During orgasm there are many physiological changes occur in body, rising heart rate is one of them.
SVT may have many triggers ( such as exercise, emotional stress etc).
I suggest you to be cautious in future about the same trigger you've mentioned.
Next Steps
During the attack of SVT do these things to lower your heart rate
-splash cold water over face
- do valsalva maneuver ( forcefully blow the air after closing nose & mouth)
- do carotid massage
- consult nearby physician as soon as possible
Health Tips
SVT is not a permanent disease, so do not excessively worry about it.
try doing yoga that will help to reduce stress in day to day life .
:)