Inappropriate sinus tachycardia (IST) refers to an abnormally high resting heart rate. An EKG (electrocardiogram) does not pick up IST as this occurs in the heart‘s sinus node - sort of the heart‘s natural pace maker.
It is not a well known condition and there isn’t a known cause for this abnormality. Although it is not life threatening and isn’t known to cause heart problems, it can be very debilitating.
As someone who has both IST and autonomic dysfunction, it can be difficult to determine which symptoms belong to which condition. Some of my symptoms include :
- High HR
- Palpitations
- Shortness of breath
- Struggle to exercise
- Becoming fatigued from doing the any activity
- HR reaching over 190 bpm without exercising
To reach this diagnosis and rule out other problems, i underwent :
- Testing for PoTS and autonomic dysfunction
- EKG and then 24/48/72 hour EKG
- Heart rate monitor for 7 days
- 24 hour BP monitor
- Echocardiogram
- Bubble study (based on symptoms after 4 years)
As i have other conditions including PoTS, my treatment options were limited to avoid flaring another condition and to avoid medication interaction. For this reason my IST and PoTS treatments have always been the same to treat both conditions without aggravating the other.
Over the course of 4 years, i have been on beta blockers, midodrine, non pharmacological methods (increase salt and water intake, supine exercises, hydrotherapy, compression garments), and as of last year, Ivabradine.
In my case nothing was helping so the Ivabradine, at the smallest dose possible, was a last resort before going onto more invasive treatment options. This would have been an ablation of the sinus node. Ablation refers to a minimally invasive surgery done via the groin and the sinus node either modified or destroed. As with any surgery, this comes with its own risks and it only considered after other treatment options are not working or cannot be used.
As with all posts - Please consult your doctor if you are having any symptoms !!