An increase of 35bpm, while it obviously scared you enough
to go
to the ER, posed absolutely no danger
to your heart. Think of times when you are not anxious but are very physically active, say out dancing. It's my guess that your heart rate climbs higher than 123bpm but because you're having fun and not thinking about your heart, you don't rush off to the ER, you go our for another dance! If you're doing yardwork or even housework, your HR will often climb.