such as sinus node modification, complete sinus node ablation, and AV node ablation in very resistant cases. However, invasive treatments can also make the symptoms worse.

Literature