So, valsalva done intentionally for a moment can convert back to a normal heart rhythm. (One side effect is it STOPS vocal chords from producing sound) valsalva done involuntarily is a fear response and it’s probably happening when you are talking. I think the arrhythmia and stutter are unrelated. But look up valsalva, stuttering on YouTube. There’s a good video from a William Parry, I think