SVT - Supraventricular Tachycardia

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SVT very broadly refers to uncontrolled rapid heart rhythms. In my case it means that I could riding along quite comfortably at 45km at say 160bpm and without warning my heart jumps to 240bpm. It is effectively a short circuit in the heart. Severity varies from person to person and the type of tachycardia they have.

When it strikes it feels like an asthma attack...short of breath, light headed and your heart feels like it has jumped into your throat. All of a sudden you feel really unfit and find yourself struggling. I have most likely had it most of my life and now that I reflect back there are the numerous occasions across several different sports where I can remember distinct moments of breathlessness. At the time I just put it down to being unfit although all the cycling I was doing must surely have put me towards the top quintile of fitness with a resting heart rate around 40bpm. It didn't make sense but I never thought it could be an issue with my ticker....so I ignored it.

It was only when a worked colleague suffering from SVT recognised the systems that I went to have a stress test (ie, running on a treadmill while under the watchful eye of a cardiologist). My SVT tends to kick in when I ease off after a particularly hard effort (eg, easing off after a fast climb). The test set about getting me to was going well my maximum heart rate of 188. It took 16mins to get there and then after holding it for a minute the treadmill was switched off. As soon as I eased up my heart went from 188 to 265bpm in a split second. The doctor's eyes almost popped out of his head.

I am amazed to hear how many ultra-fit individuals seem to be suffering from this. Triathletes and cyclists appear well represented. The best cases are probably champion triathlete Greg Welch (check out his book, "Heart of a Champion - the Greg Welch Story") and Stuart O'Grady.

I'd love to hear anyone else's experience and how they have coped. Mine is relatively manageable as long as I rest when it strikes....which means I get dropped from the pack every so often....

I have had this just once (to my knowledge), about 4 years ago. It wasn't after a hard effort, although I felt as if I had just been riding hard. I'd just left work, ambling along at about HR 100 BPM when all of a sudden - just as I was watching my HRM - it shot up to 190 BPM. I thought it was a defective HRM at first until I too became a little light headed and weak. I knew beforehand that my maz was around 190. I did go to the docs as I'd no idea what it was, and he told me the same as this - ST. Over the next 20 mins my HR gradually came down to normal and I started to feel OK again, but I had to ride very slowly for that period. Never happened since to my knowledge!

Sounds like a one off. I used to think my issue was interference with other Polar HR monitors in the pack...I actually think that if my stress test hadn't set off a tachycardia right at the end they would have just sent me on my way. Thanks for the feedback.



I have had this just once (to my knowledge), about 4 years ago. It wasn't after a hard effort, although I felt as if I had just been riding hard. I'd just left work, ambling along at about HR 100 BPM when all of a sudden - just as I was watching my HRM - it shot up to 190 BPM. I thought it was a defective HRM at first until I too became a little light headed and weak. I knew beforehand that my maz was around 190. I did go to the docs as I'd no idea what it was, and he told me the same as this - ST. Over the next 20 mins my HR gradually came down to normal and I started to feel OK again, but I had to ride very slowly for that period. Never happened since to my knowledge!

My HRM occasionally tells me that my HR is 230-240, for up to a minute at a time - Ive checked my pulse more than once before I realised that train overhead power lines seem to do it.