Not experienced it, but I have been the person in the room monitoring the ECGs.
Basically - said this before and I will say it again, think of your heart as the boiler of your central heating system. It is basically a mechanical pump controlled by electrical circuits / timers.
There are several mechanisms that cause SVT but the most common is that there is an 'extra wire' that bypasses the bit that times the heart rate.
On condition, Wolfe-Parkinson-White (WPW) has a visible extra bundle of cells called the bundle of Kent. This used to severely affect people's lives and in the 1970s/1980s some people had open heart surgery to physically cut out this extra bundle.
This was a major operation and was only done for severe symptoms, but with a ablation you can now burn, or freeze, or electrically destroy these cells from inside the heart via a tube (catheter) in your thigh.
Now the actual procedure will depend on the cause of the SVT. If you have WPW then it is straight forward, locate the extra cells and destroy them.
If it is not clear then it can take some time to 'map' the electrical activity. This can be done either as part of the ablation or as a separate EPS study. It is often done separately as it can take some time so is best not done at the start of a 'list'. Mapping involves recording electrograms from different areas of the heart and inducing the SVT.
If it is a bundle of cells that can be identified easily it is a straight forward procedure.
If it is more complex then it can take longer. Think a huge bundle of wires and you have to find the single one.
Sometimes the electrical system is completely destroyed and replaced by an artificial pacemaker, this is usually done as a planned procedure discussed with you before hand.
Very rarely, and I mean very, very as in it is possible but I have never seen it, it can be a complication of the procedure that more tissue is destroyed and you will be fitted with a pacemaker.
OK now your question about letting them go away on their own.
SVT is a fast heart rate that initiates above the ventricles, this means it is a lot less dangerous than ventricular tachycardia. SVT does reduce the amount of blood pumped around the body, the normal timing and pumping of the heart allows for maximum filling of the ventricles.
Isolated instances are very common. I have them when my thyroxine is too low (which is the opposite way round to the way it should be) and I've had 4 or 5 times in my life. The only reason I know it is SVT is because I could and did record my own ECG when I was symptomatic.
If they are causing problems then they should be treated. I assume the underlying cause has been investigated? Some people get SVT after drinking coffee for example, and the treatment for them is stop drinking coffee.
If you are having SVT there are a few ways to make it stop, some should only be attempted in a cath lab by a cardiologist.
One you can try at home is ice cream. Swallowing as large a chunk of ice cream as you can in one swallow can trigger your system back to it's non SVT state.
And if it doesn't work, well as long as you do not have an allergy to icecream no harm done.