I'm in my mid-40s and I do cardio 3x weekly, and during my sessions, it's basically HIIT training. I try to keep my HR above 150 during my sessions, but it peaks in the low 180s intermittently.

Is this okay? My doctor noted potential concerns with getting my HR up that high, but it could be fine, she wasn't sure. I don't get any dizziness or anything (generally that happens if I sustain a heart rate above 185 for a bit). I'm not staying at 180 bpm, that's just the peak, I'm targeting an average HR of around 150-155 for my workouts.

In a 60 minute workout, I'll probably spend 10-15 minutes with my HR between 166 and 182 range.

Not sure if I should scale it down a bit or take it easier, or if this is fine.