IST Treatment and Questions

I was diagnosed with Inappropriate Sinus Tachycardia today. I had a 30-day auto-capture event monitor, which recorded almost daily events where my heart rate would spike to 180+ with no exertion whatsoever. My resting heart rate is always 120-130. The odd thing is, I have NEVER been aware of my heart rate at all... Even when my heart is racing, I don't "feel" it beating in my chest or anything like that. No chest pain, dizziness, etc. I only went to get my heart checked out because I used at heart rate monitor at the gym and it was giving me readings of 215. Looking back through my medical records though, my heart rate has always been high; it's just that no one really looked in to it because I wasn't complaining about it.

Anyway, couple of questions....

When my doctor diagnosed me, I asked him if this was something I could just live with and forego treatment since I don't experience any bothersome symptoms. He said no, it is something that really does require treatment because it was harmful to my heart even if I wasn't experiencing any obvious symptoms. Everything I have read though makes it sound like IST isn't going to kill me if left untreated... Are there possible long-term negative side effects of living with a heart rate that high?


Also, I've gotten the impression that ablation is only considered if the IST is non-responsive to medications. However, my Doctor said that he doesn't like the side effects of beta blockers and would just rather do ablation first, without trying any medications. I am all for this because I don't like the idea of having to take a beta blocker for the rest of my life if ablation could offer a permanent fix (well, maybe semi-permanent). Has anyone else skipped the medication route and just gone straight to ablation?

[is_something_wrong]

IST can vary greatly. Where some people just have a slightly elevated heart rate that causes no problems what so ever, some people have a far higher heart rate, and yes, a resting heart rate in the 120-130s will with time cause the heart to get an overload in pumping volume, which may cause the heart muscle to adapt in an inappropriate manner.

Just as high blood pressure (and heavy weightlifting) will make the heart walls thicken, in order to work against higher resistance, the heart will adapt to a higher cardiac output by increasing its inner space, and the heart muscle may dilate, which may with time (months, years or decades, impossible to say) cause heart failure (also known as dilated cardiomyopathy or tachycardia induced cardiomyopathy, often shortened tachycardiomyopathy).

There are other important things to remember. Often, IST is not actually caused by the sinus node, but rather another spot close to the sinus node, making the arrhythmia mimic sinus tachycardia on EKG, and in those cases the diagnosis is atrial tachycardia, not sinus tachycardia. Also, all "appropriate" causes of sinus tachycardia must be eliminated.

People with IST often struggle with low blood pressure, so beta blockers (especially the selective ones) may cause dizziness. Non-selective beta blockers can be more effective (I'm not a doctor, so what I say is strictly generally spoken and not related to your case). Another alternative is a selective sinus node inhibitor; ivabradine. It doesn't affect other parts of the heart than the sinus node.

IST can be caused both by cardiac abnormalities and abnormalities (dysregulation) in the autonomic nerve system, such as low tension in the blood vessels. An ultrasound of the heart may be appropriate to determine of your cardiac function is OK or the heart races to compensate, and to determine if your heart has suffered any damage from the rapid heart rate.

Ablations for IST are fairly new and the effect may go away, or the sinus node can be destroyed which puts someone in need of a pacemaker (which is actually not much of a crisis, by the way, and it is an alternative anyway if everything else should fail).

In my country, beta blockers or ivabradine is standard treatment for IST. I don't think they do sinus node modification (ablation). But an EP study will determine if the cause is in the sinus node or not. If you actually have an atrial tachycardia, treatment is fairly easy I think.

Good luck :)

[gracee06]

Thank you! That was really, really helpful.

[gubgub21]

i skipped right to get the ablations.. i think its smarter for the long run so then you dont have to worry about how the medicine can affect you long term...but im also 18 so my doctors dont want to put me on dangerous medicine..hope it helps!